I have an mpa 45 carbine and its a ton of fun. The factory threading was some really weird spec that was more of a pipe thread so I had to have it re threaded for my suppressor. It is heavy but it's fairly accurate and runs well.
Very nice, now i just need to find a short AR57 upper to go on the pistol lower I just built using an Anderson lower and Spikes LPK I bought from there. They aren't horribly priced new but would like to find a used one.