Mine seems to like just about everything I've tried so far. Most of my loads have been with the Speer 80 spitzer. I have done a little work with the 70 and 85 grain sierra hps and the Hornady 87 grain spitzer.
I went back and reread Sam Fadala's write up on the 6mmx222 and he got some impressive velocities from the little cartridge. I don't know how he got 27 grains of BL-C2 and an 80 grain bullet in that case but the article says he did. It must have been heavily compressed or the Speer cases he used had greater capacity than the Sako, LC 83, Winchester, Remington and Frontier cases I've checked. The Frontier has the most room and 27 grains comes to 1/8" from the case mouth. Remington is the next most spacious case and the other three are all within a 1-2 grains of each other and 27 grains of BL-C2 fills them to the top of the mouth.
I loaded up some more test loads with H322, Benchmark, 3031 and BL-C2 and the Speer 80 grain. I'll hit the range Thursday for one more session before I head to the slope for my work hitch.
