Once in lifetime for a tag??? Holy crap that sucks. [:'(]Where I hunt weget a bull tag for every 2-3 guys. You might not get the tag but at least one in your group will get one and anyone can shoot the bull. Cow tags are a different story all-together. Good luck getting them without lots of guy's in your gang.
I'm not sure what my max load is for my GPR. I'd have to check my manual when I get home. I would imagine that it would be around 100-110 gr 2f. That would do it, but I would think you definately want to keep the shot under 75 yds. I think I would also carry my BLR 300 win mag as a back up for the longer stuff.