What experience do you have with longer bullets like the 139s or the 142s in the 1 in 9. I know some of the DPMS rifles were 1 in 9 with a 20" barrel, if you have velocity's that would be helpful.
- Thread starter Oakland Tactical
- Start date
Re: .260 with a 1 in 9
I'm building a .260 right now to shoot either 140 A-MAX or 142 SMK, but with a 1:8 twist Krieger. With a 26" barrel I'm expecting to get 2700-2900 fps depending on which powder ends up being the best. I know, different twist rates, but maybe this will help.
I'm building a .260 right now to shoot either 140 A-MAX or 142 SMK, but with a 1:8 twist Krieger. With a 26" barrel I'm expecting to get 2700-2900 fps depending on which powder ends up being the best. I know, different twist rates, but maybe this will help.
Re: .260 with a 1 in 9
if you have the option i would get a 1 in 8 twist if you want to shoot the 140gr bullets. I shoot the 140gr Berger VLD's out of a 24in Kreiger with a 1 in 8.
with 42.8gr of IMR 4350 they will go 2715fps.
with a 20in bbl i would guess you would be around 2400-2500fps
if your looking to shoot the high BC bullets at long range i would get a longer bbl, you'll kick yourself later if you dont.
if you have the option i would get a 1 in 8 twist if you want to shoot the 140gr bullets. I shoot the 140gr Berger VLD's out of a 24in Kreiger with a 1 in 8.
with 42.8gr of IMR 4350 they will go 2715fps.
with a 20in bbl i would guess you would be around 2400-2500fps
if your looking to shoot the high BC bullets at long range i would get a longer bbl, you'll kick yourself later if you dont.
Re: .260 with a 1 in 9
I just was wondering if it was like the difference between 1 in 7 and a 1 in 8 like the AR barrels. They can each shoot the 77-80 grain. I have already bought the 20 inch LMT barrel so I guess I will have to shoot the lighter bullets. I know a lot of people shoot the .260/8.5 twist with the heavy’s so I thought the 1/2 twist gain was not going to be that much of a difference. So much for assuming.
I just was wondering if it was like the difference between 1 in 7 and a 1 in 8 like the AR barrels. They can each shoot the 77-80 grain. I have already bought the 20 inch LMT barrel so I guess I will have to shoot the lighter bullets. I know a lot of people shoot the .260/8.5 twist with the heavy’s so I thought the 1/2 twist gain was not going to be that much of a difference. So much for assuming.
Re: .260 with a 1 in 9
1:8 is the key with a 260. That's what I have always shot (in both bolt and AR). 1:8.5 may work for some, but not all. 1:9 is not going to work well IMO.
1:8 is the key with a 260. That's what I have always shot (in both bolt and AR). 1:8.5 may work for some, but not all. 1:9 is not going to work well IMO.
Re: .260 with a 1 in 9
GAP sells there AR's with 1:8.5
GAP sells there AR's with 1:8.5
Re: .260 with a 1 in 9
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: fastford</div><div class="ubbcode-body">GAP sells there AR's with 1:8.5</div></div>
GAP will sell theirs with whatever twist you want. Plus, an AR is a different platform than an bolt. My AR happens to be a 1:8.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: fastford</div><div class="ubbcode-body">GAP sells there AR's with 1:8.5</div></div>
GAP will sell theirs with whatever twist you want. Plus, an AR is a different platform than an bolt. My AR happens to be a 1:8.
Re: .260 with a 1 in 9
i believe both my bolt and ar came from GAP in 8.5 i told them nothing more than give me the best ya got
i believe both my bolt and ar came from GAP in 8.5 i told them nothing more than give me the best ya got
Re: .260 with a 1 in 9
slower barrels are for the larger case capacity like the 6.5x284
10 twist would prolly be perfect as this particular bullet will be a blowtorch anyway
slower barrels are for the larger case capacity like the 6.5x284
10 twist would prolly be perfect as this particular bullet will be a blowtorch anyway
Re: .260 with a 1 in 9
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: fastford</div><div class="ubbcode-body">i believe both my bolt and ar came from GAP in 8.5 i told them nothing more than give me the best ya got</div></div>
and they thought "or give you what we have in stock." Either way, whatever works for the OP.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: fastford</div><div class="ubbcode-body">i believe both my bolt and ar came from GAP in 8.5 i told them nothing more than give me the best ya got</div></div>
and they thought "or give you what we have in stock." Either way, whatever works for the OP.
Re: .260 with a 1 in 9
I read a good quote by Boots Obermeyer on here a little while ago that caused me to go with a 8.75 twist.
