MP40 Feed Problems

[RKG]

Hello all. I've recently bought myself an agm mp40 but I've run into some trouble. At the moment only the metal magazine that came with the gun is feeding properly. Even the other metal magazines I have from my sten aren't feeding, let alone the king arms magazines. I have cut down the mag well but still the same problem.

I originally did the ak hop mod and thought that the problem, so I have put the original mp40 hop unit and barrel back but still having the same problem.

I'm not really sure what else to do, I had intended to use this gun at a Skirmish this Sunday but looks like I may not be able to.

Any help is appreciated.

EDIT: Just ran through the magazines with my sten and they all feed perfectly.