thinking about building another .308 with a 1-10 twist barrel. Anyone have any experience with what bullet weight would be optimal to get to 1000 yards?
-barrel length will probably be 20-22"
-barrel length will probably be 20-22"
- Thread starter craines51
- Start date
Re: 1/10 twist .308 to 1000yrds
175's work great and are what I shoot at a 1000. The 185's would be another good choice, they would take a little more elevation to get there but should cut the wind better. Donald
175's work great and are what I shoot at a 1000. The 185's would be another good choice, they would take a little more elevation to get there but should cut the wind better. Donald
Re: 1/10 twist .308 to 1000yrds
for a 20-22" barrel id go with the lapua 155 scenars or the seirra 155 palma matchkings. both are high in ballistics and will make the distance ss
for a 20-22" barrel id go with the lapua 155 scenars or the seirra 155 palma matchkings. both are high in ballistics and will make the distance ss
Re: 1/10 twist .308 to 1000yrds
I use 1-10 pretty much across the board and have no problem shooting anything to 1000 yards. I shoot everything from 155gr Scenars to 175gr SMK and they are both good to go at that range.
Its a good choice the 1/10
I use 1-10 pretty much across the board and have no problem shooting anything to 1000 yards. I shoot everything from 155gr Scenars to 175gr SMK and they are both good to go at that range.
Its a good choice the 1/10
Re: 1/10 twist .308 to 1000yrds
My 10 twist .308 loves the 185's... Did well with 175's and 190's too. I think it's a very versatile barrel.
My 10 twist .308 loves the 185's... Did well with 175's and 190's too. I think it's a very versatile barrel.
Re: 1/10 twist .308 to 1000yrds
Regardless of twist run the tables for the new Sierra 155 Palma #2156 or the 155 Berger full bore. Less recoil, almost same BC as 175MK. Just a thought, they work for me.
Regardless of twist run the tables for the new Sierra 155 Palma #2156 or the 155 Berger full bore. Less recoil, almost same BC as 175MK. Just a thought, they work for me.
Re: 1/10 twist .308 to 1000yrds
175smk's
175smk's
Re: 1/10 twist .308 to 1000yrds
what would be the pros or cons over using a 155 in a 10 twist over a 12 twist. Would one not be able to get more speed from a slower twist in a shorter bbl?
what would be the pros or cons over using a 155 in a 10 twist over a 12 twist. Would one not be able to get more speed from a slower twist in a shorter bbl?
Re: 1/10 twist .308 to 1000yrds
Be a man and use the big boys, that is the 208amax's or 210 Bergers!
I have a 20" 1:10 twist that'll get those out fast enough to remain supersonic to at least 1300 yards. That being said, if you don't want to go that heavy, 155 Scenars, and 175gr SMK's or 178Amax, 175 Bergers, most of that class of bullet and heavier will get you do 1K as long as you start them fast enough.
Branden
Be a man and use the big boys, that is the 208amax's or 210 Bergers!
I have a 20" 1:10 twist that'll get those out fast enough to remain supersonic to at least 1300 yards. That being said, if you don't want to go that heavy, 155 Scenars, and 175gr SMK's or 178Amax, 175 Bergers, most of that class of bullet and heavier will get you do 1K as long as you start them fast enough.
Branden
Re: 1/10 twist .308 to 1000yrds
For a 22" 1:10, the 175 or 185 grain range has lots of good options (I'd try the Berger 185's). We have had issues running the 155's as fast as we'd like to (3100+ in a 30" barrel) with the 1:10. In one major match a few years back, we had two projectiles come apart through the one Team guy's rifle with a 1:10, all the other guys were running a 1:12 and had no issues.
Darrell
For a 22" 1:10, the 175 or 185 grain range has lots of good options (I'd try the Berger 185's). We have had issues running the 155's as fast as we'd like to (3100+ in a 30" barrel) with the 1:10. In one major match a few years back, we had two projectiles come apart through the one Team guy's rifle with a 1:10, all the other guys were running a 1:12 and had no issues.
Darrell
Re: 1/10 twist .308 to 1000yrds
I have a Savage 10FP LE2 which has the one in ten twist. Using 167 Scenars over 44 gr Varget gives me 2780 fps and last year i shot a 75-13 at 1000 yards to win our clubs 1000 yard competition.
I have a Savage 10FP LE2 which has the one in ten twist. Using 167 Scenars over 44 gr Varget gives me 2780 fps and last year i shot a 75-13 at 1000 yards to win our clubs 1000 yard competition.
Re: 1/10 twist .308 to 1000yrds
Don't rule out the 190 SMK and the 208 A-max. They run a little slower, but will have less wind drift than the 175's.
Don't rule out the 190 SMK and the 208 A-max. They run a little slower, but will have less wind drift than the 175's.
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">Don't rule out the 190 SMK and the 208 A-max. They run a little slower, but will have less wind drift than the 175's.
</div></div>
That reminds me, I have some 190SMk's that I have yet to try out in my rifle. Need to break them out and give them a shot over the winter.
Branden
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ChadTRG42</div><div class="ubbcode-body">Don't rule out the 190 SMK and the 208 A-max. They run a little slower, but will have less wind drift than the 175's.
</div></div>
That reminds me, I have some 190SMk's that I have yet to try out in my rifle. Need to break them out and give them a shot over the winter.
Branden
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I use 1-10 pretty much across the board and have no problem shooting anything to 1000 yards. I shoot everything from 155gr Scenars to 175gr SMK and they are both good to go at that range.
