So for the loaders with experience, has this powder lived up to all the hype since its release about a year ago? How does it compare to Varget? Burn time too fast for heavier bullets like, say 175 gr in .308? Does it meter like a ball powder?
IMR 8208 XBR, thumbs up?
- Thread starter schwim
- Start date
Re: IMR 8208 XBR, thumbs up?
I use it in a 270 Winchester with excellent results with 130 gr. bullets.
It meters better than any other powder I've used including ball powders. I generally weigh all charges but after throwing dozens of charges and finding the thrown weight to be right on, I quit weighing individual charges with that powder.
I have tried it in a 30/06 with 150 gr. bullets and in a 204 Ruger with 45 gr. bullets and it didn't do as well accuracy wise as with some other powders so it's obviously not the cure all for everything.
I use it in a 270 Winchester with excellent results with 130 gr. bullets.
It meters better than any other powder I've used including ball powders. I generally weigh all charges but after throwing dozens of charges and finding the thrown weight to be right on, I quit weighing individual charges with that powder.
I have tried it in a 30/06 with 150 gr. bullets and in a 204 Ruger with 45 gr. bullets and it didn't do as well accuracy wise as with some other powders so it's obviously not the cure all for everything.
Re: IMR 8208 XBR, thumbs up?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: hyoslvr</div><div class="ubbcode-body">Yep I used to use varget in my .308 bolt but since they have released xbr its now my go to powder. Very consistant powder. </div></div>
Sounds promising, what bullet(s) are you launching? In the few posts I've seen, there seemed to be great results with lighter pills but questionable results with heavier.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: hyoslvr</div><div class="ubbcode-body">Yep I used to use varget in my .308 bolt but since they have released xbr its now my go to powder. Very consistant powder. </div></div>
Sounds promising, what bullet(s) are you launching? In the few posts I've seen, there seemed to be great results with lighter pills but questionable results with heavier.
Re: IMR 8208 XBR, thumbs up?
is this "new" IMR 8208 XBR have any resemblance to the old military 8208 ? i have about 12 lbs. of it, kinda dirty, and has a strong odor that i can not describe when fired, but has good performance in a .223 Rem./5.56mm NATO when fired from a piston rifle/carbine, with gas impingement it will dirty up a gun pretty fast.
is this "new" IMR 8208 XBR have any resemblance to the old military 8208 ? i have about 12 lbs. of it, kinda dirty, and has a strong odor that i can not describe when fired, but has good performance in a .223 Rem./5.56mm NATO when fired from a piston rifle/carbine, with gas impingement it will dirty up a gun pretty fast.
Re: IMR 8208 XBR, thumbs up?
Don't know about resemblance to the old, but it is a new product being imported from Australia with a similar name but no other relation as I understand it.
Did u get yours new from a dealer recently, and is it labeled as in the post title? Some of the old can still be had, but It's pretty rare and hence pricey, I believe.
Don't know about resemblance to the old, but it is a new product being imported from Australia with a similar name but no other relation as I understand it.
Did u get yours new from a dealer recently, and is it labeled as in the post title? Some of the old can still be had, but It's pretty rare and hence pricey, I believe.
Re: IMR 8208 XBR, thumbs up?
I have been working up loads for for several calibers but I am not to the point of being able to make a judgement on accuracy yet. However on metering in my Dillon 550b, it is better than 4895 but I still get easy +/- .3gr variations. So not the best in the 550b.
I have been working up loads for for several calibers but I am not to the point of being able to make a judgement on accuracy yet. However on metering in my Dillon 550b, it is better than 4895 but I still get easy +/- .3gr variations. So not the best in the 550b.
Re: IMR 8208 XBR, thumbs up?
I load it in my FIL's 700 SPS Varmint in .223. It shoots better than Benchmark, N133, H4198, TAC, N530 in his rifle. My OCW load of 24.3g with the 52g Amax shoots bugholes all day long. I have found accuracy to be similar at 85 degrees where load development was done and at 25 degrees where we shot it recently. It also burns very cleanly in his rifle. It has replaced N133 as my go-to powder for 52-55g bullets in his .223.
