Anywhere between 50-53grs of RL-15 with the Barnes 210 TTSX all shot sub-MOA for me out to 600yds. I settled on 51.8grs @ 2660fps
so I could match the drop in my Shepherd P2 scope. 53grs put me @ 2920fps so work up carefully.

Hope this helps,
johnny

No Farmers---No Food