Its a good choice the 1/10
</div></div>
Frank - is that the Kreiger or have you changed barrels?
I'm still thinking about one, but with my cashflow has been going into my 1903a3...
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I use 1-10 pretty much across the board and have no problem shooting anything to 1000 yards. I shoot everything from 155gr Scenars to 175gr SMK and they are both good to go at that range.
Its a good choice the 1/10
</div></div>
Frank - is that the Kreiger or have you changed barrels?
I'm still thinking about one, but with my cashflow has been going into my 1903a3...
Re: 1/10 twist .308 to 1000yrds
Back on topics - I've shot 155's and 175's (SMK only) both go to 1000 just fine in a 1/12, don't see why 1/10 would change that.
I had a 1/11.25 twist on my 27.25" palma barrel tho, straight shooter, and again as everyone else said the 175's do better in wind.
I understand Palma guys are using 30" 1/13 twist now with the 155's...(???)
Back on topics - I've shot 155's and 175's (SMK only) both go to 1000 just fine in a 1/12, don't see why 1/10 would change that.
I had a 1/11.25 twist on my 27.25" palma barrel tho, straight shooter, and again as everyone else said the 175's do better in wind.
I understand Palma guys are using 30" 1/13 twist now with the 155's...(???)
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ArcticLight</div><div class="ubbcode-body">
I understand Palma guys are using 30" 1/13 twist now with the 155's...(???) </div></div>
True statement. That is now the big debate in F-T/R; 1:11.5, 1:12, or 1:13 for the 155's (or 155.5's). While the Palma guys seem to like the 1:13 twist, they are shooting on a target that is twice the diameter of the F-Class Target (10" "X" instead of 5" at 1000 yards), a little more room for error (although with sling and irons, not necessarily easier
). Personally, I think the answer is somewhere between 1:11 and 1:12, basically over-revving the 155's to ensure max stability at 1000 and beyond, but only time will tell.
Darrell
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ArcticLight</div><div class="ubbcode-body">
I understand Palma guys are using 30" 1/13 twist now with the 155's...(???) </div></div>
True statement. That is now the big debate in F-T/R; 1:11.5, 1:12, or 1:13 for the 155's (or 155.5's). While the Palma guys seem to like the 1:13 twist, they are shooting on a target that is twice the diameter of the F-Class Target (10" "X" instead of 5" at 1000 yards), a little more room for error (although with sling and irons, not necessarily easier
Darrell
Re: 1/10 twist .308 to 1000yrds
190 SMK's at 2625 will work wonders.
190 SMK's at 2625 will work wonders.
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Darrell Buell</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ArcticLight</div><div class="ubbcode-body">
I understand Palma guys are using 30" 1/13 twist now with the 155's...(???) </div></div>
True statement. That is now the big debate in F-T/R; 1:11.5, 1:12, or 1:13 for the 155's (or 155.5's). While the Palma guys seem to like the 1:13 twist, they are shooting on a target that is twice the diameter of the F-Class Target (10" "X" instead of 5" at 1000 yards), a little more room for error (although with sling and irons, not necessarily easier ). Personally, I think the answer is somewhere between 1:11 and 1:12, basically over-revving the 155's to ensure max stability at 1000 and beyond, but only time will tell.
Darrell</div></div>
Just a question, do you think you'd find the 155's over-revving, as you put it, being counter productive to stability over the long haul? Or is it not enough to make a difference?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Darrell Buell</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ArcticLight</div><div class="ubbcode-body">
I understand Palma guys are using 30" 1/13 twist now with the 155's...(???) </div></div>
True statement. That is now the big debate in F-T/R; 1:11.5, 1:12, or 1:13 for the 155's (or 155.5's). While the Palma guys seem to like the 1:13 twist, they are shooting on a target that is twice the diameter of the F-Class Target (10" "X" instead of 5" at 1000 yards), a little more room for error (although with sling and irons, not necessarily easier
Darrell</div></div>
Just a question, do you think you'd find the 155's over-revving, as you put it, being counter productive to stability over the long haul? Or is it not enough to make a difference?
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: s.i.t.</div><div class="ubbcode-body">for a 20-22" barrel id go with the lapua 155 scenars ....</div></div> my 20" FN SPR is a hammer with those
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: s.i.t.</div><div class="ubbcode-body">for a 20-22" barrel id go with the lapua 155 scenars ....</div></div> my 20" FN SPR is a hammer with those
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Darrell Buell</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ArcticLight</div><div class="ubbcode-body">
I understand Palma guys are using 30" 1/13 twist now with the 155's...(???) </div></div>
True statement. That is now the big debate in F-T/R; 1:11.5, 1:12, or 1:13 for the 155's (or 155.5's). While the Palma guys seem to like the 1:13 twist, they are shooting on a target that is twice the diameter of the F-Class Target (10" "X" instead of 5" at 1000 yards), a little more room for error (although with sling and irons, not necessarily easier ). Personally, I think the answer is somewhere between 1:11 and 1:12, basically over-revving the 155's to ensure max stability at 1000 and beyond, but only time will tell.
