So I have a no4 rifle I had built up a few years ago from an old rifle. The barrel was worn out and the stock was so rotted and loose that no amount of oiling could bring it back to life. I had it built into a faux-T thru a collaboration by Brian Dickicon and Bruce Dow and it turned out great.

The only problem is the magazine has never fed reliably or well. If I put one round in the magazine, maybe two or three, it’ll feed ok. But anything more and and the round just gets ends up slamming into the feed ramp and stopping. At best, sometimes the bolt might glide over the round without pushing it forward at all. I know the magazines were fit to each individual rifle but I don’t know how to do this or really even where to start with diagnosing what precisely the problem with the magazine is.
Was hoping someone could point me in a good direction.