My .54 GPR blows patches also, I used J&B bore paste, fired it and cleaned it a bunch, and it still blew patches. So I gave up and started using wonderwads, and it now shoots great, cloverleafs at 50, 4" at 100 (off the bench) with 100 grs FFg, .018 pillow ticking lubed with mink oil, a .530...