Mike:
What kind of velocity did you get from the 560s? I assume you know. If you don't, you're poking around in the dark.
Eight inches wide at 50 is a lot. If the vel of the 560s was reasonably close to the ballpark, yeah, you obviously need a lighter bullet. You might not be able to go light enough to cure it either. I ran into two in a row that shot 6 to 8 inches wide at 50, and I couldn't drive even much lighter bullets fast enough at sane pressures to cure it. Both had to be re-regulated.
Hawk will make a custom order with thin jackets that I don't think will harm the barrels. Might be worth a try.
