I initially had no desire to do a .45 ACP CMMG RDB setup because:

  1. I didn’t want to bother messing with trying to get it to work with a standard lower as the current mag options are maxed out at about 20 round capacity (Macon Armory proprietary mags or the USC mags).
  2. I didn’t want to get another Glock lower just for this.
  3. I no longer had my MGI Grease Gun magwell to use unmodified GG mags.

I happened to run across another MGI GG magwell so I decided to do a .45. 

After all the issues I’ve had with the ejector springs dying in my 9mm and .40SW, I thought I would start out with a custom barrel with minimal headspacing slop.  Although I will say that I haven’t seen any reports of ejection spring failures in .45ACP.  Neither have any of my friends running the .45 RDB in full auto….but I don’t think any of them shoot the .45’s a lot.

Regardless, I decided to get a custom barrel made out of SS.  Stainless because it would be easier to deal with if I wanted to port the barrel for an integrally suppressed upper.

So I purchased the Wilson Arms SS .45 ACP blowback barrel on sale for $80.  

I purchased a 40/45 3 lug adapter from Griffin Armament.  Just the CMMG .45 ACP BCG ‘repair kit’ to primarily get the bolt only.

I also just got a standard M4 extension and sent it all to Rudy at  https://maconarmory.com/

This is what I got back:

I’m using my preferred buffer tube, buffer and spring setup I use in the 9mm CMMG RDB which is:

Vltor A5 buffer tube (or equivalent length buffer tube)
Kynshot RB5007
556 Tubb Flat spring

Old Gemtech Blackside .45 ACP suppressor used with custom adapter made by Curtis Tactical to use the Grffin 3 lug mount.  Interestingly, there is almost no change in the cyclic rate when suppressed while I see about a 60 RPM increase in 9mm.

I also tried some old 200Gr SWC profiled reloads and it ran those pretty well also.