Twist Rate Newbie

[modraker]

Alright, I've been shooting for years but only lately paid attention to the finer points of accuracy. I gather from forum posts that S&W has recently changed their barrel twist rate for the 9mm from 1 in 18.75" to 1 in 10". If I shoot primarily 124 gr FMJ, which barrel am I better off using?

 

[OKFC05]

Does not make the slightest bit of difference at usual pistol speeds and distances using your 124gr jacketed bullets.

With plain lead the slower twist is slightly better in theory, since there is less tendency to "strip" the bullet and lead the barrel.

If you shoot the longer 147gr at slower speed to barely make minor power in an action pistol game, the faster twist has the advantage, giving the long, slow bullet more stability. This is what really motivated the change in the M&P.

People who shoot 115gr and 124gr 9mm bullets at normal speeds will never know the difference between the 2 twist M&P barrels.

Those of us who have shot target blackpowder guns have had to learn twist rates to match our choice in bullets and loads to our barrels to reliably hit anything at long range. You don't think we shoot those large charges behind heavy bullets just for "kicks", do you?

 

[Denversteve]

Does not make the slightest bit of difference at usual pistol speeds and distances ...

True. Focus on perfect technique to hone your accuracy skills.

 

[noammo]

In a nutshell, if the bullet spins too slowly, it becomes unstable. If the bullet spins too fast the nose of the bullet will not follow the arc of trajectory. It will fall sideways, so to speak.

 

[mx5rcr]

I don't think that S&W would have gone through the trouble of changing barrel twist if it didn't matter. Tpically I have found that service pistols are designed for use with service spec ammo. I think that is usually going to be 124gr and maybe +P since that is what their main clients will be using. I don't think there are too many LE or .mil types using Winchester White box 115 grain range ammo on duty.

 

[MichiganScott]

Seems to me that 1 in 18.75 has been standard in .38 Special/.357 Magnum since forever. Bullets for the Special/Magnum have ranged from 95gr to 200gr. Nobody seems to complain too much.

 

[DocSunShine]

Seems to me that 1 in 18.75 has been standard in .38 Special/.357 Magnum since forever. Bullets for the Special/Magnum have ranged from 95gr to 200gr. Nobody seems to complain too much.

Too many accounts of the 1/18.75 twist causing problems in 9mm M&Ps, I'm very impressed Smith has listened to the consumer not only fixing this issue, dramatically improving the trigger as well. I don't even feel the need to put anything apex on a current production stock trigger, that's saying a lot. Now if only they get the magazine situation squared away (and according to S&W reps today when I bought my CORE, mags are on their way)...