Do you get bulged brass from your Megastar? Even with a moderate load, 180 FMJ over 8.7gr Longshot, I still get a slight bulge at the base. It appears to be where the feed ramp extends ever so slightly into the chamber. I have put about 200 rounds through it without a malfunction but this bulging of the brass annoys the heck out of me. Is it possible it is opening too soon? Maybe a stronger recoil spring would help if one could be found. The recoil spring in it is probably the original one. Wolfe doesn't make springs for this gun and I haven't found any place that has parts in stock.
I wish I could help you. Sold my NIB Starvel model awhile back.
Always wondered how it would shoot. With all that mass I'm guessing recoil is pretty mild.