[Clint N. Suhks]

I’m sure it’s all physics I’ve not researched.

I should do that. Owning a Ferrari doesn’t mean I know how to use one.

[smokingfrog]

The original M-16 started out with a lighter bullet and slow twist rate. They use heavier bullets with a steel core now for better penetration, which requires a faster twist rate.

http://firearmshistory.blogspot.com/2011/05/history-and-development-of-assault.html?m=1

4 legged varmints don’t wear body armor, so we can use lighter/faster bullets/cartridges.