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Barrel lengths vs. Velocity gain/loss

 
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Old 02-24-2011, 01:22 AM
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Barrel lengths vs. Velocity gain/loss

My big question is how much velocity is lost by going with a little shorter barrel. I strongly believe the fact that out of two barrels of the same diameter, but having a two inch difference in length will result in the shorter barrel being more accurate (in theory) because of more barrel stiffness and less vibration.. So if 2" less barrel isn't robbing too much velocity then why not?

I've currently got a rem 700 VLS .22-250 26" barrel. Wanna rebarrel with a 24" kreiger fluted and chambered in .22-250 AI and shoot the new 53gr. VMAX. Obviously the Ackley is faster. I'm looking to make this varminter a bit more handy and lighter in weight.

Lets hear some good input from the guys who know what they are talking about.
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Old 02-24-2011, 03:13 AM
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Re: Barrel lengths vs. Velocity gain/loss

There are WAY too many variables going into this to give a straight yes/no answer.

Plain and Simple, depends on too many things! The old rule of thumb is 30-50 fps per barrel inch. But that is so general, it's kinda useless under today's component list.

Powder burn rate, land/groove diameters, twist rate, bullet weight, primers (hot or cool), on and on and on.......... fast barrel, slow barrel, ect...........tight chamber, loose chamber, long throat, short throat......on and on and on.

FWIW, I've owned and shot a few 22-250's with both 24's and 26's. When you're talking 53 grn bullets, the suitable accuracy powders are burning fast enough that it really doesn't matter (yes, generally speaking the 26's shot a little faster than the 24's), enough to matter to a varmint.......NO.

Now change the subject to 69, 75, 80 grn bullets..........different story, that's really where you need the long barrel and slow burning powders. On the same page, include 22-243's, 22 CHeetahs, 220 Swift Improved, 22-6mm's and the like.........again, this is where we need long barrels and slow powders.
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Last edited by SBruce; 02-24-2011 at 03:23 AM.
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Old 02-24-2011, 03:30 AM
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Re: Barrel lengths vs. Velocity gain/loss

My buddy has done a great deal of experimenting with this. He would chamber a new barrel and crown it off. Work up the best load he could find them chronograph it. He would then put it back in the lathe part off an inch and recrown and work up a load and chronograph. I do not know how much value his results have on larger cases, but his results showed an average of 17fps per inch in 6PPC for five inches of barrel removed.
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Old 02-24-2011, 06:26 AM
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Re: Barrel lengths vs. Velocity gain/loss

Quote:
Originally Posted by eddybo View Post
My buddy has done a great deal of experimenting with this. He would chamber a new barrel and crown it off. Work up the best load he could find them chronograph it. He would then put it back in the lathe part off an inch and recrown and work up a load and chronograph. I do not know how much value his results have on larger cases, but his results showed an average of 17fps per inch in 6PPC for five inches of barrel removed.
Some time ago I saw an experiment where a smith did this, removed one inch of barrel at a time, and reported an average loss of 25 fps per inch. There are variables.

I like short 20" barrels , for BR rifles out to 300 yds., because, generally - they balance better and the vibration nodes are shorter. Beyond that distance, I feel the added velocity is an advantage, and prefer 26" barrels.
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Old 02-24-2011, 08:06 AM
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Re: Barrel lengths vs. Velocity gain/loss

My opinion is the same as stated before, more of a matter of drag, amount and size of lands and grooves, bullet weight, seating depth, powder burn rate, etc. Every caliber is different. Honestly going to the AI version is ******* in the wind, nothing you shoot with that particular bullet from either version will ever know the difference!
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Old 02-24-2011, 08:14 AM
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Re: Barrel lengths vs. Velocity gain/loss

Mr. Lilja of Lilja barrels performed that very same experiment and documented his results here:

Lilja Precision Rifle Barrels - Articles: Barrel Lenghts and Velocities in the 338/378 Weatherby Magnum

interesting. The results are, in part, based in part on the powder burned, case capacity, and bullet weight.

Jeffvn
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Old 02-24-2011, 01:03 PM
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Re: Barrel lengths vs. Velocity gain/loss

Quote:
Originally Posted by jhibbard24 View Post
My big question is how much velocity is lost by going with a little shorter barrel. I strongly believe the fact that out of two barrels of the same diameter, but having a two inch difference in length will result in the shorter barrel being more accurate (in theory) because of more barrel stiffness and less vibration.. So if 2" less barrel isn't robbing too much velocity then why not?

I've currently got a rem 700 VLS .22-250 26" barrel. Wanna rebarrel with a 24" kreiger fluted and chambered in .22-250 AI and shoot the new 53gr. VMAX. Obviously the Ackley is faster. I'm looking to make this varminter a bit more handy and lighter in weight.

Lets hear some good input from the guys who know what they are talking about.
quite honestly a 26" barrel in a 22-250 is nothing more than a barrel harmonics disaster looking for a place to happen. The .250 savage case is not exactly a big case, and is known to work quite well with a 22" barrel, so a 24" barrel should be plenty of barrel even with the Ackley case.

A given barrel profile will be stiffer the shorter it is verses the the same contour but longer. A typical #7 contour 21" long is 2.75 times stiffer than the samething 26" long (275%). A 24" barrel will probably be 33% stiffer, making everything group a little better. The stiffer the barrel, the more controll it has over harmonics.
When you goto the shorter and stiffer profile, you simply adjust the powder burning range you work out of. With today's huge array of powders, this shouldn't be much of a problem with the .250 case. It might with a .300 mag case.

I shortened a .223 barrel six inches, and lost a huge 75 fps! (not close to a max load by the way). Still use the same three or four basic powders I was using before, and everything's better with it. Plus the balance is so good that I can shoot a heavy barrel offhand without any trouble what so ever.
gary
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