I had a misunderstanding with a while back about getting rid of a big bore. But rectified the issue. As for the big bore a .457 tx2 lss with medium spring tune and a polished barrel. I got 5 shots in when I installed the spring on lightest tension. I shot a 340 grain solid flat nose past a chrony set at roughly 25 feet and of those 5 shots the best one was 984fps. At some point I will post a chrony video with the highest fps with what ever grain weight I have most likely 340 grain. The mold for the 340 grain flat nose is double mold lee. 458 I do have a 457 sizer but no problems unsized.