A little history before the question. Someone I know is at A sniper school right now. He is shooting A Rem. 700 PSS in .308 Factory Federal Match Ammo. One of his instructors told him if he had 5 inches of his rifle barrel cut off that his gun would shoot more accuratly and the bullets would go faster. Now I'm hearing this second hand so the person telling me or the shooter at school might not have heard right but, is there anyway that this is possible.
The gun shoots good right now but cutting the barrel off could make it shoot better or not. But I can't see how the bullets would travel faster with that short of a barrel, but you would gain a lot of muzzle blast. What do you think about this.

quote:

Originally posted by 257 Rock:
A little history before the question. Someone I know is at A sniper school right now. He is shooting A Rem. 700 PSS in .308 Factory Federal Match Ammo. One of his instructors told him if he had 5 inches of his rifle barrel cut off that his gun would shoot more accuratly and the bullets would go faster. Now I'm hearing this second hand so the person telling me or the shooter at school might not have heard right but, is there anyway that this is possible.
The gun shoots good right now but cutting the barrel off could make it shoot better or not. But I can't see how the bullets would travel faster with that short of a barrel, but you would gain a lot of muzzle blast. What do you think about this.

Someone must have misunderstood!

Sure, if he starts with a 40" barrel.

Here's the chart showing the relationship of velocity versus barrel length for the 223. You can see that it maxes out velocity at about 38" and then starts slowing down. I'm sure someone can find one for the the 308 military load.

quote:

One of his instructors told him if he had 5 inches of his rifle barrel cut off that his gun would shoot more accuratly

It is highly possible that it could shoot more accurately. Shorter barrel less swing from vibration. Most BR barrels are short compared to hunting rifles. There is a magic number that BRs swear by but the exact number excapes me at the moment. Higher speed I can't see how.

Sounds like "instructor bullshit" to me.

They are not all experts at everything. And NO there is NO way the bullet is going to go faster.

His instructor posts here as rem721

quote:

Originally posted by duikerman:
His instructor posts here as rem721

I doubt either would happen. Cutting off a slim, whippy barrel to make it stiffer will often increase accuracy, but it may not do so with a heavy, target-weight tube. In addition, for a round like the .308 Win., we say a rule of thumb is that velocity is gained by the ADDITION of more barrel length, at the rate of about 25 feet per second per inch, and is lost at about the same amount for each inch REMOVED from a barrel.

Like all rules of thumb, however, sometimes it just doesn't happen this way, and it is POSSIBLE to gain some velocity, or perhaps not lose any, by cutting a barrel.

A lot depends on the case capacity and caliber of the round in question, and the amount and type of propellant. For example, a HV .22 long rifle round produces its' maximum velocity in an 18" barrel, and a longer barrel actually SLOWS the bullet down by friction before it exits the muzzle. The greater the length by which the barrel here exceeds 18", the slower the bullet at the muzzle. Same situation as the .223 cal. chart shown above by Fjold, different barrel lengths.