Not grendel, not sure what it is? Need some help.

[jcjarmon]

I found a barrel today that peaked my interest. The only markings are stamped on the barrel twice, "300 FB". The barrel is exactly 16 inches long, Carbon fiber wrapped, before and after the gas block, non-threaded muzzle, .125 gas port, and carbine length gas system. It appears to have had a A2 style gas block on it at some point. The muzzle measures .300 by a caliber. I figure the 300 fb, is for 300 fireball. But the barrel appears to be carbon fiber wrapped 4150, not stainless. Who made a Carbon fiber wrapped barrel in 300 fireball?

[Old Bob]

Yup, it's probably a 300 Fireball which is basically the same as 300 Whisper (also called 300/221). They are both formed from 221 Fireball parent cases & 35mm long. 300 Blackout ammo might fit in that chamber as well but the Blackout brass might be too thick at the neck & cause pressure problems. Alas, I couldn't find anyone who makes carbon fiber wrapped 300 FB Barrels now-days. That chambering might have been phased out in favor of the Blackout. You might contact Proof Research, Christensen Arms, Carbon Six or BSF Barrels & ask if it's one of theirs.