IMR4350 is what my bud has been using for the 139gr SSTs. But he is going to go up 168gr MKs or 162gr A-max's and we are thinking that a slower burning powder is going to be the ticket. After doing som more research last night and with the replies that I got here, we are going to give RL22 a try. we just need to figure out which of the two bullets are going to be used!!
Thanks for the help fellas. Being new to this sport, im sure you guys are going to see alot more questions from me.