I load it in my FIL's 700 SPS Varmint in .223. It shoots better than Benchmark, N133, H4198, TAC, N530 in his rifle. My OCW load of 24.3g with the 52g Amax shoots bugholes all day long. I have found accuracy to be similar at 85 degrees where load development was done and at 25 degrees where we shot it recently. It also burns very cleanly in his rifle. It has replaced N133 as my go-to powder for 52-55g bullets in his .223.
Re: IMR 8208 XBR, thumbs up?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Piston Pete</div><div class="ubbcode-body">is this "new" IMR 8208 XBR have any resemblance to the old military 8208 ? i have about 12 lbs. of it, kinda dirty, and has a strong odor that i can not describe when fired, but has good performance in a .223 Rem./5.56mm NATO when fired from a piston rifle/carbine, with gas impingement it will dirty up a gun pretty fast. </div></div>
It's probably the cleanest powder I use.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Piston Pete</div><div class="ubbcode-body">is this "new" IMR 8208 XBR have any resemblance to the old military 8208 ? i have about 12 lbs. of it, kinda dirty, and has a strong odor that i can not describe when fired, but has good performance in a .223 Rem./5.56mm NATO when fired from a piston rifle/carbine, with gas impingement it will dirty up a gun pretty fast. </div></div>
It's probably the cleanest powder I use.
Re: IMR 8208 XBR, thumbs up?
so fare its been shooting great out of my rifel.its a 5R chambered in a 223 with a 1"9 twist.I am useing lapua brass 69gn NCC bullet and 450 CCI primers.my charge weight is 24.5gn's and the bullet is just touching the lands with a C.O.A.L. of 2.290.
at 100 the load shot a .200 something group 5 shoots.the first time out at 300 it gave me a 15 shot group that a quarter just could cover up.but will say that I have yet been able to reshoot that group again.the weather and wind around here has been a huge pain in the butt.but the load will shoot a nice 2 inch or less all day at 300 yards.
and yes I too say its a clean powder.and will add that I will be soon getting an 8# jug of it along with 1000 69gn NCC bullets.then me and the wife can have all the fun we want for some time or till the bullets/powder runs out.LOLso yes I.the rifel likes this powder.and it the got to powder for this one rifel.
so fare its been shooting great out of my rifel.its a 5R chambered in a 223 with a 1"9 twist.I am useing lapua brass 69gn NCC bullet and 450 CCI primers.my charge weight is 24.5gn's and the bullet is just touching the lands with a C.O.A.L. of 2.290.
at 100 the load shot a .200 something group 5 shoots.the first time out at 300 it gave me a 15 shot group that a quarter just could cover up.but will say that I have yet been able to reshoot that group again.the weather and wind around here has been a huge pain in the butt.but the load will shoot a nice 2 inch or less all day at 300 yards.
and yes I too say its a clean powder.and will add that I will be soon getting an 8# jug of it along with 1000 69gn NCC bullets.then me and the wife can have all the fun we want for some time or till the bullets/powder runs out.LOLso yes I.the rifel likes this powder.and it the got to powder for this one rifel.
Re: IMR 8208 XBR, thumbs up?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ed-G</div><div class="ubbcode-body">I have been working up loads for for several calibers but I am not to the point of being able to make a judgement on accuracy yet. However on metering in my Dillon 550b, it is better than 4895 but I still get easy +/- .3gr variations. So not the best in the 550b.
</div></div>
Did you try the polish trick on your funnel?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ed-G</div><div class="ubbcode-body">I have been working up loads for for several calibers but I am not to the point of being able to make a judgement on accuracy yet. However on metering in my Dillon 550b, it is better than 4895 but I still get easy +/- .3gr variations. So not the best in the 550b.
</div></div>
Did you try the polish trick on your funnel?
Re: IMR 8208 XBR, thumbs up?
