Am I thinking about this correctly?

KnotRight

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Last trip to the range I was shooting ammo that I have only shot in an AR platform. When shooting out of a bolt gun with a 18.5" barrel without a flash suppressor I was getting a nice fireball out of the barrel and the gun was a lot louder than shooting it out of the AR-15 platform.

The questions is, should I be using a faster burning powder in the bolt gun? Right now I am shooting a 55 FMJ. Also, I was shooting maybe 3 different powder just to see how the gun shot, H335, Shooter's World Tactical Rifle and maybe Varget.
 
Charlie, Not sure about your reply. Even tho the bolt action is only 2" long than the AR-15, the AR is bleeding off pressure be for the bullet leaves the barrel. A 2" handgun likes faster burning powder than a 6 " barrel.
i would think the same holds true with the rifle.
The fireball is un-bunted powder
 
I do not think that going to a faster powder for which published data are available would make much difference. You have a shorter barrel that does not have a flash suppressor. My first AR is a Colt from a while back that does not have a flash suppressor. It has a much more obvious flash and is louder than the other AR rifles I have that do have flash suppressors. It seems as if the suppressors should not work as well as they do. The loudest AR I have has a muzzle break instead of a flash suppressor. That rifle is obnoxious to shoot.

I have read several places that the powder in a normal pressure load burns before the bullet gets very far down the barrel. You lose velocity with shorter barrels because the pressure has less time to accelerate the bullet and not because the longer barrel allows more of the powder to burn completely. The only large amount of unburned powder I have ever seen is from very low power loads that did not have enough pressure to ignite and burn the chosen powder completely. Light shotgun target loads seem to be the worst for this.

edit: I do not think the amount of pressure bled off to cycle the action has any significant effect on this situation.
 
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