Have a SBR AR in .223.  Been wanting to build or buy 9mm upper for it for occasional use.  It will usually be suppressed.

Tempted by CMMG's radial blowback design.  Their website shows a Banshee 300 MkGs upper that comes with  3, 30 round  AR style mags. Challenge is it's $850 at CMMG's website and they say there is at least a 20 week shipping delay. Ugh.

I am able to find CMMG radial bolts online, but they say they are designed to run using Glock mags, AND that you need an enlarged ejection port. Is also need 9mm AR barrel but I don't think that's too hard to find.

Third option seems to be to buy Glock Magwell insert and just buy Glock compatible 9mm bolt and any 9mm barrel for typical straight blowback approach.  

Not sure I'm understanding all the ins and outs on a 9mm upper solution.

Your options are...

Buy/build regular blow back upper with endomag compatible BCG and use your lower with a endomag conversion.

Buy/build CMMG RDS bolt/barrel assembly, build your own upper assembly, and use CMMG compatible endomags for the CMMG RDS  BCG and use your lower.

Buy a complete CMMG upper for use with endomags and use your lower.

Buy/built complete 9mm upper (either blow-back or CMMG RDS) and buy mag insert for whatever mag style you want (glock/colt)

And for a suppressed blow-back, contact Rudy @ Macon Armory for upper build options/advice

At this point, your on your own for what might  actually be in-stock in the next few months, or what you can buy on the EE

Good luck with your project.

Bear in mind that the CMMG RDB bolts require their proprietary carriers that have a special cam pin path.   The barrels also are not like a blowback 9mm AR barrel.
The CMMG barrels have an extension on them just like a 5.56 barrel.  
I had a custom 9mm RDB barrel made with stainless barrel by DeadShot barrels and also a .45ACP RDB barrel made by Rudy at Macon Armory.
Picture of the breech of my 9mm RDB barrel.
More details on my site here: http://www.c3junkie.com/?page_id=164

Attached File


The only source I know of for the proprietary carrier is CMMG which I don't think is available separately so you might as well get a BBL/BCG combo as a minimum.

I ordered a Banshee 300 9mm upper in September.  It's finally in production now.  I already have some mag conversions set up to use with one of our M16 lowers.
My Banshee 300 lower is still not in production yet.

I added a CMMG radial delayed barrel and bolt to a Glock format AR9 previously built as a blow back...by not using CMMG's lower, I encountered clearance problems with the magazines...I would not suggest the RDB unless you plan on building a competition carbine.... my SBR has both a .22lr and 9mm upper... I used the magazine block by Macon Armory as the Endomags were not available at that time, so my 9mmSBR uses Colt  magazines... I would suggest you go with the straight blow back, and if the Endomags work as well as most say, give them a try first   regards

Look into the buffer due to bolt assemblies length differences as compared to 223 and travel.
The AR9 is recommended with a longer than std AR9 buffer (FM-( Buffer) or use a Spike 9mm Buffer block (about 7/8") with a standard 9mm buffer.