Schwim, i got mine from a friend who had connections to another person whom i never saw, i gave my container to my friend empty and he returned it full, i handed him a $100 bill and went home, the guy bought "several barrels full", i have no idea and never asked how big/heavy a "barrel" was, all i know about it was that is was military surplus, this was about 8 years ago he was selling it at $10.00 a lb., i supplied my own container, an old 10 lb. powder canister, he filled it to the brim, curious, i weighed out the powder, i got just a little over 12 lb., a week later, i got another canister full, it weighed 12.6 lb., i done this 3 more times, my powder magazine was getting crowded, i have not seen or heard from my friend in two years, i lost his phone number and he moved to a different area of town.
Schwim, i got mine from a friend who had connections to another person whom i never saw, i gave my container to my friend empty and he returned it full, i handed him a $100 bill and went home, the guy bought "several barrels full", i have no idea and never asked how big/heavy a "barrel" was, all i know about it was that is was military surplus, this was about 8 years ago he was selling it at $10.00 a lb., i supplied my own container, an old 10 lb. powder canister, he filled it to the brim, curious, i weighed out the powder, i got just a little over 12 lb., a week later, i got another canister full, it weighed 12.6 lb., i done this 3 more times, my powder magazine was getting crowded, i have not seen or heard from my friend in two years, i lost his phone number and he moved to a different area of town.
Re: IMR 8208 XBR, thumbs up?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Piston Pete</div><div class="ubbcode-body">Schwim, i got mine from a friend who had connections to another person whom i never saw, i gave my container to my friend empty and he returned it full, i handed him a $100 bill and went home, the guy bought "several barrels full", i have no idea and never asked how big/heavy a "barrel" was, all i know about it was that is was military surplus, this was about 8 years ago he was selling it at $10.00 a lb., i supplied my own container, an old 10 lb. powder canister, he filled it to the brim, curious, i weighed out the powder, i got just a little over 12 lb., a week later, i got another canister full, it weighed 12.6 lb., i done this 3 more times, my powder magazine was getting crowded, i have not seen or heard from my friend in two years, i lost his phone number and he moved to a different area of town. </div></div>
Sounds like you got the original, good score!
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Piston Pete</div><div class="ubbcode-body">Schwim, i got mine from a friend who had connections to another person whom i never saw, i gave my container to my friend empty and he returned it full, i handed him a $100 bill and went home, the guy bought "several barrels full", i have no idea and never asked how big/heavy a "barrel" was, all i know about it was that is was military surplus, this was about 8 years ago he was selling it at $10.00 a lb., i supplied my own container, an old 10 lb. powder canister, he filled it to the brim, curious, i weighed out the powder, i got just a little over 12 lb., a week later, i got another canister full, it weighed 12.6 lb., i done this 3 more times, my powder magazine was getting crowded, i have not seen or heard from my friend in two years, i lost his phone number and he moved to a different area of town. </div></div>
Sounds like you got the original, good score!
Re: IMR 8208 XBR, thumbs up?
I did but I did a half ass job compared to some pictures of other guys work that I looked up this AM. I need to redue and then re-evaluate. Hopefully I can get down to +/-0.1gr that some are reporting.
I did but I did a half ass job compared to some pictures of other guys work that I looked up this AM. I need to redue and then re-evaluate. Hopefully I can get down to +/-0.1gr that some are reporting.
Re: IMR 8208 XBR, thumbs up?
Glad I found this thread, I was about to post the same Q? So can someone explain to me the pressures and velocity, on Hogdon's website it states that for a 168 gr 308 BTHP the max load is 43.3 grains the pressure is 61,500 & the velocity is 2707...
So I guess that the pressure does not determine the velocity, how come? Thanks
Glad I found this thread, I was about to post the same Q? So can someone explain to me the pressures and velocity, on Hogdon's website it states that for a 168 gr 308 BTHP the max load is 43.3 grains the pressure is 61,500 & the velocity is 2707...
So I guess that the pressure does not determine the velocity, how come? Thanks
Re: IMR 8208 XBR, thumbs up?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308saiga</div><div class="ubbcode-body">Glad I found this thread, I was about to post the same Q? So can someone explain to me the pressures and velocity, on Hogdon's website it states that for a 168 gr 308 BTHP the max load is 43.3 grains the pressure is 61,500 & the velocity is 2707...
