[bg226]

In 9mm.

Given the same load and rifling, would barrel length make a significant difference in velocity?

Anyone have some numbers for 3.5", 4.0" and 4.5" barrels?

Thanks :)

[Mad Magyar]

"make a significant difference in velocity?"

No, the same with accuracy....The key word is "significant"...

[1911Tuner]

For autopistols...given the relatively quick powders typically used...figure on about 25 fps per inch, all else being equal..which it usually isn't. For the magnum revolver calibers...figure on about 35-40 fps per inch. The slower the powder burn rate, the more difference that added barrel length increases velocity. F'rinstance...a 160-grain .357 caliber bullet pushed by a max pressure charge of Bullseye will gain less velocity per inch between a 3 inch and a 6-inch barrel than it will with a max pressure charge of 2400. The slower powder holds its peak pressure longer, with more area under the curve, while the faster powder peaks quickly and drops quickly. The faster powder will beat the slower one out of the hole, but the slower powder passes it on the top-end, after the peak. Or...another way...A .357 magnum
will gain about 75 or 80 fps between 3 and 6 inches with Bullseye, and
about 100 fps if loaded with 2400, assuming identical bullets.

For rifles in the .308/.30-06 class...figure on about 20-25 fps per inch. Magnum-class rifles like .300 Win Mag or 7mm Remington, go a little higher.

Other factors come into play as well. No two guns are alike, and it's entirely possible to get equal or higher velocities from a 4-inch revolver than with a 6-inch. Or...you might get higher exit speeds with a heavy bullet in the longer barrel, and have it reversed with a light bullet.

Ain't ballistics interestin'?:cool:

[JohnKSa]

Also keep in mind that the rifling type can have an effect on velocity--one maker of compact 9mm pistols (Kahr) uses polygonal rifling and claims that it largely compensates for the velocity loss from the shortened barrels.