20 cal twist rate/bullet?

[MrMajestic]

As was stated previously, RPM's will produce spectacular terminal ballistics. When my 8 1/2tw was new I pushed the 39 grain BlitzKings at 4123 fps and they would completely remove a chucks head when hit! When I got some mileage on it they stopped making it to the target.

 

[Tommie]

Ive decided to build a 20 cal AR upper...

Not many choices, 20 practical or 20 tactical... i doubt a vartarg would run through an AR magazine Ha! So it will probably be a 20 tactical.

What twist rate? 12?

I want small and fast! 32 gr vmax or 35gr berger?

I want to make small creatures explode... like dynomite in a crows a**....

It appears from your responses to suggestions other than 1-12" that you'd already made up your mind. Why even ask for opinions?

 

[Ledd Slinger]

As was stated previously, RPM's will produce spectacular terminal ballistics. When my 8 1/2tw was new I pushed the 39 grain BlitzKings at 4123 fps and they would completely remove a chucks head when hit! When I got some mileage on it they stopped making it to the target.

Yeah that's a little fast, especially for that twist rate. I've had a 39gr BK come apart in a 204 Ruger barrel at 4100 fps when I was pushing the limits of my loads. And that was a 1 in 12" twist. The chronograph in front of my barrel was laid to rest that day

Had to slow the load down to the 3950-4000 fps range.

But hell, a 39gr BK at 3700 fps makes quite the explosive spectacle on small varmints. I've completely disintegrated ground squirrels with my old 204R load (and old barrel) running 3715 fps. Barrel life is really good at that speed too.