Hola,
I have a PSA PX-9, AR9 9mm pistol that is set for Glock mags. PSA does not make a .40 upper and that is what I am looking for. Does anyone know of an upper that will work with the PSA lower?
First question would be does that lower accept .40 cal glock magazines ? I know a .45acp glock pattern lower is supposed to accept 10mm glock magazines. I have that same PSA 9mm lower but only 9mm mags for it.
I do need to get a 10mm mag so I can validate that my .45acp lower accepts them for a 10mm upper. Ugh…then I need to look at .357sig. Again I suspect the .40cal magazine is a profile closer to that of a 9mm. It goes back to the frame/grip size of the glocks to my best knowledge.
Build your own. I did. Regular Aero AR15 upper, Kaw Valley barrel, Kaw valley BCG
Glock 40, and 9 mags have the same outside dimensions.
NQNPIII,
Does your Aero upper work on a PSA lower?
I got in a discussion with a guy the other day. My PSA lower fed 40 into the Aero upper when using the chargin handle. The lower I built for that is a Matrix Aerospace. I put the Matrix on my PSA 9mm upper and it fed a round in the chamber just fine.
Got my barrel, BCG, and forward facing muzzle tip from Joe Bob’s. Cut a feed ramp into the barrel with a Dremel and polished it.
PSA’s upper is a regular AR15 upper. Compare.
I will compare my PSA upper and lower to one of my AR’s. If it is the same I will just build the upper (Joe Bob’s has the best prices I have found) for now.
Thanks for the heads up. Any other advice on this build would be appreciated as well.
Don’t use the New Frontier BCG unless you want to mod it. I put a Matrix Aero floating 13.5" guard on mine. For historical foot note I actually built a 16" upper.
I have had it out 3 times so far. Changed the BCG to KV. It seemed to run good with a 3.0 regular AR buffer. Last trip out I used a Spikes 5.2 (T3) buffer. Out of 150-ish rounds I had 2 jams. Purple Winchester government practice ammo, and some 165gr JHP Ranger bonded. Nose up jams. One with each type. I should have taken a 3.0 with me.
I just checked and the PSA upper on my PX-9 is just a regular AR upper but with a 9mm barrel. I am ready to build a .40 upper now.
I took it on my own to notch the upper. Left and right is some U notches to go to the M4 feed ramps. Glock mags feed from the center I cut a notch in the center to the same depth. I’m not sure it helps. Don’t think it hurt.
I have a PSA lower (Glock Magazines) that works fine with an upper I built using KVP 40 S&W barrel. These barrels are on sale at Job Bob Outfitters for $80 right now. I mounted it in a $40 slick side Anderson upper and used a $45 Double Star Carbine length float tube.
Utterly reliable using the KVP 40 BCG from Joe Bob’s though I always polish the feed cone on Blow Back barrels prior to installation.
If you don’t want to build an upper then Stern Defense would be my choice. There BCG should work even better because it is an ounce heavier than the KVP BCG. I added the KAK tungsten weight to my KVP BCG which brings the weight up to 16.5oz and helps mitigate recoil.
Ive shot three different barrels using a QC10 lower, new frontier, gorilla machining and Faxon……….I did have the feed cone worked on by Macon Armory, but have not shot any hollow points in it…the new frontier barrel works fine with hollow points and the gorilla machining barrel has only seen ball……….
Very nice!
I see the CMMG Guard is now available in 40 S&W. I just built an upper in Blow Back 40 S&W but can’t wait to try the Guard. I’m enjoying my Guard 45 ACP and 9mm.
You have an appetite for the high dollar stuff! 
https://www.cmmginc.com/?s=40+s%26w&post_type=product
I also have and enjoy my MKG 45 Guard and my 9mm MKGS Banshee. I’m planning on getting a 40 S&W upper when they become available. I’m glad that since the 40 S&W is threaded .578-28 the same as the 45ACP,I’ll be able to use my AAC TiRant 45 on it without a thread adapter.
bbbbbbuuuuubbbbbbutttt .40 is a dying caliber! LOL!
They are expensive but so much softer shooting.
My 45 ACP blow back is a tack driver but quite snappy in the recoil department. I running it in an A2 stock with just over 16oz of buffer weight and the Tubb’s 308 spring and recoil is snappy to say the least. My 45 ACP Guard is a much gentler in comparison.
I’m running the 3.4 oz weight from the CMMG Action Tuning Kit .
That is the beauty of the Guard system, it doesn’t require the weight of straight blow back guns. I’m doing pretty much the same as you, no extra weight anywhere in my 9mm Guard but went with an H3 buffer and the Tubb’s 308 spring in the 45 Guard. If you have never tried the Tubb’s spring it is amazing how much it smooths the recoil impulse.