Ballisticians expertice needed.

What would be the optimum barrel length for a 20cal cartridge on the 221 Fireball case.

I have a 20 VarTarg with a 25 1/4 in barrel and burn 19.2gn 4198 behind a 35gn Berger for 3730fps.
This rifle was built on a XR100 Rem 204 that we shortened the 26in barrel of to rechamber to 20 VarTarg. Get exceptional performance but here in New Zealand we are freely able to have a supressor fitted and which I would like to do but the over all length would be onerous with a barrel left this length. I would like to have it shortened and would apreciate advise as to what length would best give complete powder burn without compromising performance.

Von Gruff.

All of the powder "burns" within the first few inches of bullet travel. The function of the rest of the barrel is to contain the expanding gases so that they can act longer on accelerating the bullet.

Generally, the smaller the bore relative to the amount of powder, the more benefit barrel length gives you, i.e., a 243 Winchester needs a longer barrel to reach optimum velocity than a .358 Winchester made on the identical case.

That said, cutting the barrel of a .20/221 back to 18 or 20 inches in order to accomodate a suppressor won't cost you all that much velocity. The more appropriate overall length of the gun will more than make up for the relatively few fps lost to the shorter barrel.

I would cut it off a little at a time, maybe 1" increments and chronograph it until you get to a point that you don't want to lose any more velocity. Any other method would be based on a wild ass guess and might ruin your rifle for your intended uses.

There are alot of 22" barreled 204's around that loose little to nothing over a 26" barrel, and a 204 has alot more powder than a Vartag. If I was a betting man, I would wager you would not loose 50fps with a 20" barrel opver a 24" barrel with a 20 Vartag.

Thanks for thoughts. I have posted this question on a couple of forums I visit and the consensus is that 21in should be about right. The surpressor will be 4in forward of barrel with 8in over barrel so oal will be about the same.

Von Gruff.

Fred Smith at www.bullberry.com did a test on the barrel length/velocity on a 204 Ruger and shows the velocity with incriments shortening 1" at a time on the website. I don't know the difference in the 20-221 and the 204 but thought this might help.

God Bless, Louis