Boots is a big 6.5 buy and seems to be of the mindset that the 8" twist is over stabilizing the 140 class bullets. and that it is really meant for the heavier guys.
Lemme see if I can find it.
I read a good quote by Boots Obermeyer on here a little while ago that caused me to go with a 8.75 twist.
Boots is a big 6.5 buy and seems to be of the mindset that the 8" twist is over stabilizing the 140 class bullets. and that it is really meant for the heavier guys.
Lemme see if I can find it.
Re: .260 with a 1 in 9
gots it!
from here:
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2326136#Post2326136
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SDWhirlwind</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mmay190030</div><div class="ubbcode-body">Looking for an 8 twist, 6.5 mm </div></div>
Hope Bugholes doesn't mind my posting but seeing as it concerns Obermeyer barrels. Boots and I had a couple phone conversations and then I had emailed him my order, below is a cut/paste from Boots in Aug of 07 concerning twist and 6.5 barrels that him and I had in an email exchange. I am running a 28" 9.1tw Oby on my 6.5x47L but only shooting 123L @ 3015fps. This as a FYI....
------------------------------------------------------------------------
Dennis
The 8 twist is too fast for 6.5's using 140-142 bullets for long range. I have shot 142's down to 2600 Ft/sec with a 260 using an 8-3/4 twist and got cleans at 600. If you go real fast you keep the nose up more as it rolls over the peak of trajectory which increases the nose turbulence. Also the faster the twist the harder it is on the bullet jacket causing more fouling or failures. I normally shoot 140 range bullets at about 2725. You can go faster but the sweet point is 2725-2750 max.
I have a 6.5 x 22-250 that I shoot 140 Hornadys at 2715. I shot 7 cleans in a row at 600 with it and this 8-3/4 twist barrel has shot 3 200-19X at 600.
My 308's are 11 twist, actually a hair faster. Remington was 11-1/4. The differences are simply small differences in gearing. The Remington is a hammer forged barrel. Life is a lot less.
What length on the .308?
Boots
-- ------------------------------------------------------------------
YMMV.....,however, I figured him shooting several 6.5's in competitions and being one of the best barrel makers might be good advice and considerably more than I 'think' I know or read on the net.
Respectfully,
Dennis </div></div>
gots it!
from here:
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2326136#Post2326136
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SDWhirlwind</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mmay190030</div><div class="ubbcode-body">Looking for an 8 twist, 6.5 mm </div></div>
Hope Bugholes doesn't mind my posting but seeing as it concerns Obermeyer barrels. Boots and I had a couple phone conversations and then I had emailed him my order, below is a cut/paste from Boots in Aug of 07 concerning twist and 6.5 barrels that him and I had in an email exchange. I am running a 28" 9.1tw Oby on my 6.5x47L but only shooting 123L @ 3015fps. This as a FYI....
------------------------------------------------------------------------
Dennis
The 8 twist is too fast for 6.5's using 140-142 bullets for long range. I have shot 142's down to 2600 Ft/sec with a 260 using an 8-3/4 twist and got cleans at 600. If you go real fast you keep the nose up more as it rolls over the peak of trajectory which increases the nose turbulence. Also the faster the twist the harder it is on the bullet jacket causing more fouling or failures. I normally shoot 140 range bullets at about 2725. You can go faster but the sweet point is 2725-2750 max.
I have a 6.5 x 22-250 that I shoot 140 Hornadys at 2715. I shot 7 cleans in a row at 600 with it and this 8-3/4 twist barrel has shot 3 200-19X at 600.
My 308's are 11 twist, actually a hair faster. Remington was 11-1/4. The differences are simply small differences in gearing. The Remington is a hammer forged barrel. Life is a lot less.
What length on the .308?
Boots
-- ------------------------------------------------------------------
YMMV.....,however, I figured him shooting several 6.5's in competitions and being one of the best barrel makers might be good advice and considerably more than I 'think' I know or read on the net.
Respectfully,
Dennis </div></div>
Re: .260 with a 1 in 9
Technically, a 140 grain SHOULD stabilize out of a 1:9". But you will need to push it fast to make sure. I don't know you can get it fast enough out of a 20". It's a gamble to know for sure. I run an 8.5" twist in my 260.
Technically, a 140 grain SHOULD stabilize out of a 1:9". But you will need to push it fast to make sure. I don't know you can get it fast enough out of a 20". It's a gamble to know for sure. I run an 8.5" twist in my 260.
Re: .260 with a 1 in 9
Looking at the NF Ballistic program is there any real .260 advantage over the 308 with the 20" barrel? my program shows only a 6.25 MOA elevation advantage and a 2.25 MOA windage advantage at 1000.
