Barrel Length?

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I found this information and thought I'd share it with you all. The subject is in regards to barrel length and it's effect on velocity. I have often thought of buying a NEF Handi in either .500 S+W or a 30/06 and cutting the barrel down. It would seem that either of those chamberings would be a good choice and lose such a small amount of velocity as to be negligible.
Don

The Remington Catalog 2003 includes a "Centerfire Rifle Velocity Vs. Barrel Length" table that shows the following velocity changes for barrels shorter or longer than the test barrel length:

MV 2000-2500 fps, the approximate change in MV per 1" change in barrel length is 10 fps.
MV 2500-3000 fps, the approximate change in MV per 1" change in barrel length is 20 fps.
MV 3000-3500 fps, the approximate change in MV per 1" change in barrel length is 30 fps.
MV 3500-4000 fps, the approximate change in MV per 1" change in barrel length is 40 fps.

The 45th Edition of the Lyman Reloading Handbook also has a table showing Center Fire Rifle Velocity Vs. Barrel Length. Their figures apply to barrels between 20 and 26 inches in length and agree with the Remington figures. The Lyman table shows the following approximate velocity changes:

For rifles with muzzle velocities in the 1000-2000 fps range, the change in velocity for each 1" change in barrel length is 5 fps.
For rifles with muzzle velocities in the 2001-2500 fps range, the change in velocity for each 1" change in barrel length is 10 fps.
For rifles with muzzle velocities in the 2501-3000 fps range, the change in velocity for each 1" change in barrel length is 20 fps.
For rifles with muzzle velocities in the 3001-3500 fps range, the change in velocity for each 1" change in barrel length is 30 fps.
For rifles with muzzle velocities in the 3501-4000 fps range, the change in velocity for each 1" change in barrel length is 40 fps.

The 43rd edition of the Lyman reloading Handbook gave some concrete examples of velocity loss for specific calibers and loads. The Lyman technicians chronographed some high velocity cartridges in rifles with barrels ranging in length from 26" down to 22" with the following results:

The average loss for the .243 Win./100 grain bullet was 29 fps per inch.
The average loss for the .264 Win. Mag./140 grain bullet was 32 fps per inch.
The average loss for the .300 H&H Mag./220 grain bullet was 25 fps per inch.

For standard high intensity cartridges in the same test, the Lyman technicians chronographed the cartridges in barrel lengths ranging in length from 24" down to 20" with the following results:

The average loss for the .270 Win./130 grain bullet was 37 fps per inch.
The average loss for the .270 Win./150 grain bullet was 32 fps per inch.
The average loss for the .300 Sav./180 grain bullet was 17 fps per inch.
The average loss for the .30-06/180 grain bullet was 15 fps per inch.
The average loss for the .35 Rem./200 grain bullet was 11 fps per inch.

[juliang]

Where did I leave my hacksaw?

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juliang said:

Where did I leave my hacksaw?

LOL-A fine tooth blade makes for a cleaner cut, but if you want to get the job over with nothing beats a nice 18 tooth! ;D
I've been looking at the NEF in 30/06 which has a 22" barrel. Cut down to 18" it would only lose 68FPS total for a 180gr. bullet. Even less with heavier slower bullets. With the short over all length of only 38" with the original 22" barrel, chopping 4" off drops that down to 34" over all. That would be one fast handling brush gun! I wouldn't doubt it might even shoot better with less barrel vibration.
Now the .500 S+W is a different animal altogether, and I do mean animal. Using a 440gr. Cast Performance bullet, the 8" barreled revolver can develop 1650FPS. Now add 10" of barrel length by shooting it from a cut down NEF with an 18" barrel and the velocity moves up maybe 50-75FPS. Another real Handi brush gun.
Don

[GrampaJer]

What causes the loss of FT pounds. If all the powder burns before the projectile leaves the barrel, why a difference. And if all the powder doesn't burn, then why cant a lesser grain charge be used for the same performance... ;D

[juliang]

A lot of people report improvements of accuracy with a shorter barrel, less whip. I am genuinely tempted with the hacksaw. Jer, your question sounds logical, I don't know the answer either.

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tenisiejer said:

What causes the loss of FT pounds.

Jer,
They aren't talking Ft. Lbs., but FPS(Feet Per Second) measuring the velocity.

tenisiejer said:

If all the powder burns before the projectile leaves the barrel, why a difference.;D

When a bullet leaves the barrel, the driving force of the pressure built up behind the bullet in the barrel ceases. Ideally all the powder does burn before the bullet leaves the barrel, the difference between a long barrel and a short barrel is in the pressure created by that burning powder or explained differently, the rapid expansion of the burnt powder behind the bullet. The longer that pressure remains behind the bullet, the more velocity the bullet will achieve. There is however a point of diminishing return when the friction between the barrel and the bullet overcome the driving pressure behind the bullet and it will begin to lose velocity in the barrel. I remember reading many years ago that the barrel length for a 30/06 to reach it's maximum velocity is somewhere in the 30 foot range. Of course once the length of your barrel goes beynd the accepted standard rifle barrel lengths, the gain is too small to be of consequence.
Don

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juliang said:

A lot of people report improvements of accuracy with a shorter barrel, less whip.

That is a fact. The barrels act like a tuning fork and vibrate as the bullet travels down the barrel. The longer and thinner the barrel, the more vibration. That was one reason Browning came up with the BOSS system to tune the barrels harmonics to match the load your using and eliminate the vibrations effect on accuracy. Limbsaver also developed a unique method of dealing with the vibrations. www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=593560&t=11082005

juliang said:

I am genuinely tempted with the hacksaw.

I've done it before! The key is to leave the crown of the muzzle without any burrs. Recrowning can also be a do it yourself project. They sell or even rent recrowning tools for it. I am a bit of a chicken though. I limit myself to cutting down cheaper replaceable barrels like the NEF barrels, just in case I mess it up.
Don

[psycho]

good info guys