I shot a couple matches with Blackhills (77gr Sierra) It was prolly 1996. I won one of the matches, I liked them. After that I switched from reloading 69s to 77s.
Other than 2 boxes of Blackhills everything I've shot has been a reload of my own.
Of those I've used
69grn Sierra Matchking, (they shoot fine with multiple powder primer combos.
77grn Sierra Matchking, This is what almost all Highpower shooters use fro 2-300 yards. Loaded to just fit in the magazine, they shoot great with a variety of powders from AA.2520, Hodgen H 380, Varget, IMR 4995, Vhitavouri N140, Any Primer but Federal, as those are soft.
Hornady 68grn Match (They were so-so) Can't remember if I tried 75gr Hornadys or not. Overal I judge their match bullets less consistent to Sierra.
60grn Nosler Ballistic tip, (Great for Coyotes)
60gran Sierra FB Hollowpoint, Good on Hogs up close, or placed shots out to 150. They sometimes punch through Coyotes, Hence the nudge to Nosler for them.
That's it. I personally wouldn't buy 55grn anything anymore unless I was buying those whitebox winchers rounds with the 45grn bullets. Those where good for whacking crows.
A good barrel will shoot most any of the above rounds really well.
My experience is if I get a barrel that feels like its finicky about the load, I'll chunk it and get one I don't have to dick with for it to shoot good.
Don't know if this helps too much in your case, but that's all I got.
24.5grs of any of those powders is about the standard charge for rifle length barrels.
And By Far Vhitavouri is the cleanest burning of all those powder bar none. A consideration I feel for gas guns and suppressors.
WhiteOak has a reload page with loads Ol what's his name uses.
http://precision.whiteoakarmament.com/info-reloading.html
And He kicks Ass. (mind you he's not loading for velocity only for the accuracy he's looking for)
Champions Choice has few different brands of ammo, not sure if price is best:
http://www.champchoice.com/store/Main.aspx?p=CategoryBody&c=APRCCH