Re: BL C(2) in the AR?
I have used H322 with great results with a 55 gr FMJ. H322 is small kernal and flows very well, burns clean, and gave the best velocity from everything from a HK53 with an 8.5 in Bbl to a 20 in A2 Bbl. Only takes around 23 grains or so. I do not have or remember the charge right now. A side note, it cycled the HK the smoothest of all the other loads I tried or any fatory/surplus ammo. You have to be careful with the roller locked guns as they require quite specific loads for the locking piece they have. The 53 especially. But if you tune the loads and bullet weights to the locking piece, or vice versa, you will love it. H322 Runs really smooth in AR's too.
So yeah, H322 gets my vote. Its an Extreme powder too, so it should be fairley temp stable. Which is good to have if your rifle ends up liking the load on the edge. And you save about 4 grains a charge, so the price is a wash when compared to loaded rounds vs price per pound. Blc2 is usally a little cheaper.