So I guess that the pressure does not determine the velocity, how come? Thanks </div></div>
I'm interested too, probably has something to do with burn rate? Is there any other variable that would account for this?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308saiga</div><div class="ubbcode-body">Glad I found this thread, I was about to post the same Q? So can someone explain to me the pressures and velocity, on Hogdon's website it states that for a 168 gr 308 BTHP the max load is 43.3 grains the pressure is 61,500 & the velocity is 2707...
So I guess that the pressure does not determine the velocity, how come? Thanks </div></div>
I'm interested too, probably has something to do with burn rate? Is there any other variable that would account for this?
Re: IMR 8208 XBR, thumbs up?
In my custom chamber I have found 8208 to be great with 155-168grain bullets. With 175's I am about 50 fps slower than varget before reaching pressure signs. So I save the varget for 175's and use 8208 for everything lighter.
Group wise, 8208 may be slightly better than varget but its so close I wouldnt put money on it. It does meter better.
In my custom chamber I have found 8208 to be great with 155-168grain bullets. With 175's I am about 50 fps slower than varget before reaching pressure signs. So I save the varget for 175's and use 8208 for everything lighter.
Group wise, 8208 may be slightly better than varget but its so close I wouldnt put money on it. It does meter better.
Re: IMR 8208 XBR, thumbs up?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Piston Pete</div><div class="ubbcode-body">is this "new" IMR 8208 XBR have any resemblance to the old military 8208 ? i have about 12 lbs. of it, kinda dirty, and has a strong odor that i can not describe when fired, but has good performance in a .223 Rem./5.56mm NATO when fired from a piston rifle/carbine, with gas impingement it will dirty up a gun pretty fast.</div></div>
it did not shoot worth a darn in my POF .223, i still like bl(c)-2
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Piston Pete</div><div class="ubbcode-body">is this "new" IMR 8208 XBR have any resemblance to the old military 8208 ? i have about 12 lbs. of it, kinda dirty, and has a strong odor that i can not describe when fired, but has good performance in a .223 Rem./5.56mm NATO when fired from a piston rifle/carbine, with gas impingement it will dirty up a gun pretty fast.</div></div>
it did not shoot worth a darn in my POF .223, i still like bl(c)-2
Re: IMR 8208 XBR, thumbs up?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308saiga</div><div class="ubbcode-body">Glad I found this thread, I was about to post the same Q? So can someone explain to me the pressures and velocity, on Hogdon's website it states that for a 168 gr 308 BTHP the max load is 43.3 grains the pressure is 61,500 & the velocity is 2707...
So I guess that the pressure does not determine the velocity, how come? Thanks </div></div>
The bullet is being accelerated down the barrel by the expanding gasses behind it. The longer these gasses act on it the faster it goes. This is one reason a longer barrel yields higher velocities than a shorter barrel no matter what powder is used. But, as the bullet accelerates down the barrel, the room available for expansion increases and pressure begins to decrease. This causes the rate of acceleration to slow down. Its still accelerating the bullet but the rate of acceleration is dropping off. The burn rate of the powder will determine how much acceleration is imparted to the bullet. Some powders that reach a high pressure quickly have less pressure available to fill the expanding combustion area as the bullet travels down the bore. A powder that has a slower burn rate probably wont reach as high pressure as a fast powder but it maintains more pressure as the bullet moves down the bore. This is why powders with a slow or medium burn rate (Varget) achieve higher bullet velocity than a powder with a fast burn rate (Benchmark or , 8208 XBR). The slower powders maintain more pressure longer than the fast powders.
If you could calculate the area underneath the graph of a pressure curve for a bullet's trip down the barrel for a given powder, the curve with the greatest area would also have the highest muzzle velocity. Even though this curve may not have the highest pressure.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308saiga</div><div class="ubbcode-body">Glad I found this thread, I was about to post the same Q? So can someone explain to me the pressures and velocity, on Hogdon's website it states that for a 168 gr 308 BTHP the max load is 43.3 grains the pressure is 61,500 & the velocity is 2707...
