Anyone do a PCC in .40s&w? What barrel and bolt are you using? Any issues you have run into?

I'm running the CMMG RDB in 9mm and .40SW.
.40SW setup pictured below.  Using the CMMG Glock lower, CMMG RDB BBL/BCG combo and the rest are parts I had laying around.  Upper is an Aero XL.


I'm running this with a RDIAS in full auto.  I've had the dreaded ejector spring failure in this setup at around 900 rounds with the original spring.  CMMG sent me their new MK10 ejector spring used in their 10mm and I'm at around 700 rounds now with no issues.  I'll be happy if it makes it past 3000 or so with no ejector spring failure but haven't gotten that far yet.

I've got a QC10 .40. QC10 lower receiver, bolt and barrel.  It has worked perfect from the first shot.  Have about 1500 rounds through it.

I need a 40 RDB in my life

I did this, since one of my AR9 carbines in built on a Glock-compatible lower.

I picked up an 8.5" Kaw Valley Precision .40S&W barrel from JobBob's Outfitters, along with a New Frontier Amory .40 Bolt Carrier Group. I also swapped out the Spikes ST-9X 7.7oz buffer for a heavier 8.4oz one to counteract the extra umph of the .40. I decided on a regular A2-style flash hider, rather than one of many linear comps. I paired it with a generic carbine-length free-float tube, a set of HK sights, and a Primary Arms red dot.

I tried it with 165gr WWB and Federal 180gr. The Federal is a little longer and has a more rounded ogive, and feeds flawlessly.  The shorter/flatter 165gr WWB started to hiccup.  That stubby round is making quite a jump into the barrel.

I used the Federal to sight the red dot in, POA at 25 yards. What surprised me was how easy it was, once sighted-in at 25 yards, to consistently ring the 18" gong at 100 yards. Pretty much POA/POI.

It's really fun to shoot. I like how it runs on the 180gr, and the .40S&W really thumps the falling steel plates on the range. I'll try and get a picture up of the setup.

I recommend trying it, especially if you have one of the Glock-compatible lower

I wouldn't mind a 40 upper to go with my dedicated Colt style lower. The problem is finding Colt style magazines for 40 S&W. Yes 40 will fit in the 9mm magazines but I don't like how they stack and wonder if they would even feed reliably.

Bought a Oly K40GL back in the day, and it's run like clockwork all these years later.

It was kinda funny to see that it made the Canadian Ban List, among the 1500 others.....

Almost all QC10 parts.   Runs well.   Love it.