Originally Posted By rjrivero:
Here is a twist rate calculator.
The 147gr bullets I have on hand are 0.662 inches in length. The diameter is .355. The last time I chrono'd these bullets, they went 1050 FPS. (A bit Hot, I know, but that's what my Glock likes, and they're still sub-sonic for suppressor use.
When I plug this into the equation, then the calculator spits out 16.9"
I don't know if this is scientific enough or not, but it makes me wonder why we put the 1:10 twist rate in the rest of the 9mm barrels. I don't know the answer for that......
Not to hijack the thread, but can you help me understand that calculator? For s&g's, I put in a typical 9mm pistol projectile but gave it a muzzle velocity of 3000fps, and the calculator gave me a twist output number of 40. Would that indicate a 1 in 40 twist rate?