Have not had a chance to fire it yet (weather) but another thread got me thinking. Man had a .58 cal. from someone other than GM that would not swallow .570 RBs. Anyone have any experience with GM barrels in this caliber? I have some .570 and .575 balls and two different thicknesses of patch material figuring that among the four variables I'll find a combination that works. Getting to the range from where I live is a production so I don't want to get there and find that I should have brought along a box of smaller RB's. As always, comments appreciated.