So I guess that the pressure does not determine the velocity, how come? Thanks </div></div>
The bullet is being accelerated down the barrel by the expanding gasses behind it. The longer these gasses act on it the faster it goes. This is one reason a longer barrel yields higher velocities than a shorter barrel no matter what powder is used. But, as the bullet accelerates down the barrel, the room available for expansion increases and pressure begins to decrease. This causes the rate of acceleration to slow down. Its still accelerating the bullet but the rate of acceleration is dropping off. The burn rate of the powder will determine how much acceleration is imparted to the bullet. Some powders that reach a high pressure quickly have less pressure available to fill the expanding combustion area as the bullet travels down the bore. A powder that has a slower burn rate probably wont reach as high pressure as a fast powder but it maintains more pressure as the bullet moves down the bore. This is why powders with a slow or medium burn rate (Varget) achieve higher bullet velocity than a powder with a fast burn rate (Benchmark or , 8208 XBR). The slower powders maintain more pressure longer than the fast powders.
If you could calculate the area underneath the graph of a pressure curve for a bullet's trip down the barrel for a given powder, the curve with the greatest area would also have the highest muzzle velocity. Even though this curve may not have the highest pressure.
Re: IMR 8208 XBR, thumbs up?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jumper</div><div class="ubbcode-body">
The bullet is being accelerated down the barrel by the expanding gasses behind it. The longer these gasses act on it the faster it goes. This is one reason a longer barrel yields higher velocities than a shorter barrel no matter what powder is used. But, as the bullet accelerates down the barrel, the room available for expansion increases and pressure begins to decrease. This causes the rate of acceleration to slow down. Its still accelerating the bullet but the rate of acceleration is dropping off. The burn rate of the powder will determine how much acceleration is imparted to the bullet. Some powders that reach a high pressure quickly have less pressure available to fill the expanding combustion area as the bullet travels down the bore. A powder that has a slower burn rate probably wont reach as high pressure as a fast powder but it maintains more pressure as the bullet moves down the bore. This is why powders with a slow or medium burn rate (Varget) achieve higher bullet velocity than a powder with a fast burn rate (Benchmark or , 8208 XBR). The slower powders maintain more pressure longer than the fast powders.
If you could calculate the area underneath the graph of a pressure curve for a bullet's trip down the barrel for a given powder, the curve with the greatest area would also have the highest muzzle velocity. Even though this curve may not have the highest pressure. </div></div>
Thank you, so you may have already explained this, and if so I guess I did not understand the explanation and for that I apologize, but how are the pressures determined or measured?
Thanks again.....
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jumper</div><div class="ubbcode-body">
The bullet is being accelerated down the barrel by the expanding gasses behind it. The longer these gasses act on it the faster it goes. This is one reason a longer barrel yields higher velocities than a shorter barrel no matter what powder is used. But, as the bullet accelerates down the barrel, the room available for expansion increases and pressure begins to decrease. This causes the rate of acceleration to slow down. Its still accelerating the bullet but the rate of acceleration is dropping off. The burn rate of the powder will determine how much acceleration is imparted to the bullet. Some powders that reach a high pressure quickly have less pressure available to fill the expanding combustion area as the bullet travels down the bore. A powder that has a slower burn rate probably wont reach as high pressure as a fast powder but it maintains more pressure as the bullet moves down the bore. This is why powders with a slow or medium burn rate (Varget) achieve higher bullet velocity than a powder with a fast burn rate (Benchmark or , 8208 XBR). The slower powders maintain more pressure longer than the fast powders.
If you could calculate the area underneath the graph of a pressure curve for a bullet's trip down the barrel for a given powder, the curve with the greatest area would also have the highest muzzle velocity. Even though this curve may not have the highest pressure. </div></div>
Thank you, so you may have already explained this, and if so I guess I did not understand the explanation and for that I apologize, but how are the pressures determined or measured?
Thanks again.....
Re: IMR 8208 XBR, thumbs up?
The powder companies and the ammo companies have barrels with pressure measuring sensors built in. They test fire their rounds and measure the expansion of the barrel with a piezo-electric sensor. The old method used to be how much it crushed a copper cylinder that was affixed to the barrel. In load manuals these units are listed as CUP - copper units of Pressure. The modern way is in PSI with the piezo electric sensor.
