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leper
March 05, 2017, 11:46
1;16 twist. spinta is making them now, why the slow twist?
jl

kev
March 06, 2017, 10:09
Pistol caliber. A better question would be 'why a 10" twist in a 9mm?' which is more common, but unnecessarily fast. There never was a good reason for that twist, other than it was 'foreign' and that's what it's always been.

If you look at every other pistol caliber you'll find that they're all 1:16, 1:18, 1:20,......the 9mm is the oddball. No reason it won't work perfectly fine with the slower twist. In fact, that 1:10 twist is the reason that the 9mm has a reputation for not handling cast bullets well.

One other oddball is the .44 Mag, at least in the Ruger Carbines. Those barrels have an unnecessarily slow twist, carried over from the old blackpowder, lead bullet .44-40. Instead of the standard 1:20 they use a slow 1:38 and don't shoot particular well with anything other than max power jacketed loads and won't shoot overweight slugs at all. Why would Ruger do this, especially when they used the correct twist in all their .44 Mag revolvers? Because designers don't pay much attention to what they're doing and generally fall back on what was done before without really understanding the reasons for it.

1:16 will be fine in any 9mm barrel unless you want to load 250gr slugs.

jhend170
March 06, 2017, 11:02
Twist rates are all about projo length. The shorter the projo, the less twist necessary to stabilize. Pistol calibers all have short projectiles so fast rates aren't necessary. People often mistake weight with length. Well, when you're limited by the diameter of something the only way to make a heavier version is by making it longer. This is why you see heavier bullet weights needing faster twists, because they are longer, not because they are heavier. Extend this a bit further and non-lead projos can also do better in faster twists than their lead weight twin, because they have to be longer to get to a particular weight, when compared to lead.

leper
March 06, 2017, 22:10
Thanks, i had thought perhaps there was some load that worked best in the slower twist and 9mm shooters were clamoring for it.
Anyways, it looks like a good deal, so may spring for one.
Jl