I had issues with two BX 25's. One they would not easily snap in place or come out of a 70's era 10-22 There were dimensional differences between them and the the original 10 round mag. A file solved that issue. The 2nd issue was a failure to feed especially with the first 5 or so rounds of a full mag. There wasn't enough up angle of the bullet and it it would jam against the bottom edge of the chamber, again filing a steeper angle on the follower solved the problem and they run find now. Your results may be different.
the BX-50 is actually the BX-25x2, it is essentially two BX-25 magazines molded into one. So you shoot 25, drop the mag and flip it, re-insert mag and shoot 25 more. I have 2 of them and they work well. Like buttanic said, sometimes if I load them with the full 25 it will jam on the 1st or 2nd round, I experimented by loading 23 rounds instead of 25 and have never had a problem. I guess I could file the follower but I'm too lazy to do it! hahaha