Darrell</div></div>
Just a question, do you think you'd find the 155's over-revving, as you put it, being counter productive to stability over the long haul? Or is it not enough to make a difference? </div></div>
The 155 scenars are longer than the 175 grain Sierra matchking. I highly doubt a 1 in 10 will over "rev" them as you say. They're really long.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Darrell Buell</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ArcticLight</div><div class="ubbcode-body">
I understand Palma guys are using 30" 1/13 twist now with the 155's...(???) </div></div>
True statement. That is now the big debate in F-T/R; 1:11.5, 1:12, or 1:13 for the 155's (or 155.5's). While the Palma guys seem to like the 1:13 twist, they are shooting on a target that is twice the diameter of the F-Class Target (10" "X" instead of 5" at 1000 yards), a little more room for error (although with sling and irons, not necessarily easier
Darrell</div></div>
Just a question, do you think you'd find the 155's over-revving, as you put it, being counter productive to stability over the long haul? Or is it not enough to make a difference? </div></div>
The 155 scenars are longer than the 175 grain Sierra matchking. I highly doubt a 1 in 10 will over "rev" them as you say. They're really long.
Re: 1/10 twist .308 to 1000yrds
I shoot 155gr Scenars from my Gladius, 18.5" Bartlein with a 1/10 twist and they absolutely work great.
Less wind drift then using 175gr SMKs, and flatter shooting.
There is no issue using a 155gr bullet in a short barreled 1/10.
I shoot 155gr Scenars from my Gladius, 18.5" Bartlein with a 1/10 twist and they absolutely work great.
Less wind drift then using 175gr SMKs, and flatter shooting.
There is no issue using a 155gr bullet in a short barreled 1/10.
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body">
Just a question, do you think you'd find the 155's over-revving, as you put it, being counter productive to stability over the long haul? Or is it not enough to make a difference? </div></div>
When running a 155 grain Berger (VLD or Fullbore) at 3125 through a 1:12, we see that it takes 200-300 yards for the accuracy potential of a load to be seen. For a given load, you may see a .66" group at 100 yards, the same .66" group at 200 yards, and a .75" group at 300 yards. For these rifles and loads, we never shoot them closer than 300 yards, more common is 800-1000 yards. All of our load testing (accuracy, not chronograph) is done prone off a bipod at 300 yards.
Reading Litz's excellent book on ballistics, it appears that by giving the bullets "extra" RPM, we may increase the drag at the end of it's flight, but it seems to be pretty negligable.
LL: We had bullet failures when we got 155's up over 3200fps through a 1:10. The over the top velocities were mainly caused by: high starting velocity (3120), temperature sensitive powder, and a receiver hot enough to fry eggs on in the middle of a long range match. That said, when the velocities were below 3100, the accuracy of the 155's through a 1:10 were excellent. I don't guess anyone's likely to see velocities that high with a 22" barrel, so pretty much a non-issue.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body">
Just a question, do you think you'd find the 155's over-revving, as you put it, being counter productive to stability over the long haul? Or is it not enough to make a difference? </div></div>
When running a 155 grain Berger (VLD or Fullbore) at 3125 through a 1:12, we see that it takes 200-300 yards for the accuracy potential of a load to be seen. For a given load, you may see a .66" group at 100 yards, the same .66" group at 200 yards, and a .75" group at 300 yards. For these rifles and loads, we never shoot them closer than 300 yards, more common is 800-1000 yards. All of our load testing (accuracy, not chronograph) is done prone off a bipod at 300 yards.
Reading Litz's excellent book on ballistics, it appears that by giving the bullets "extra" RPM, we may increase the drag at the end of it's flight, but it seems to be pretty negligable.
LL: We had bullet failures when we got 155's up over 3200fps through a 1:10. The over the top velocities were mainly caused by: high starting velocity (3120), temperature sensitive powder, and a receiver hot enough to fry eggs on in the middle of a long range match. That said, when the velocities were below 3100, the accuracy of the 155's through a 1:10 were excellent. I don't guess anyone's likely to see velocities that high with a 22" barrel, so pretty much a non-issue.
Re: 1/10 twist .308 to 1000yrds
OK, this 10-twist bandwagon is officially full, so I'll be the lone dissenter:
You don't really need a 1 in 10, unless and until you chop the barrel to under twenty inches or you want to shoot the real heavy subsonics. An 11-twist should suffice for everything, even up to the 220 grainer subsonics, provided that you are not shooting them in the dead of winter.
And increased velocity is not available by reducing the twist rate: twist has so little effect on velocity that I defy anyone to be able to measure it, never mind tell the difference on a chronograph.
OK, this 10-twist bandwagon is officially full, so I'll be the lone dissenter:
You don't really need a 1 in 10, unless and until you chop the barrel to under twenty inches or you want to shoot the real heavy subsonics. An 11-twist should suffice for everything, even up to the 220 grainer subsonics, provided that you are not shooting them in the dead of winter.
And increased velocity is not available by reducing the twist rate: twist has so little effect on velocity that I defy anyone to be able to measure it, never mind tell the difference on a chronograph.
Re: 1/10 twist .308 to 1000yrds
Guys the theory of over stabilizing a bullet is half true. While you cannot over stabilize a bullet a couple of negatives can happen and to me it has to do with poor quality ammo. Excessive run out in your loaded ammo or the bullet itself.
Take a 147gr. ball ammo. This is a good example of poor quality bullet/ammo. The more run out the ammo/bullet has a faster twist will exaggerate it. This will show on the target accuracy wise.
Also a possibility with a faster twist is when you shoot a thinner jacket bullet. The higher rpm could have an effect on the bullet itself and can possibly cause the bullet to come a part. I believe there is more to it than just this one factor that causes bullet failure. Velocity plays a part as well.
I always tell guys this. If you are shooting good quality ammo/bullets a faster twist doesn't effect you accuracy wise as much as people thinks it does. The key is shooting/using good quality components.
