Curry Mosher
32 Cal.
- Joined
- Oct 4, 2003
- Messages
- 27
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The following is from the "Rifle your barrel at home" article by Fred Stutzenberger and Robert Mims in the January 2001 issue of "Muzzle Blasts"--
Begin Quote--The rifling pitch (rate of twist) in rifle barrels ranges nominally from one revolution in 42 inches up to one in 72 inches for the patched round ball, and from one in 18 inches to one in 36 inches for elongated bullets. For pistol barrels, where the powder charge might be one-half that of a comparable rifle, the rate of twist might be one in 16 to one in 30 inches. Sir Alfred George Greenhill (1847-1927) proposed a formula in 1879 for the calculation of optimal rifling twist using either round or elongated bullets of pure lead with a specific gravity of 11.35:Optimal twist (inches/rev) = 150 x caliber x (D/L) where D and L are bullet diameter and bullet length, respectively. Of course, for a round ball, diameter equals length and the equation reduces to 150 x caliber. So, for a fifty-caliber rifle using a .490 ball, the optimal twist would be about one revolution in 73 inches. End Quote.
I read a post the other day that talked about the formula for twist, so when I was looking through an old "Muzzle Blasts" and ran across this, I just had to post it.
Begin Quote--The rifling pitch (rate of twist) in rifle barrels ranges nominally from one revolution in 42 inches up to one in 72 inches for the patched round ball, and from one in 18 inches to one in 36 inches for elongated bullets. For pistol barrels, where the powder charge might be one-half that of a comparable rifle, the rate of twist might be one in 16 to one in 30 inches. Sir Alfred George Greenhill (1847-1927) proposed a formula in 1879 for the calculation of optimal rifling twist using either round or elongated bullets of pure lead with a specific gravity of 11.35:Optimal twist (inches/rev) = 150 x caliber x (D/L) where D and L are bullet diameter and bullet length, respectively. Of course, for a round ball, diameter equals length and the equation reduces to 150 x caliber. So, for a fifty-caliber rifle using a .490 ball, the optimal twist would be about one revolution in 73 inches. End Quote.
I read a post the other day that talked about the formula for twist, so when I was looking through an old "Muzzle Blasts" and ran across this, I just had to post it.
