Has anyone used this caliber yet? I re-barreled one of my uppers to a 16" 221/300 and was pleasantly surprised! I use 221 fireball cases necked up using the Redding 221/200 die set. So far, I've only used H110 powder and CCI small rifle primers. I get great results with 125 grain ballistic tips and 200 grain Sierra Matchkings. The in-between weights don't offer any improvement over these two extremes for me. I zero at 200 yards and get a close enough trajectory (with the 125 gr ballistic tip) to use a scope with a .223 range compensator. Accuracy is awesome, <1 MOA. I bought the barrel from Model-1 sales and I have no idea who made it, but it chambers well, even with fireformed cases and functions flawlessly with a standard AR mag.
My two favorite loads are:
125 grain Nosler Ballistic tip
CCI400 primer
H110 powder - 20.5 gr
OAL - 2.1"
5 shots
H - 2320
L - 2285
200 gr Sierra Matchking
CCI400 primer
H110 powder - 10.0 gr.
OAL - 2.4"
5 shots
H - 1076
L - 1035
Has anyone worked up other loads?