Yes most of the palma guys shoot a 13 twist barrel. The other reason for this is some countries still give they're shooters ball ammo. The slower twist will shoot the ball ammo better than a faster twist accuracy wise. Several years ago we made some 13 twist M14 match rifle barrels when we still worked at Krieger for some Navy shooters. I asked the guy the only reason you would want a 13 twist is because you are shooting ball ammo. He said exactly. When Clinton was in office they cut they're budgets so much they couldn't afford to give new match shooters a good gun and good ammo. So for the new shooters they built them a good gun and they used delinked M60 ball ammo. When the shooters skill improved enough then they got a gun with a faster twist and match ammo. The slower twist helped the crummy ammo situation they had.
Later, Frank
Bartlein Barrels
Guys the theory of over stabilizing a bullet is half true. While you cannot over stabilize a bullet a couple of negatives can happen and to me it has to do with poor quality ammo. Excessive run out in your loaded ammo or the bullet itself.
Take a 147gr. ball ammo. This is a good example of poor quality bullet/ammo. The more run out the ammo/bullet has a faster twist will exaggerate it. This will show on the target accuracy wise.
Also a possibility with a faster twist is when you shoot a thinner jacket bullet. The higher rpm could have an effect on the bullet itself and can possibly cause the bullet to come a part. I believe there is more to it than just this one factor that causes bullet failure. Velocity plays a part as well.
I always tell guys this. If you are shooting good quality ammo/bullets a faster twist doesn't effect you accuracy wise as much as people thinks it does. The key is shooting/using good quality components.
Yes most of the palma guys shoot a 13 twist barrel. The other reason for this is some countries still give they're shooters ball ammo. The slower twist will shoot the ball ammo better than a faster twist accuracy wise. Several years ago we made some 13 twist M14 match rifle barrels when we still worked at Krieger for some Navy shooters. I asked the guy the only reason you would want a 13 twist is because you are shooting ball ammo. He said exactly. When Clinton was in office they cut they're budgets so much they couldn't afford to give new match shooters a good gun and good ammo. So for the new shooters they built them a good gun and they used delinked M60 ball ammo. When the shooters skill improved enough then they got a gun with a faster twist and match ammo. The slower twist helped the crummy ammo situation they had.
Later, Frank
Bartlein Barrels
Re: 1/10 twist .308 to 1000yrds
If you already have a .308, my advice would be to give the .30-'06 a try. The 1:10 twist and same bullets should work, and work better the longer the distances grow. In close, the differences between the chamberings are smaller, but as the distances stretch more, the .30-'06 comes further and further into its prime as many shooters here can both attest, and can help you with your goals. While recoil increases some, it's not excessive with a properly scaled LR-specific firearm.
Greg
If you already have a .308, my advice would be to give the .30-'06 a try. The 1:10 twist and same bullets should work, and work better the longer the distances grow. In close, the differences between the chamberings are smaller, but as the distances stretch more, the .30-'06 comes further and further into its prime as many shooters here can both attest, and can help you with your goals. While recoil increases some, it's not excessive with a properly scaled LR-specific firearm.
Greg
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Downzero</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Darrell Buell</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ArcticLight</div><div class="ubbcode-body">
I understand Palma guys are using 30" 1/13 twist now with the 155's...(???) </div></div>
True statement. That is now the big debate in F-T/R; 1:11.5, 1:12, or 1:13 for the 155's (or 155.5's). While the Palma guys seem to like the 1:13 twist, they are shooting on a target that is twice the diameter of the F-Class Target (10" "X" instead of 5" at 1000 yards), a little more room for error (although with sling and irons, not necessarily easier ). Personally, I think the answer is somewhere between 1:11 and 1:12, basically over-revving the 155's to ensure max stability at 1000 and beyond, but only time will tell.
Darrell</div></div>
Just a question, do you think you'd find the 155's over-revving, as you put it, being counter productive to stability over the long haul? Or is it not enough to make a difference? </div></div>
The 155 scenars are longer than the 175 grain Sierra matchking. I highly doubt a 1 in 10 will over "rev" them as you say. They're really long.</div></div>
That's a good point. I don't shoot them. But, the 123 Scenars I do shoot in 6.5 are long as all get out too. That would make sense.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Downzero</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sandwarrior</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Darrell Buell</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ArcticLight</div><div class="ubbcode-body">
I understand Palma guys are using 30" 1/13 twist now with the 155's...(???) </div></div>
True statement. That is now the big debate in F-T/R; 1:11.5, 1:12, or 1:13 for the 155's (or 155.5's). While the Palma guys seem to like the 1:13 twist, they are shooting on a target that is twice the diameter of the F-Class Target (10" "X" instead of 5" at 1000 yards), a little more room for error (although with sling and irons, not necessarily easier
Darrell</div></div>
Just a question, do you think you'd find the 155's over-revving, as you put it, being counter productive to stability over the long haul? Or is it not enough to make a difference? </div></div>
The 155 scenars are longer than the 175 grain Sierra matchking. I highly doubt a 1 in 10 will over "rev" them as you say. They're really long.</div></div>
That's a good point. I don't shoot them. But, the 123 Scenars I do shoot in 6.5 are long as all get out too. That would make sense.
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I shoot 155gr Scenars from my Gladius, 18.5" Bartlein with a 1/10 twist and they absolutely work great.
Less wind drift then using 175gr SMKs, and flatter shooting.
