I'm a Sierra guy....never used a Hornady in that weight.
IMR4895 works very well in match tuned gas guns but Varget seems to be the latest rage for the M1A guys.
I've had good results with H4895 in a Savage bolt gun but much prefered IMR4895 in the .308 Garand that I used in matches one year.
I'm a big believer in Federal Match Primers. In fact, I use them exclusively...even in my 30-30 hunting loads.
Can't help with an exact load. That'll vary by action type, chamber/throat deminsions, AOL requirements, gas port location, and/or other factors.
A good place to start would be to get ahold of one of the Techs at Seirra, give them as much info about your gun as you can and get their input. They'll be glad to help and don't care who's bullet you are using.
You can e-mail 'em or call. They stay busy though, so you gotta be perty-lucky to get one on the phone your first couple of tries.
Either way, their contact info is on their website.
Hope this helps.
DGW