I have noticed that Sierra jackets are a lot softer than J4s but Sierra only sells 1 length for each caliber which limits you in bullet weight unless you trim which is not that hard to do but just makes for 1 more process. The J4 is a little harder to swage the rebated boattail than Sierra. I haven't tried anealing J4s, maybe that would help. Need advice from all you pros on bullet swaging. Thanks Sledge