There is no issue using a 155gr bullet in a short barreled 1/10. </div></div>
Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I shoot 155gr Scenars from my Gladius, 18.5" Bartlein with a 1/10 twist and they absolutely work great.
Less wind drift then using 175gr SMKs, and flatter shooting.
There is no issue using a 155gr bullet in a short barreled 1/10. </div></div>
Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K.
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K. </div></div>
Wind drift is determined by lag time, not time of flight. Lag time is the difference between the actual time of flight and the theoretical time of flight in a vacuum (distance/muzzle velocity).
Check out chapter 5 of Applied Ballistics by Bryan Litz.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K. </div></div>
Wind drift is determined by lag time, not time of flight. Lag time is the difference between the actual time of flight and the theoretical time of flight in a vacuum (distance/muzzle velocity).
Check out chapter 5 of Applied Ballistics by Bryan Litz.
Re: 1/10 twist .308 to 1000yrds
Which is why higher BC bullets, those retaining a greater percentage of their muzzle velocity, drift less in the wind compared to lower BC bullets, even if the latter start out faster.
Which is why higher BC bullets, those retaining a greater percentage of their muzzle velocity, drift less in the wind compared to lower BC bullets, even if the latter start out faster.
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K. </div></div>
Wind drift is determined by lag time, not time of flight. Lag time is the difference between the actual time of flight and the theoretical time of flight in a vacuum (distance/muzzle velocity).
Check out chapter 5 of Applied Ballistics by Bryan Litz. </div></div>
Can you explain how that would apply in this case:
A 240 SMK at 1050 fps vs a 240 SMK at 2700 fps, both shot at 300 yards, in a 10 mph full-value wind?
My math says the 240 at 2700 will drift less, despite shedding more velocity, thus having a longer lag time.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K. </div></div>
Wind drift is determined by lag time, not time of flight. Lag time is the difference between the actual time of flight and the theoretical time of flight in a vacuum (distance/muzzle velocity).
Check out chapter 5 of Applied Ballistics by Bryan Litz. </div></div>
Can you explain how that would apply in this case:
A 240 SMK at 1050 fps vs a 240 SMK at 2700 fps, both shot at 300 yards, in a 10 mph full-value wind?
My math says the 240 at 2700 will drift less, despite shedding more velocity, thus having a longer lag time.
Re: 1/10 twist .308 to 1000yrds
Lag time + theoretical TOF = true TOF.
True TOF corerelates to drift, given equal bullets in equal atomsperic conditions.
Lag time + theoretical TOF = true TOF.
True TOF corerelates to drift, given equal bullets in equal atomsperic conditions.
Re: 1/10 twist .308 to 1000yrds
240 smk G7 .332, 300 yards, 10mph cross wind
2700 fps: tof .3612, lag time .0279, drift 4.92"
1050 fps: tof .8976, lag time .0404, drift 7.17"
Ratios: tof .4024,lag time .6906, drift .6862
as you can see, drift is proportional to lag time, and not time of flight.
calculations from litz point mass solver.
240 smk G7 .332, 300 yards, 10mph cross wind
2700 fps: tof .3612, lag time .0279, drift 4.92"
1050 fps: tof .8976, lag time .0404, drift 7.17"
Ratios: tof .4024,lag time .6906, drift .6862
as you can see, drift is proportional to lag time, and not time of flight.
calculations from litz point mass solver.
Re: 1/10 twist .308 to 1000yrds
Ok, I think I understand. Thanks.
Ok, I think I understand. Thanks.
Re: 1/10 twist .308 to 1000yrds
Some number crunching in Quicktarget, with easy multiples,
240SMK, 1000fps, 1000 yards (3000ft) TOF 3.37 sec, .37 sec lag, drift 65.2"
240SMK, 3000fps, 1000 yards (3000ft) TOF 1.25 sec, .25 sec lag, drift 43.2"
Some number crunching in Quicktarget, with easy multiples,
240SMK, 1000fps, 1000 yards (3000ft) TOF 3.37 sec, .37 sec lag, drift 65.2"
240SMK, 3000fps, 1000 yards (3000ft) TOF 1.25 sec, .25 sec lag, drift 43.2"
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body">240 smk G7 .332, 300 yards, 10mph cross wind
2700 fps: tof .3612, lag time .0279, drift 4.92"
1050 fps: tof .8976, lag time .0404, drift 7.17"
Ratios: tof .4024,lag time .6906, drift .6862
<span style="font-weight: bold">as you can see, drift is proportional to lag time, and not time of flight.</span>
calculations from litz point mass solver. </div></div>
May I ask the dumb question here? I get "Time of flight", but what is "Lag Time"?
Thanks,
-Pat
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body">240 smk G7 .332, 300 yards, 10mph cross wind
2700 fps: tof .3612, lag time .0279, drift 4.92"
1050 fps: tof .8976, lag time .0404, drift 7.17"
Ratios: tof .4024,lag time .6906, drift .6862
<span style="font-weight: bold">as you can see, drift is proportional to lag time, and not time of flight.</span>
calculations from litz point mass solver. </div></div>
May I ask the dumb question here? I get "Time of flight", but what is "Lag Time"?
Thanks,
-Pat
Re: 1/10 twist .308 to 1000yrds
Here are some calculations I ran. It looks like the 175 SMK is the clear looser.
1000 yards, 10mph cross wind
155 scenar, G7 .236, 2950fps; drop 324" drift 94"
175 berger LRBT, G7 .264, 2650fps; drop 386" drift 96"
175 SMK, G7 .243, 2650fps; drop 421" drift 109"
185 berger LRBT, G7 .283, 2575fps; drop 393" drift 91"
208 amax, G7 .324, 2450fps; drop 406" drift 82"
Here are some calculations I ran. It looks like the 175 SMK is the clear looser.
