I only know of one place to get complete 9mm colt style rifles....ASA (oh and colt but thats LE only)Anyway.....Lets take this slowly ok?
1.Youll need an upper assy.,RRA and ASA (and colt if youve got a preban lower)and a couple others i cant remember make uppers...I went with RRA, If your on a budget then get an A2 upper so you dont have to buy optics,And shop around, RRA A2 uppers are 450$ on there site but you can find them cheaper.....
2.you need a mag adapter...There are several options here,,RRA..goes in from the bottom,,ASA goes in from the top....Both are 1 piece but the RRA retains the hold open feature(only if you use Colt mags$$$$$)also there are several 2 piece blocks out there...All these use Colt mags$$$ or modded Uzi mags(mag catch and rear notch cut)..The "new uzi block" uses stock uzi mags but im not sure off the status of this one..Also theres plans floating around to use modded sten mags and a 2 piece block, but this might be a little too much for a first time build
3.9mm buffer and CAR recoil spring.....If you use the A2 stock,fixed car or M4 stock,or Ace stock youll need the 9mm spacer also..
4.Uzi mags....25 rounders go for 10$ or so 32 roundrs like 20$ and up...And someone to cut the mag catch and notch....Factory colt mags..$$$$$$ but retain the hold open feature..
5.9mm hammer...Only like a 8$ item....Or if you please you can have your 9mm bolt ramped for 70$ by JoeBlack and use the stock hammer and ease the stress on your lower(Shameless plug No.3 Joe LOL).....
Everything else is stock AR stuff,,,Lower,lower kit etc.etc.etc.
9mm carbines make excellent 75yard and less rifles and are suprisingly accurate,Recoil is like 75% of milspec 5.56 stuff,Downsides?...They are Blowback operated so they are DIRTY! and it seems everyone who builds one has problems at first..but with help from the boards debugging is not a problem.....Anyway hope i dont confuse you more And im sure if anything i said is wrong or if they want to add anything someone will chime in,And as allways YMMV...........UNDERDOG