Grendel upper?

[YutYut]

I think some people choose a Grendel for the increased performance but then cripple the rifle be choosing too short of a barrel. The Grendel is not a handgun cartridge. The Grendel needs inches of barrel to burn all the powder. If powder is burned outside the barrel, you end up with a large amount of muzzle flash and lower velocity. If you want a rifle with a short barrel, one of the larger bore uppers (with are essentially a large pistol caliber) might be a better choice if you are going to cripple the rifle and only shoot inside 150-200 yards.

YMMV

i had the beowulf in mind. Whats the shortest barrel length that will give enough.time for the powder to burn up? Couldn't one use a faster burning powder to counteract this?