The powder companies and the ammo companies have barrels with pressure measuring sensors built in. They test fire their rounds and measure the expansion of the barrel with a piezo-electric sensor. The old method used to be how much it crushed a copper cylinder that was affixed to the barrel. In load manuals these units are listed as CUP - copper units of Pressure. The modern way is in PSI with the piezo electric sensor.
Re: IMR 8208 XBR, thumbs up?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jumper</div><div class="ubbcode-body">The powder companies and the ammo companies have barrels with pressure measuring sensors built in. They test fire their rounds and measure the expansion of the barrel with a piezo-electric sensor. The old method used to be how much it crushed a copper cylinder that was affixed to the barrel. In load manuals these units are listed as CUP - copper units of Pressure. The modern way is in PSI with the piezo electric sensor. </div></div>
Awesome, thank you......
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jumper</div><div class="ubbcode-body">The powder companies and the ammo companies have barrels with pressure measuring sensors built in. They test fire their rounds and measure the expansion of the barrel with a piezo-electric sensor. The old method used to be how much it crushed a copper cylinder that was affixed to the barrel. In load manuals these units are listed as CUP - copper units of Pressure. The modern way is in PSI with the piezo electric sensor. </div></div>
Awesome, thank you......
Re: IMR 8208 XBR, thumbs up?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jumper</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308saiga</div><div class="ubbcode-body">Glad I found this thread, I was about to post the same Q? So can someone explain to me the pressures and velocity, on Hogdon's website it states that for a 168 gr 308 BTHP the max load is 43.3 grains the pressure is 61,500 & the velocity is 2707...
So I guess that the pressure does not determine the velocity, how come? Thanks </div></div>
The bullet is being accelerated down the barrel by the expanding gasses behind it. The longer these gasses act on it the faster it goes. This is one reason a longer barrel yields higher velocities than a shorter barrel no matter what powder is used. But, as the bullet accelerates down the barrel, the room available for expansion increases and pressure begins to decrease. This causes the rate of acceleration to slow down. Its still accelerating the bullet but the rate of acceleration is dropping off. The burn rate of the powder will determine how much acceleration is imparted to the bullet. Some powders that reach a high pressure quickly have less pressure available to fill the expanding combustion area as the bullet travels down the bore. A powder that has a slower burn rate probably wont reach as high pressure as a fast powder but it maintains more pressure as the bullet moves down the bore. This is why powders with a slow or medium burn rate (Varget) achieve higher bullet velocity than a powder with a fast burn rate (Benchmark or , 8208 XBR). The slower powders maintain more pressure longer than the fast powders.
If you could calculate the area underneath the graph of a pressure curve for a bullet's trip down the barrel for a given powder, the curve with the greatest area would also have the highest muzzle velocity. Even though this curve may not have the highest pressure. </div></div>
Jump, thank you for explaining this
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jumper</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 308saiga</div><div class="ubbcode-body">Glad I found this thread, I was about to post the same Q? So can someone explain to me the pressures and velocity, on Hogdon's website it states that for a 168 gr 308 BTHP the max load is 43.3 grains the pressure is 61,500 & the velocity is 2707...
So I guess that the pressure does not determine the velocity, how come? Thanks </div></div>
The bullet is being accelerated down the barrel by the expanding gasses behind it. The longer these gasses act on it the faster it goes. This is one reason a longer barrel yields higher velocities than a shorter barrel no matter what powder is used. But, as the bullet accelerates down the barrel, the room available for expansion increases and pressure begins to decrease. This causes the rate of acceleration to slow down. Its still accelerating the bullet but the rate of acceleration is dropping off. The burn rate of the powder will determine how much acceleration is imparted to the bullet. Some powders that reach a high pressure quickly have less pressure available to fill the expanding combustion area as the bullet travels down the bore. A powder that has a slower burn rate probably wont reach as high pressure as a fast powder but it maintains more pressure as the bullet moves down the bore. This is why powders with a slow or medium burn rate (Varget) achieve higher bullet velocity than a powder with a fast burn rate (Benchmark or , 8208 XBR). The slower powders maintain more pressure longer than the fast powders.
