long story short, a few weeks ago i got a AB-10 (last tec-9 version made by intratec) and have put close to 1000 rounds though it already and the only malfunction the gun has had was user error (my buddy didnt understand you simply let the bolt go when loading it)....ANYWAYS...I have really gotten on this "smg" kick and am currently looking at building a mac but have several questions...I have found cobray receivers already and plenty of different parts kits. my questions are..
-how do i know which part kit to buy?(am currently looking at parts kits from ftfindustries.com)
-can i get a m11/380 "upper" and use it and 380 mags in a 9mm cobray lower frame?
-can i use a open bolt fire bolt and parts kit in the cobray lower frame?
-what mag does the cobray lower frame use?

I have searched and read a lot, but still cannot find the answers to these questions, and the only way to learn is ask..  thanks for the help!

An M-11 .380 upper won't fit an M-11/9 receiver......it's about 2 inches too short.....

Can't use any of the open bolt FCG components.......manufacture of open bolt semi MACs has been prohibited since 1982..The only parts the SMG has in common with the semi are the magazines, bbl/upper, charging handle, front takedown pin, recoil spring assy, and bolt (the semi uses a different firing pin however)

It doesn't look like FTF sells a complete M-11/9 semi kit......which is what you would need to complete a finished receiver......buying individual parts you'd end up having about twice as much into it as a complete gun would cost..

A "stock" M-11/9 uses a single column/feed "Zytel" magazine......but there are aftermarket mags that fit that are much better choices (Shockwave "Z" mags / PAM-2 mags). Some receivers accept Sten mags.....but in all honesty, they are a worse mag choice....regardless of how cheap they are...they were popular during the AWB when you couldn't source affordable factory hi-cap mags

I love the challenge of a build, and satisfaction when it's done,  but by the time you add up your investment in parts/materials/labor, you'd probably be better off buying a used SWD or FMJ M-11/9 semi, or a used MPA.....




hope this helps.....

If you are building a semi m11/9mm, drop me a line if you need a complete upper and some mags. I have one that has been sitting around for 15 years that needs a home.