keyhole issues HELP!!!

[havent got a clue]

Just got back from trying to get some GOP (glue on patch) to shoot. At 25 yds they were keyholeing. The paticulars are these; it is a .310 170gr gop LBT mold. I wrap the projectile exactly twice with a computer lable, size it to .309 with a push through sizing die, bell the case mouth and seat the projectile with very little if any crimp. I'm shooting them out of a 300 win. mag at approximatly 2700 fps.
I'm new at messing arround with paper patching but not new to bullet casting. Can one of you guys point me in the right direction?

Thanks

[Nobade]

I've never seen a GOP bullet, but if it works like a normal paper patch setup, keyholing is almost always a result of bullets too small. Don't worry about bore/groove dimensions. Size to fit the throat of the rifle. Make it just barely small enough to enter the throat. Then seat bullets to be a firm press into the rifling, at least 1/16". A loaded round chambered and removed should show rifling marks on the paper. Try this and see what happens. If it doesn't work we can explore other possibilities. 

[srussell]

can you patch them to .310/.311 and still chamber them. then slow them down to about 2500