1000 yards, 10mph cross wind
155 scenar, G7 .236, 2950fps; drop 324" drift 94"
175 berger LRBT, G7 .264, 2650fps; drop 386" drift 96"
175 SMK, G7 .243, 2650fps; drop 421" drift 109"
185 berger LRBT, G7 .283, 2575fps; drop 393" drift 91"
208 amax, G7 .324, 2450fps; drop 406" drift 82"
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: He_Shoot_Me</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body">240 smk G7 .332, 300 yards, 10mph cross wind
2700 fps: tof .3612, lag time .0279, drift 4.92"
1050 fps: tof .8976, lag time .0404, drift 7.17"
Ratios: tof .4024,lag time .6906, drift .6862
<span style="font-weight: bold">as you can see, drift is proportional to lag time, and not time of flight.</span>
calculations from litz point mass solver. </div></div>
May I ask the dumb question here? I get "Time of flight", but what is "Lag Time"?
Thanks,
-Pat </div></div>
In a vacuum, there would be no air resistance, and a bullet would maintain it's velocity. The theoretical time of flight can be calculated by dividing the distance traveled by the muzzle velocity.
In reality, the bullet starts slowing down immediately because of air resistance. The actual time of flight can e calculated by a ballistics program.
Lag time is the difference between the actual and theoretical time of flight, and is a measurement of the effect of air resistance on the bullet.
example: 240 SMK, mv: 2700, distance 300 yards.
300 yards=900 feet.
tof in vacuum is 900/2700=.333 seconds
actual tof from ballistics program .361 seconds
<span style="font-weight: bold">lag time=.361-.333=.028 seconds</span>
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: He_Shoot_Me</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body">240 smk G7 .332, 300 yards, 10mph cross wind
2700 fps: tof .3612, lag time .0279, drift 4.92"
1050 fps: tof .8976, lag time .0404, drift 7.17"
Ratios: tof .4024,lag time .6906, drift .6862
<span style="font-weight: bold">as you can see, drift is proportional to lag time, and not time of flight.</span>
calculations from litz point mass solver. </div></div>
May I ask the dumb question here? I get "Time of flight", but what is "Lag Time"?
Thanks,
-Pat </div></div>
In a vacuum, there would be no air resistance, and a bullet would maintain it's velocity. The theoretical time of flight can be calculated by dividing the distance traveled by the muzzle velocity.
In reality, the bullet starts slowing down immediately because of air resistance. The actual time of flight can e calculated by a ballistics program.
Lag time is the difference between the actual and theoretical time of flight, and is a measurement of the effect of air resistance on the bullet.
example: 240 SMK, mv: 2700, distance 300 yards.
300 yards=900 feet.
tof in vacuum is 900/2700=.333 seconds
actual tof from ballistics program .361 seconds
<span style="font-weight: bold">lag time=.361-.333=.028 seconds</span>
Re: 1/10 twist .308 to 1000yrds
That makes perfect since. Thanks for taking the time to explain runngun, I appreciate it!
-Pat
That makes perfect since. Thanks for taking the time to explain runngun, I appreciate it!
-Pat
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K. </div></div>
Wind drift is determined by lag time, not time of flight. Lag time is the difference between the actual time of flight and the theoretical time of flight in a vacuum (distance/muzzle velocity).
Check out chapter 5 of Applied Ballistics by Bryan Litz. </div></div>
Lets just say that I am well aware of "true time of flight". I was not thinking in a vacuum!!!! Time of flight is the "total" time the projectile is exposed to the given conditions. The "lag-time", if you so wish to call it is simply part of the actual time of flight.
Also note, your g-7 data is not for the 155 smk and if you wish to use the g-7 data please use the new smk 2156c as it was the bullet I referenced. It's new BC is about 12% higher than the 2155.
If we are talking 155 smk vs. 175 smk the 155 wins to 1K any day of the week and that was the supportive information I was using to back the original post that I referenced.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K. </div></div>
Wind drift is determined by lag time, not time of flight. Lag time is the difference between the actual time of flight and the theoretical time of flight in a vacuum (distance/muzzle velocity).
Check out chapter 5 of Applied Ballistics by Bryan Litz. </div></div>
Lets just say that I am well aware of "true time of flight". I was not thinking in a vacuum!!!! Time of flight is the "total" time the projectile is exposed to the given conditions. The "lag-time", if you so wish to call it is simply part of the actual time of flight.
Also note, your g-7 data is not for the 155 smk and if you wish to use the g-7 data please use the new smk 2156c as it was the bullet I referenced. It's new BC is about 12% higher than the 2155.
If we are talking 155 smk vs. 175 smk the 155 wins to 1K any day of the week and that was the supportive information I was using to back the original post that I referenced.
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K. </div></div>
Wind drift is determined by lag time, not time of flight. Lag time is the difference between the actual time of flight and the theoretical time of flight in a vacuum (distance/muzzle velocity).
Check out chapter 5 of Applied Ballistics by Bryan Litz. </div></div>
Lets just say that I am well aware of "true time of flight". I was not thinking in a vacuum!!!! Time of flight is the "total" time the projectile is exposed to the given conditions. The "lag-time", if you so wish to call it is simply part of the actual time of flight.