If you could calculate the area underneath the graph of a pressure curve for a bullet's trip down the barrel for a given powder, the curve with the greatest area would also have the highest muzzle velocity. Even though this curve may not have the highest pressure. </div></div>
Jump, thank you for explaining this
Re: IMR 8208 XBR, thumbs up?
I like it alot, 168 a-max, and 175 matchking both shoot well. I'm also using it in my 6.5x55 with a 100gr BT to get 3300fps.
I like it alot, 168 a-max, and 175 matchking both shoot well. I'm also using it in my 6.5x55 with a 100gr BT to get 3300fps.
Re: IMR 8208 XBR, thumbs up?
Shot it today out of my AI AE 24" worked up to 46gr. Cold bore @ 45gr 2904 #2 2909 45.5gr #1 2937 #2 2940 46gr#1 2975 #2 2978 .155 scenar jammed about .003-.005 46gr had slight primer extrusion to be expected with an AI,bolt lift was perfect.all with br2's.conditions 51degrees 52% r/h 30.30 baro @aprox. 320ft ASL.I shot 46gr of varget the day before with all the same conditions and brass they were running 2780 average.@200 the 46gr load shot 3/8 moa.this is 1 gr. Above max be careful and work your rifle up.JUST SAYING.
Shot it today out of my AI AE 24" worked up to 46gr. Cold bore @ 45gr 2904 #2 2909 45.5gr #1 2937 #2 2940 46gr#1 2975 #2 2978 .155 scenar jammed about .003-.005 46gr had slight primer extrusion to be expected with an AI,bolt lift was perfect.all with br2's.conditions 51degrees 52% r/h 30.30 baro @aprox. 320ft ASL.I shot 46gr of varget the day before with all the same conditions and brass they were running 2780 average.@200 the 46gr load shot 3/8 moa.this is 1 gr. Above max be careful and work your rifle up.JUST SAYING.
Re: IMR 8208 XBR, thumbs up?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MedicGordo</div><div class="ubbcode-body">Shot it today out of my AI AE 24" worked up to 46gr. Cold bore @ 45gr 2904 #2 2909 45.5gr #1 2937 #2 2940 46gr#1 2975 #2 2978 .155 scenar jammed about .003-.005 46gr had slight primer extrusion to be expected with an AI,bolt lift was perfect.all with br2's.conditions 51degrees 52% r/h 30.30 baro @aprox. 320ft ASL.I shot 46gr of varget the day before with all the same conditions and brass they were running 2780 average.@200 the 46gr load shot 3/8 moa.this is 1 gr. Above max be careful and work your rifle up.JUST SAYING. </div></div>
Have you worked up any loads warmer than 46grains? I worked up to 46 grains today, but was wondering if I could take it much farther. I'm not getting compressed loads, yet, but I'm definitely beyond the max in any published manual.
I'm using neck sized FC Brass fire formed to my chamber, 155 a-max, xbr and OAL is just shy of AICS un-modified magazine length.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MedicGordo</div><div class="ubbcode-body">Shot it today out of my AI AE 24" worked up to 46gr. Cold bore @ 45gr 2904 #2 2909 45.5gr #1 2937 #2 2940 46gr#1 2975 #2 2978 .155 scenar jammed about .003-.005 46gr had slight primer extrusion to be expected with an AI,bolt lift was perfect.all with br2's.conditions 51degrees 52% r/h 30.30 baro @aprox. 320ft ASL.I shot 46gr of varget the day before with all the same conditions and brass they were running 2780 average.@200 the 46gr load shot 3/8 moa.this is 1 gr. Above max be careful and work your rifle up.JUST SAYING. </div></div>
Have you worked up any loads warmer than 46grains? I worked up to 46 grains today, but was wondering if I could take it much farther. I'm not getting compressed loads, yet, but I'm definitely beyond the max in any published manual.
I'm using neck sized FC Brass fire formed to my chamber, 155 a-max, xbr and OAL is just shy of AICS un-modified magazine length.
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