Re: Favorite load for 55 grain 5.56mm round
Not a favorite load, but a load that works reasonably well - straight out of Sierra's manual. Rem 7.5 primer + 21.5 grains of Reloader 7 + 55 gr FMJBT gets you about 2,900 fps in a standard 16 inch (carbine length) M4. This is a <span style="font-weight: bold">max</span> load. RE7 meters reasonably well, at worst +/- 0.2 grain in a Harrell's powder measure, but is not a terribly efficient powder. ETA: 2.25 inch COAL.
A lot of folks seem to like 24.5 grains of Ramshot TAC (not a max load). I recently chatted with some technicians at Sierra about their 55 gr load preferences and this powder came up more than once. I'm gonna give it a shot this weekend.