When I had a B52 I found that the shells wouldn't feed through the magazine unless the bullets were seated completely flush with the brass. If the bullets stuck out at all, they were too long.

I have never gotten a plated bullet (Ranier, Berry's, etc.) to shoot worth a damn out of any gun.

I used to shoot mine in PPC, so modified the mags to hold 6 rounds. You do this by extending the slots on the side of the magazine 3/8" further down. The slots are angled, but the extensions need to be straight down, parallel to the front and back of the magazine. If you follow the original slot, the follower will bind up. The magazines (like most) are tempered spring steel. You will need a carbide end mill to cut them. Use a slow RPM, 300 - 500 to keep from overheating things.