Also note, your g-7 data is not for the 155 smk and if you wish to use the g-7 data please use the new smk 2156c as it was the bullet I referenced. It's new BC is about 12% higher than the 2155.
If we are talking 155 smk vs. 175 smk the 155 wins to 1K any day of the week and that was the supportive information I was using to back the original post that I referenced. </div></div>
You are correct; lag time is part of the actual time of flight.
However, when approximating wind drift, lag time is the only component used in the calculation. The total time of flight is not relevant.
Wind drift = crosswind speed x lag time.
It is a myth that wind deflection is caused by the wind blowing on the side of a bullet and pushing it off course (Litz, Applied Ballistics, page 84).
As to the trajectory data I presented, it was directed at the OP. I think that I clearly stated I was talking about the 155 scenar (the bullet Lowlight referenced) and not the 155 SMK. Also, I think it was clear that all the options I presented were better than the 175 SMK, including the 155 scenar.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K. </div></div>
Wind drift is determined by lag time, not time of flight. Lag time is the difference between the actual time of flight and the theoretical time of flight in a vacuum (distance/muzzle velocity).
Check out chapter 5 of Applied Ballistics by Bryan Litz. </div></div>
Lets just say that I am well aware of "true time of flight". I was not thinking in a vacuum!!!! Time of flight is the "total" time the projectile is exposed to the given conditions. The "lag-time", if you so wish to call it is simply part of the actual time of flight.
Also note, your g-7 data is not for the 155 smk and if you wish to use the g-7 data please use the new smk 2156c as it was the bullet I referenced. It's new BC is about 12% higher than the 2155.
If we are talking 155 smk vs. 175 smk the 155 wins to 1K any day of the week and that was the supportive information I was using to back the original post that I referenced. </div></div>
You are correct; lag time is part of the actual time of flight.
However, when approximating wind drift, lag time is the only component used in the calculation. The total time of flight is not relevant.
Wind drift = crosswind speed x lag time.
It is a myth that wind deflection is caused by the wind blowing on the side of a bullet and pushing it off course (Litz, Applied Ballistics, page 84).
As to the trajectory data I presented, it was directed at the OP. I think that I clearly stated I was talking about the 155 scenar (the bullet Lowlight referenced) and not the 155 SMK. Also, I think it was clear that all the options I presented were better than the 175 SMK, including the 155 scenar.
Re: 1/10 twist .308 to 1000yrds
I've tried the 168smk 155 palma 175smk and 180smk but none of the real heavy ones but to me the 168 AMAX is the way to go. I think it has the ones ive shot beat. But like i said ive never shot any thing heavier than 180 in a .308win. so 168 AMAX try it.
I've tried the 168smk 155 palma 175smk and 180smk but none of the real heavy ones but to me the 168 AMAX is the way to go. I think it has the ones ive shot beat. But like i said ive never shot any thing heavier than 180 in a .308win. so 168 AMAX try it.
Re: 1/10 twist .308 to 1000yrds
Lag time is a final representation of the outcome of the equations for the deceleration of a bullet caused by drag as controlled by ballistic co-efficient.
This is an adequate method of computing wind drift in a single wind variable system. In a multivariable wind scenario the lag time can be broken down into separate sections of seconds/(X)meters and multiplied by the wind value in that portion of the curve.
Example:
Lag(total 1km) = .14s
Lag1 (0m -333m) = .2s
Lag2 (333m-666m) = .4s
Lag3 (666m-1km) = .8s
Wind1 = 10m/s
Wind2 = 20m/s
Wind3 = 10m/s
Drift1 = 10m/s * .2s = 2m
Drift2 = 20m/s * .4s = 8m
Drift3 = 10m/s * .8s = 8m
Note that Lag(total) continues to increase per equal portion of time as an exponential curve.
Lag time is a final representation of the outcome of the equations for the deceleration of a bullet caused by drag as controlled by ballistic co-efficient.
This is an adequate method of computing wind drift in a single wind variable system. In a multivariable wind scenario the lag time can be broken down into separate sections of seconds/(X)meters and multiplied by the wind value in that portion of the curve.
Example:
Lag(total 1km) = .14s
Lag1 (0m -333m) = .2s
Lag2 (333m-666m) = .4s
Lag3 (666m-1km) = .8s
Wind1 = 10m/s
Wind2 = 20m/s
Wind3 = 10m/s
Drift1 = 10m/s * .2s = 2m
Drift2 = 20m/s * .4s = 8m
Drift3 = 10m/s * .8s = 8m
Note that Lag(total) continues to increase per equal portion of time as an exponential curve.
Re: 1/10 twist .308 to 1000yrds
looks good
looks good
Re: 1/10 twist .308 to 1000yrds
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K. </div></div>
Wind drift is determined by lag time, not time of flight. Lag time is the difference between the actual time of flight and the theoretical time of flight in a vacuum (distance/muzzle velocity).
Check out chapter 5 of Applied Ballistics by Bryan Litz. </div></div>
Lets just say that I am well aware of "true time of flight". I was not thinking in a vacuum!!!! Time of flight is the "total" time the projectile is exposed to the given conditions. The "lag-time", if you so wish to call it is simply part of the actual time of flight.
Also note, your g-7 data is not for the 155 smk and if you wish to use the g-7 data please use the new smk 2156c as it was the bullet I referenced. It's new BC is about 12% higher than the 2155.
If we are talking 155 smk vs. 175 smk the 155 wins to 1K any day of the week and that was the supportive information I was using to back the original post that I referenced. </div></div>
You are correct; lag time is part of the actual time of flight.