This is comparing a 175 SMK at 2500 (16"barrel) and a 140 Amax Scenar at 2550 (20" barrel) I thought you could push the 140s around 2650-2700 out of the 20" being guys are pushing them much faster out of longer barrels.
Looking at the NF Ballistic program is there any real .260 advantage over the 308 with the 20" barrel? my program shows only a 6.25 MOA elevation advantage and a 2.25 MOA windage advantage at 1000.
This is comparing a 175 SMK at 2500 (16"barrel) and a 140 Amax Scenar at 2550 (20" barrel) I thought you could push the 140s around 2650-2700 out of the 20" being guys are pushing them much faster out of longer barrels.
Re: .260 with a 1 in 9
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Re25</div><div class="ubbcode-body">Looking at the NF Ballistic program is there any real .260 advantage over the 308 with the 20" barrel? my program shows only a 6.25 MOA elevation advantage and a 2.25 MOA windage advantage at 1000.
This is comparing a 175 SMK at 2500 (16"barrel) and a 140 Amax Scenar at 2550 (20" barrel) I thought you could push the 140s around 2650-2700 out of the 20" being guys are pushing them much faster out of longer barrels. </div></div>
I would look at the windage and velocity at 1K my ballistics program shows a 139 scenar moving at about 1500 fps while the 168 SMK is barely holding supersonic flight at 1159. Also the .260 has about 40 inches less wind drift at 1K from a 10mph full value wind.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Re25</div><div class="ubbcode-body">Looking at the NF Ballistic program is there any real .260 advantage over the 308 with the 20" barrel? my program shows only a 6.25 MOA elevation advantage and a 2.25 MOA windage advantage at 1000.
This is comparing a 175 SMK at 2500 (16"barrel) and a 140 Amax Scenar at 2550 (20" barrel) I thought you could push the 140s around 2650-2700 out of the 20" being guys are pushing them much faster out of longer barrels. </div></div>
I would look at the windage and velocity at 1K my ballistics program shows a 139 scenar moving at about 1500 fps while the 168 SMK is barely holding supersonic flight at 1159. Also the .260 has about 40 inches less wind drift at 1K from a 10mph full value wind.
Re: .260 with a 1 in 9
If you look at my post in the thread link below on April 9, 2010, it will give you some velocities for an 18" 260. You should be able to run them about 2670 to 2700. I got pressure with anything over 2700 fps. You're velocities are a little low for the 260. In a nut shell, the 260 is much more ballistically superior to a 308 with just about every bullet (for punching paper and steel). You do loose the heavier projectile for killin chit, though.
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1395546&page=7
If you look at my post in the thread link below on April 9, 2010, it will give you some velocities for an 18" 260. You should be able to run them about 2670 to 2700. I got pressure with anything over 2700 fps. You're velocities are a little low for the 260. In a nut shell, the 260 is much more ballistically superior to a 308 with just about every bullet (for punching paper and steel). You do loose the heavier projectile for killin chit, though.
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1395546&page=7
Re: .260 with a 1 in 9
Chad,
wht kind of velocity do you think could be obtained with a 20" 260 AR?
Chad,
wht kind of velocity do you think could be obtained with a 20" 260 AR?
Re: .260 with a 1 in 9
I guess some say the 1 in 9 will work and some say it wont. Same for the 20" barrel. I guess I'll have to test it and see.
I guess some say the 1 in 9 will work and some say it wont. Same for the 20" barrel. I guess I'll have to test it and see.
Re: .260 with a 1 in 9
tag
tag
Re: .260 with a 1 in 9
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: fastford</div><div class="ubbcode-body">Chad,
wht kind of velocity do you think could be obtained with a 20" 260 AR? </div></div>
For a 140, probably 2650 to 2700ish. If I were to run a short gas gun, I'd run a 120 or 130 class bullet. This way you can get your speeds up some, and still have decent BC. Or just run the 140's slower with more drop, and get less wind drift. Either way it's a compromise, and you have to pick what best suites your needs.
I am switching over to a 130 grain VLD for my 260 right now. It's shooting awesome (1.1" at 415 yards), but I'm getting pressure with this load.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: fastford</div><div class="ubbcode-body">Chad,
wht kind of velocity do you think could be obtained with a 20" 260 AR? </div></div>
For a 140, probably 2650 to 2700ish. If I were to run a short gas gun, I'd run a 120 or 130 class bullet. This way you can get your speeds up some, and still have decent BC. Or just run the 140's slower with more drop, and get less wind drift. Either way it's a compromise, and you have to pick what best suites your needs.
I am switching over to a 130 grain VLD for my 260 right now. It's shooting awesome (1.1" at 415 yards), but I'm getting pressure with this load.
