Effect of Barrel Length

[Creedmoor]

Gentlemen / Ladies,

I am looking to get a couple of new rifles and was wondering about the effect of barrel length on velocity.  I have heard that conventional wisdom says you give up about 25 fps for each 1 inch reduction in barrel length.  But I have also heard that beyond a certain length you don?t gain any velocity and may lose some.  I?m assuming either or both of these truisms may not hold for all calibers.  Hence my questions:  For 30-06, if I go with an 18 inch barrel vs. the standard 22 inch barrel what would I lose?  For 22 Hornet, what is the trade-off between a 20 inch barrel and a 24 inch barrel?

Any advice is much appreciated.  Thanks

[Iowegan]

Many tests have been conducted on this very topic.  I've seen mixed data because a XX inch barrel was compared to a XX inch barrel in a totally different gun. The only real good test I've seen was when a 24 inch 30-'06 was chronographed, tested for group size, then cut off. Each half inch barrel cut was chronographed and grouped with a variety of different weight bullets and documented. The cuts continued to 16" (minimum legal length). Velocity decreased with each cut, but not a fixed amount.

Lighter weight bullets suffered the most loss in velocity. This is because they have more powder to burn and they are higher velocity to start with. Bottom line, you won't loose enough velocity in a hunting gun to worry about. Accuracy was not affected much, in fact it improved at some barrel lengths. For long range and tactical shooters, they want all the length they can get.

I have also read that a 30-'06 would continue to gain velocity up to a 36" barrel. Now that would be a bugger to tote around!

[lilabner]

The 25 fps rule of thumb is for cartridges in the 30-06 class. Magnums suffer a greater loss with short barrels and that is why they are normally offered with 24 or 26 inch barrels. There is more powder to be burned in magnums and that requires a longer barrel. The .22 rimfire achieves its highest velocity at about 16-18 inches. At that point the powder has burned and drag starts slowing the bullet down. Just a guess but I suspect the Hornet would not lose as much velocity as a 30-06.

[Duffy]

With my 15" 22K Hornet bbl I am able to pretty much obtain what the longer bbl's can. Barrel finish and size has quite a bit to do with it also. Fred at bullberry has done a test with the 204 ruger on bbl length and it does not seem to tolerate short bbls as well as others. I do know that my bil's 270 with a 24" bbl is about 150+ fps faster than my 22" with the same load.

[Jack Crevalle]

If you look at the two powders I most often see recommended for the .22 Hornet, 296 and Lil'Gun, one is a pistol powder and the other is (or was developed originally as,) a shotgun powder. Since these are both I would assume, fast burning powders I would think that barrel length would have little effect on velocity with them.

[george]

I have also read that a 30-'06 would continue to gain velocity up to a 36" barrel. Now that would be a bugger to tote around!

Hard to carry, but once setup on the sandbags that would be mmmm...sweeeeet off the bench! :grin:

[Lone Star]

If you look at the two powders I most often see recommended for the .22 Hornet, 296 and Lil'Gun...these are both I would assume, fast burning powders I would think that barrel length would have little effect on velocity with them.

The two powders are "fast burning" if you compare them with magnum rifle powders, but they are considered slow burning in the .22 Hornet.  

All appropriate powders are effected by barrel length, but the rate of loss depends on the original length.  Accurate Arms data for their 1680 powder (close to Lil' Gun in burning rate) shows a 388 fps loss going from a 24" barrel to a 10" barrel; that's 28 fps/inch.  The rate of difference going from 24" to 20" would be less.