Barrel Length vs Muzzle Velocity

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lackeyse

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Since I don't have a chrony and I am naturally curious as to what kind of velocities that my rifle/ammo combination produce I did a little online research for any info.

According to one of the sites that I visited, barrel length vs muzzle velocity is a complex relationship but overall the variance in barrel lengths do not have an ENORMOUS impact on muzzle velocity but does make a difference.

I have heard varying opinions regarding this subject with some people claiming as much as 100fps or more in velocity change with only a 1" difference in barrel length.

Any thoughts on this topic?

Here is what I read:

http://www.loadammo.com/Topics/October05.htm

Sorry if this topic has been beaten to death:runaway:
 
30-30 Winchester, Handgun
H4895, 30.5 grains, 170 grain bullet. 1896FPS


30-30 Winchester, Rifle
H4895 30.5 grains, 170 grain bullet 2138 fps.

Sadly, I don't see the respective barrel lengths listed on Hogdons site, the source of this data.

I think, in the manual, the handgun was a 14" barreled TC Contender, and the Rifle, a 20" Marlin Carbine.

The cartridge powder capacity, the bore size, the bullet weight, the bore condition, and probably a thousand other things will effect this.
 
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I have two 308 M70's one with a 20" the other with a 26" barrel they shoot the same 165 grain load at 2628fps and 2694fps respectively. A difference of 11 fps per inch.
 
The change in velocity depends on the barrel make, twist rate, caliber and how the chamber is cut. Length isn't everything... One barrel may only see 10fps/inch difference while the other sees 50fps/inch difference. One manufacturer's 20" barrel may shoot faster than another's 26" barrel for the same caliber, same load, same twist rate.
 
Barrel length has much more effect on velocity and accuracy when using the slower burning powders for a load.

If the peak pressure is still on when the bullet exits the barrel, 4 inches can make a big difference.

A fast burning powder would work better in a short barrel.

I notice that when I load more powder - even a fairly fast burning powder, the peak pressure is later in the barrel - causing more flash and boom. Getting a further increase in velocity may require a little faster burning powder - which will start a whole new pressure curve.

Load up a few and make friends with a guy with a chrony.
 
One of my manuals gives a ballpark based on initial mv - the higher the velocity, the more that is lost per inch shortened. One the other hand, I have a short 6.5x55 that loses even more than the book suggested - 180 fps for the loss of 4" of bbl which this particular table suggests ought to be more like 80.
 
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