Ballistics for 21" carbine?

[sman]

Are the ballistics effected very much in a 21inch barrel compared to a longer barrel?

[simonkenton]

Dixie Gun Works did a study on this some years ago.
Got a 30 inch barreled rifle, fired a few shots, then sawed an inch off, fired a few more shots, etc.
They got down to a 16 inch barrel, they were using a chronograph.

Without trying to dig up that study, which may be printed in the Catalog, I recall that the loss from 28 inch barrel to 21 inch barrel is not that bad.
Off the top of my head, I will say you would get a 10 percent velocity loss, might have been more like 8 percent.

So it is reasonable to shoot, and hunt with a 21 inch barrel muzzleloader.

As I also recall, the amount of power gained by going from a 28 inch barrel, to a 42 inch barrel, was negligible.

[necchi]

Off the top of my head, I will say you would get a 10 percent velocity loss, might have been more like 8 percent.

As I also recall, the amount of power gained by going from a 28 inch barrel, to a 42 inch barrel, was negligible.

 I didn't think it was even that much, I kinda remember about 65fps per inch velocity lost from whatever test barrel they used too whatever you have.
 But ya have to consider the entire ballistic thing going on with barrel length, twist rate and velocity combined. Velocity is just one factor. The next issue with PRB is the projectiles ability to grip the rifleing and spin while it's in the barrel. It does little good to increase velocity,aka: heavier charge, if the prb (or what ever) skips,,
 Sufice too common knowledge, carbines are short range "Accurate" guns, they where and are made for close in work. I'm gonna stick my neck out and say 50yrd accurate,,much beyond that and your group will open significantly.

[deadrabbit]

I always thought you needed the barrel length to burn up all the powder?  A 21" barrel does sound nice though.

[simonkenton]

You might be right, necchi, it might have been just 65 fps lost from the 28 inch barrel to the 21.
It wasn't much, it surprised me.
You did begin to get significant loss of velocity going from 21 inch barrel to 16 inch.

[coyotejoe]

The shortest barrel listed in the "Lyman Blackpowder Handbook" is 22" and since it is a fast twist barrel they tested it only with conical and sabot bullets. With a 350 grain conical and 100 grains of Goex 2f it gets 1440 fps and 1612 ft.lb. of energy. The same load from a 28" barrel goes 1503 fps for 1756 ft.lb. of energy. That's not enough difference to be troubling but I'd hate to guess what the recoil would be from a light carbine.

[Walks with Fire]

Green Mountain did a test on barrels shortened in 2" increments down to 20" length; these were the LRH 1/28 twist .50 caliber barrels; percussion/80 grains pryro. The barrels retained accuracy just fine but the velocity loss was a consistant 13.5 fps. per inch. So a 20" barrel would lose 108 fps to the 28" barrel. You might still be able to find the article online. It was titled "It's all in the barrel". I will look for it when I get done looking around on the forum. I am pretty sure I saved it as I have a couple of their barrels; one is 24" and the other is 28". Fifty feet per second doesn't mean much to a roundball but it does to me in a saboted load. You just can't burn enough powder to get any gains in the shorter barrels but they are a bunch nicer to hunt with. I dumped a doe with the 24" barrel with 80 grains of Goex 3f under a 200 grain xtp and it did not go anywhere but down.

http://www.blackpowderjournal.com/archives/vol2no4/articles/BPJ24-5.htm.  Link is broken so click on View cached copy when it comes up.