I posted this over in the pistol caliber carbines section and got zero replies.  Perhaps somebody over here can lead me in the right direction.  I'm looking to get a Quarter Circle 10 Glock lower for a 40 S&W build. Which buffer do you guys think would work best for this? Looks like RRA's LAR-40 uses an H-2; is that the way to go?  Also, a standard stripped upper is meant to be used on these, correct?  
Thanks for the help.

I use a 45 buffer from Heavy Buffers, mine works great with it, I have a 9MM upper and it works fine with it. I also have the Wolf heavy buffer spring.

A regular upper works fine. I used one of these since I didn't need the bolt assist.

http://www.blacksheep6tactical.com/

Aero Precision also makes a similar one.

Don't have an answer for you but have been very interested in a 40 cal but in a 10.5 inch barrel / sig brace set up. Can you post pics and specs of your build when your done?

Thanks, I saw Slash's buffers but was hoping I could find a cheaper alternative.  I may have to go this way unless I get enough people saying something else will work.

I will eventually post pics on here but it will be a while before it is complete.  I plan to use the QC10 lower, 5.5" barrel (or whatever similar length they come out with), and bolt, Bravo Sopmod stock, AAC Ti-Rant .45 suppressor, 13" Seekins BAR rail (as long as the suppressor will stick out a little, which it should) or else the 12" bar or MI quadrail.  Of course this is all a few thousand dollars away and will probably change between now and when its done.  Heck, a couple weeks ago I thought my next build would be 300 blackout, so who knows.

I also have a 300 blk SBR with suppressor and it is one of my favorite guns to shoot. It has a push for recoil rather than a snap.