At what point does barrel length become a moot point?

T

tpcollins

New member
When I look at reloading balistics, there's usually some reference of a 26" barrel used in testing, but I'm not sure that's the golden rule. When I shot some Hornady .204 V-Max with my Tikka 22 1/4" barrel, my velocity was about 400 fps slower, as expected, from the factory advertised 4225 fps.

But is there sort of a diminishing return that after a certain length, more barrel length does not generate a significant amount of increased velocity? Any insight would be appreciated, thanks.
 
Usually for ballistics the ratio of barrel length/caliber is the important number. For a tiny round like the .204 your 22.5" barrel is 100+ caliber length, plenty into the diminishing return area. While a .458 with a 26" barrel only gets up to a 55 ratio, and will probably see improvements way out to impractical 32"+ barrels.
 
Usually for ballistics the ratio of barrel length/caliber is the important number
Click to expand...
What is most important is the amount of powder in relation to the volume of the bore. If you still have expanding powder pushing the bullet, it will keep gaining velocity. If you don't, it won't. There is a big difference in the amount of powder behind a 45 acp and a 460 Weatherby or a 50 AE and a 50 BMG.

Most rifle rounds will continue to gain velocity until the barrel length is much longer than what is practical. Imo, when it becomes a moot point depends on how you intend to use the rifle.
 
Until maybe the 1970s, cartridge velocities for rifles were published with a 26" barrel as the standard. I know Remington and Winchester used to provide gunshops with foam-backed plastic mats which had their cartridges' muzzle velocities and energies printed on them.

With the growth of independent powder companies besides DuPont and Hercules, and then the independent cartridge manufacturers, testing for muzzle velocities in the reloading manuals began showing lesser-length barrels.

Nowadays, I guess you could say that there's no such thing as "the" standard length barrel.
 
The upper limit would of velocity would be however fast the gas is expanding. I don't have the numbers in front of me but nitrocellulose gas expands at a known velocity (probably close to around 5000-5500 fps). The bullet can't go faster than this. The force of the expanding gas is opposed by the inertia of the bullet and friction. Every caliber could then have a velocity vs barrel length curve. Certainly not a linear function.

But is there sort of a diminishing return that after a certain length, more barrel length does not generate a significant amount of increased velocity
Click to expand...

Yea there sure is. Probably much longer than what you would ever want to tote around. Once you get above 30" of barrel any increase in velocity is not worth it.
 
I enjoyed the above article about rifle barrels. I have also studied "Ballistics by the inch" and although that is concerning pistol callibers there are some things to be learned from it that can be applied to any firearm.

One thing that hasn't been mentioned yet is the amount of time the bullet is in a section of barrel. Increasing velocity is by transferring energy from the powder charge to the bullet and this takes time. The bullet is not in any section of barrel for very long after it has traveled just a few inches and this time decreases for the next section for every gain in velocity from the preceeding section. Hope this makes sense.

Interesting subject.
James
 
FWIW, I read 'somewhere' that someone had done a "ballistics by the inch" type test with .22lr rifles, using a chronograph, and found that the optimum barrel length was around 16-18". Longer than that and velocities fell off. Just one example.
 
Dave, actually we (BBTI) just did .22s. 10 different ammos, 20 different "real world" guns as well as our 'chop test'. Did it this last weekend.

The data needs to be crunched, and it'll be a few weeks before we get it uploaded to the website. But I can say that the preliminary look at the data sheets indicates that the profile for the .22 is very similar to the profile for the .45 ACP, in terms of the gain of velocity quickly and then a relatively flat plateau. There is a gain all the way past 18", but it is pretty slight.

And other than the Aguila SSS (which is designed to be a subsonic load), none of the ammunition types tested lived up to manufacturer's claims that we could tell.

I will post something when we have the actual data sets ready.
 
You must log in or register to reply here.
Back
Top