I don't have a GPH but know several that do,and spent just yesterday shooting alongside several at an open-house/rendezvous. Projectiles were as varied as the shooters. 1 feller was using Buffalo Ball-et,2 using powerbelts(1 using H.P.the other soild) both did not like the powerbelt aero-tip. These 3 shooters were using tween 75-80grs of 2f Goex and fine shooters all. I know another feller shoot's nothing but Lee REAL 380grs on top of 90grs 2f.(shooting solid lead is all about the lube!) he get's 2" groups at 100 using peep's off a bench! These are all .54 GPH.
It won't shoot ball well,,much past 50,,too fast a twist.
I shoot a 1-48 twist and have found a prb load I'm content with, I've tried many of the bullets and have plenty around I'll not use, there's a dozen Buf.Ball-et left,I could toss in a few REAL 300grs and 4 Lee Improved Minnies for ya to experiment with if ya wanna re-imburse me shipping cost. I gotta go to town tommorrow and I'll check the weight and cost.
Let me know if yer interested and we'll PM addies