I bought a Browning Model 12-20ga from a guy on the web a few months back, and found that it would dump a shell out the bottom after firing a round. Apparently recoil would allow a shell in the magazine to get below the lifter/carrier. I took it to a local smith who replaced the magazine spring, which didn't fix the problem.
So, I took it back, and he ground on something till the shells stayed inside the gun like they were supposed to. I asked him about a stronger lifter/carrier spring, and he said there wasn't enough room there for a heftier spring.
I have shot a couple of boxes of shells through it since, and it seems to be working ok now.
Don't know if this is relevant to the thread, but thought I would add my experience.
Happy trails,
HHH
