9mm pistol barrel twist?

[MH64]

So what do most pistol manufacturers use as the twist rate in 9mm handguns?

[skyugo]

glock and HK use about 1 in 10.

[LightningFast]

glock and HK use about 1 in 10.

Yep. CZ 75 and the like use it as well.

S&W M&P uses something like 1 in 18.5, IIRC.

[skyugo]

Yep. CZ 75 and the like use it as well.

S&W M&P uses something like 1 in 18.5, IIRC.

hmm that's quite a bit slower. interesting

[TiroFijo]

From a gyroscopic stability standpoint, 1-18.5" is plenty. S&W uses 1-18.75" for 38 spl and 357 mag, which use longer, heavier bullets across an extremely wide velocity range with excellent resutls. There are custom barrels that use even slower twists, looking for best accuracy. The 9 mm bullets are relatively short and very easy to stabilize, and the reason 1-10" is the standard is simply tradition, NOT reasoning.

If the S&W MP 9 mm pistols have some accuracy problems, it is likely due to other reasons, not twist. The vertical spread that some report is an indication of early unlocking.

[LightningFast]

From a gyroscopic stability standpoint, 1-18.5" is plenty. S&W uses 1-18.75" for 38 spl and 357 mag, which use longer, heavier bullets across an extremely wide velocity range with excellent resutls. There are custom barrels that use even slower twists, looking for best accuracy. The 9 mm bullets are relatively short and very easy to stabilize, and the reason 1-10" is the standard is simply tradition, NOT reasoning.

If the S&W MP 9 mm pistols have some accuracy problems, it is likely due to other reasons, not twist. The vertical spread that some report is an indication of early unlocking.

From what I've researched and gathered, the contrary proves true. High speed video testing showed inconsistent unlocking, not consistently early.
Also, if stabilization is not the issue... why do almost all M&Ps shoot well with heavier grain bullets (147), but it is a crap-shoot with 115s?

[skyugo]

From a gyroscopic stability standpoint, 1-18.5" is plenty. S&W uses 1-18.75" for 38 spl and 357 mag, which use longer, heavier bullets across an extremely wide velocity range with excellent resutls. There are custom barrels that use even slower twists, looking for best accuracy. The 9 mm bullets are relatively short and very easy to stabilize, and the reason 1-10" is the standard is simply tradition, NOT reasoning.

If the S&W MP 9 mm pistols have some accuracy problems, it is likely due to other reasons, not twist. The vertical spread that some report is an indication of early unlocking.

I kind of doubt that twist rate would have a lot of effect one way or the other at pistol velocities and ranges...

agreed, the m&ps with issues probably have something weird going on at lockup/unlock. Honestly every M&P 9 i've shot (3-4 of em) have been tack drivers though. I always go through a brief period of wanting to ditch my g19 and go full M&P after shooting one.

[saddlerocker]

From what I've researched and gathered, the contrary proves true. High speed video testing showed inconsistent unlocking, not consistently early.
Also, if stabilization is not the issue... why do almost all M&Ps shoot well with heavier grain bullets (147), but it is a crap-shoot with 115s?

If a slow twist rate was an issue the opposite would be true.
115gr would be better than 147gr

[TiroFijo]

From what I've researched and gathered, the contrary proves true. High speed video testing showed inconsistent unlocking, not consistently early.
Also, if stabilization is not the issue... why do almost all M&Ps shoot well with heavier grain bullets (147), but it is a crap-shoot with 115s?

when I read things like "almost all M&Ps" I wonder what is really the statistical certainty of this claim...

I haven't seen any high speed videos of these pistols, do you have a source or a link? I wonder how "inconsistent unlocking" would happen without the "early" part. I don't see it possible, the unlocking timing is basically fixed based on the momentum equilibrium of the accelerating bullet and powder mass and the mass of the slide+barrel, and the geometry of the unlocking mechanism.

[spr1]

When questions of the M&P's 9mm twist rate come up, I always think that if S&W wanted to ensure that the twist rate was not a problem, that instead of doing any calculations and testing, that they should just copy HK and then spend their time worrying about things like unlocking.......