However, when approximating wind drift, lag time is the only component used in the calculation. The total time of flight is not relevant.
Wind drift = crosswind speed x lag time.
It is a myth that wind deflection is caused by the wind blowing on the side of a bullet and pushing it off course (Litz, Applied Ballistics, page 84).
As to the trajectory data I presented, it was directed at the OP. I think that I clearly stated I was talking about the 155 scenar (the bullet Lowlight referenced) and not the 155 SMK. Also, I think it was clear that all the options I presented were better than the 175 SMK, including the 155 scenar.
</div></div>
I am obviously learning something new here. I have been laboring under the assumption that bullet deflection was dependent on a vector (wind, gravity) imparting acceleration in the vector's direction; the amount of acceleration, hence displacement from the parabola of flight, was directly dependent on the time of the vector's action (acceleration= force X time). Hence, if two bullets are fired under identical conditions at identical velocities, the more aerodynamic projectile (higer B.C.) gets downrange more quickly, thus allowing less time for wind and gravity to impart wind drift and drop.
Up to this point, I believed the bullet to be susceptible to vectors as soon as it left the barrel until it reached the target, a period I have always termed "time of flight", or the actual time the bullet is in the air. The term "lag time" and its use in this discussion has me confused; if I read correctly, lag time is the difference between "ideal" flight time and actual flight time. I'm presuming lag time must be a relatively large number compared to "flight time", but I'm still stuck on the notion that a bullet is susceptible to gravity acceleration and wind deflection from muzzle to target, and I've always believed that to be called "flight time". A little help here?
Add: I understand that a low B.C. bullet that can be fired at a higher m.V. than a heavier high B.C. bullet can drop less and be less affected by wind and closer ranges owing to their higher initial M.V., but at some point downrange the low B.C. bullet begins to shed velocity faster than the slower, high B.C. bullet, thus beginning to lose it's initial advantage.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: runngun</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cmonroe</div><div class="ubbcode-body">Just my .02 worth, time in flight has just as much to do with wind as BC. I am back to shooting 155's at distance with the .308. I have a Savage 1-10 and a couple of Remington's with both 1-10 and 1-12 all I will add shoot the 155 SMK's very well and with a 100 zero I only need 8.6 mils to walk the K. </div></div>
Wind drift is determined by lag time, not time of flight. Lag time is the difference between the actual time of flight and the theoretical time of flight in a vacuum (distance/muzzle velocity).
Check out chapter 5 of Applied Ballistics by Bryan Litz. </div></div>
Lets just say that I am well aware of "true time of flight". I was not thinking in a vacuum!!!! Time of flight is the "total" time the projectile is exposed to the given conditions. The "lag-time", if you so wish to call it is simply part of the actual time of flight.
Also note, your g-7 data is not for the 155 smk and if you wish to use the g-7 data please use the new smk 2156c as it was the bullet I referenced. It's new BC is about 12% higher than the 2155.
If we are talking 155 smk vs. 175 smk the 155 wins to 1K any day of the week and that was the supportive information I was using to back the original post that I referenced. </div></div>
You are correct; lag time is part of the actual time of flight.
However, when approximating wind drift, lag time is the only component used in the calculation. The total time of flight is not relevant.
Wind drift = crosswind speed x lag time.
It is a myth that wind deflection is caused by the wind blowing on the side of a bullet and pushing it off course (Litz, Applied Ballistics, page 84).
As to the trajectory data I presented, it was directed at the OP. I think that I clearly stated I was talking about the 155 scenar (the bullet Lowlight referenced) and not the 155 SMK. Also, I think it was clear that all the options I presented were better than the 175 SMK, including the 155 scenar.
</div></div>
I am obviously learning something new here. I have been laboring under the assumption that bullet deflection was dependent on a vector (wind, gravity) imparting acceleration in the vector's direction; the amount of acceleration, hence displacement from the parabola of flight, was directly dependent on the time of the vector's action (acceleration= force X time). Hence, if two bullets are fired under identical conditions at identical velocities, the more aerodynamic projectile (higer B.C.) gets downrange more quickly, thus allowing less time for wind and gravity to impart wind drift and drop.
Up to this point, I believed the bullet to be susceptible to vectors as soon as it left the barrel until it reached the target, a period I have always termed "time of flight", or the actual time the bullet is in the air. The term "lag time" and its use in this discussion has me confused; if I read correctly, lag time is the difference between "ideal" flight time and actual flight time. I'm presuming lag time must be a relatively large number compared to "flight time", but I'm still stuck on the notion that a bullet is susceptible to gravity acceleration and wind deflection from muzzle to target, and I've always believed that to be called "flight time". A little help here?
Add: I understand that a low B.C. bullet that can be fired at a higher m.V. than a heavier high B.C. bullet can drop less and be less affected by wind and closer ranges owing to their higher initial M.V., but at some point downrange the low B.C. bullet begins to shed velocity faster than the slower, high B.C. bullet, thus beginning to lose it's initial advantage.
Shameless Plug
1ZNUF,
Lag time and the mechanics of wind deflection is Chapter 5 of: Applied Ballistics For Long Range Shooting
-Bryan
1ZNUF,
Lag time and the mechanics of wind deflection is Chapter 5 of: Applied Ballistics For Long Range Shooting
-Bryan
Re: Shameless Plug
Thanks, Bryan. I think I'm coming down with the flu; I'll hit Amazon for some reading material.
Thanks, Bryan. I think I'm coming down with the flu; I'll hit Amazon for some reading material.
