Hey guys! I just got everything figured out and it works perfectly now. The forum link 1952HRA posted helped me to locate the issue, although it wasn't exactly the same thing. The channel where the spring tang from the mag release lever slides down into the pin slot was very poorly machined out, and the tang was getting stuck in the channel. The rest of the machine work on the internals is impeccable, though. I got a file set from Walmart for somewhere around $3, and then filed the burrs and unmachined metal down, making the channel for the spring arm to slide down perfectly smooth. It works great now! One last question, if anyone is still looking at this thread. I got a Numrich 50rd drum, and I know you're supposed to grease them. I'll probably only use it very rarely (it's semi auto, and once you load the drum you've pretty much got to shoot all 50 rounds!), but I don't want to wear it out too quickly, as they're expensive. I'd like to avoid having to buy that $75 grease tool from the guy on here, does anyone know of a way to get some oil or grease into the area of the drum that needs it, without having to buy a grease gun, c clamp, and $75 nozzle cap?