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Old September 9, 2012, 05:40 PM   #27
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Join Date: July 20, 2005
Location: Indiana
Posts: 10,170
Originally posted by Blue Train
To WebleyMkV, while what you say is correct in that a faster burning powder is more efficient in a shorter barrel, because it's more likely to all be burned within the barrel, I don't think that's necessarily the way to measure efficiency. It may or may not be true that the faster burning powder will produce a higher velocity, though it will probably produce less muzzle flash or blast. I would be more likely to believe that a heavier charge of slower burning powder may in fact produce a higher velocity even at the cost of less efficiency as far as burning powder is concerned. Even so, there's more to it than that.
The key to getting the highest possible velocity is maintaining peak pressure for as long as possible. Whether a fast burning powder or slow burning powder is best for the task depends on both bullet weight and barrel length. Generally, for light bullets and/or short barrels, faster burning powder is preferable. This is because pressure is at or peak when the bullet leaves the case and the powder is mostly, if not completely, burned by the time the bullet leaves the barrel. Slower burning powders are not preferable for short barrels or light bullets because the bullet will likely be well down if not out of the barrel and a good percentage of the powder will burn after the bullet has already left the barrel.

Conversely, slower powders are better for longer barrels and/or heavier bullets. This is because a larger percentage of the powder will burn before the bullet exits the case, thus ensuring that peak pressure is not reached too soon, and because the powder will continue to burn until the bullet is out, or almost out, of the barrel. Slower burning powders are less preferable for light bullets and short barrels because peak pressure is likely to be reached well before the bullet leaves the case, thus reducing the length of time it can be maintained while the bullet travels down the barrel, and because the powder will likely we burnt up well before the bullet exits the barrel thus reducing pressure quickly and allowing the friction of the barrel to slow the bullet's velocity.

If you have a variety of handguns, particularly of the same caliber, you may not want to customize the loads that much. In other words, there's no point in having the same caliber if you use different loads in different guns, though I still understand the object. One might want to use different loads even though you only had one gun. In addition to having a load suitable for shooting 1957 Chevrolets, which would be detestible, you might still have use for wadcutters in your pet .357 revolver.
Sticking to one loading for a given caliber is understandable enough as I do it myself. Both my 2 1/2" S&W M66 and my 4" M28 are loaded with Remington 158gr SJHP. This loading is among the most efficient in my snub and I do not feel that it is markedly inferior to lighter, faster .357 Magnum loadings even from a longer barrel. Of course, I've long thought that 158gr bullets were the best "all purpose" weight for a .357 Magnum.

Ultimately, you can only measure the efficiency of the load by measuring the velocity of the load--in your own gun. That's true for factory ammo, too, about which you may not know anything about the powder. Of course, muzzle flash and blast can still be a concern that you will still want to take into account no matter what the velocity comes out to be.
Yet another reason that I prefer the heavier 140-158gr bullets in a .357 Magnum is that, with full power loadings, the blast and flash does not seem nearly as pronounced though they're still not what I'd describe as "kind and gentle".
Smith, and Wesson, and Me. -H. Callahan
Well waddaya know, one buwwet weft! -E. Fudd
All bad precedents begin as justifiable measures. -J. Caesar

Last edited by Webleymkv; September 10, 2012 at 07:39 AM. Reason: typo
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