Range Day and took out a few rifles. One was a PSA 9mm carbine. I picked this up about 6 months ago used and have only put a few mags through it, but never had an issue. Yesterday I have two cases blow apart. First one was while I was using regular ball ammo in brass case. Didn't really notice anything until I saw the deformed case on the ground. Loaded up a mag of silver bear 9mm and after 8 - 9 rounds there was a boom and the Glock mag came out of gun and lots of smoke. Can't really see anything wrong, but this time stopped firing and will call PSA in the AM and send it back for review. Never seen anything like this before.

Looks like an OOB.
Bolt bounce from too light a buffer can cause this.
What is it running for a buffer system?

I have a PSA colt pattern lower with all KAK BCG/buffer/barrel and had an OOB on a 147gr. Clear signs of the flat nose setting off the primer of the case ahead.

You look to have a bulged primer on one case.

I had a PSA 9mm carbine. It did the exact same thing that yours just did. It also had a nasty habit of doubling. It did these things with several different varieties of ammo (factory and reloads), different buffers, different springs, and different trigger groups. I finally gave up on it and traded it off with full disclosure at a huge loss.

I recently replaced it with a new build that I did on a standard lower (uses the endomag pmag conversions) with a CMMG radially-delayed blowback 9mm barrel and bolt combo. I've got close to 1,000 rounds though the new gun, and not only has it actually been reliable, but it operates much more smoothly than the straight-blowback PSA. No more straight-blowback guns for me.

CMMG hit a home run with the radial delayed blowback system...my 9MM Banshee upper has been flawless and much smoother with less recoil than the straight blowback actions...you made a good choice ...and ain’t those CMMG MagPull 9MM inserts slick!

quote:

Originally posted by Bisleyblackhawk:
CMMG hit a home run with the radial delayed blowback system...my 9MM Banshee upper has been flawless and much smoother with less recoil than the straight blowback actions...you made a good choice ...and ain’t those CMMG MagPull 9MM inserts slick!

Indeed they did! And yeah, the pmag inserts are awesome. I was skeptical when I first saw them, but they have been flawless, and the ability to use them in a standard lower is really cool. It opens up all kinds of possibilities (like SBRing the lower and sharing it between rifles) that a dedicated lower doesn't offer, not to mention they give you LRBHO which the PSA Glock mag lower (and many other 9mm lowers) don't.

The smoothness is also pretty amazing compared to the blowback guns. I was originally looking at MPXs and the PTR 9CT as a replacement for the PSA, but I just couldn't bring myself to justify $1800-$2000 for what is essentially a range toy. I built the CMMG for right around $700, and I actually like it better than my buddy's MPX. It's just as smooth, lighter, and slimmer. Add to that that it's not rupturing brass in my face or turning itself into a machine gun all on it's own without warning, and it's been a huge improvement over my PSA blowback carbine.

I traded the PSA along with another gun and some cash towards a brand new Marlin 1894C in .45 Colt...a gun I'd been wanting for quite some time. On paper I got a horrible deal....but I was almost as excited about being rid of that PSA as I was about getting that new levergun, that's how bad it was.

I have contacted PSA and waiting for shipping label. The rest of the silver bear case fell out of the chamber, but I checked the barrel and there is a bullet still in the middle of the barrel.

I believe the factory PSA 9mm buffer is 5.5 oz, which is pretty light for that application.
I used a PSA 9mm upper and for the recoil system I started with a Carbine tube, Rifle spring and a Vltor A5H4 (6.8 oz) buffer.

It functioned flawless with Endomags but was smashing the case mouth flat and flinging brass to the the next zip code.
After installing a Law folder and the 2 oz adapter it brought the total mass to 21.5 oz and stopped doing that.

From everything I have read on 9mm blowback systems a 9 oz buffer is is about the ideal weight.
Or a total mass of 21 - 23 oz.
And that makes it punchy.

So now to fix that I'm saving my pennies again and getting a CMMG 8" barrel and bolt with the mag inserts.
That'll shave 6 oz off of the buffer and CMMG has a bolt tuning kit to dial it in.

When I was looking at building a 9mm AR I was overwhelmed with all the options/different systems available, looking at the advantages of each system ... I have a buddy going through that now. Not being able to find a finished lower he bought an 80% 9mm Glock mag lower, but he has access to a mill so it should be a breeze.

As for me, I finally settled on a Colt 10" SMG upper/demilled kit I found on GunBroker that came with the upper, bolt carrier, receiver extension, spring and buffer even the +3-rnd burst trigger, magwell block, 2 Colt Mags ... everything except the receiver.
Over the last couple years I've seen the problems of others and have been glad I went that way.

If anyone would like to know, I can weigh my Colt buffer and post it here ...

Although a dedicated 9mm lower and Glock mags would be nice, but now I've got a dozen or so 32(?) round mags and I don't see getting a didicated lower and having to either make a pistol or sbr.

BTW, it's my 2nd favorite 9mm PCC, right after my MP5 clone!

quote:

Originally posted by 92fstech:
I had a PSA 9mm carbine. It did the exact same thing that yours just did. It also had a nasty habit of doubling. It did these things with several different varieties of ammo (factory and reloads), different buffers, different springs, and different trigger groups. I finally gave up on it and traded it off with full disclosure at a huge loss.

I recently replaced it with a new build that I did on a standard lower (uses the endomag pmag conversions) with a CMMG radially-delayed blowback 9mm barrel and bolt combo. I've got close to 1,000 rounds though the new gun, and not only has it actually been reliable, but it operates much more smoothly than the straight-blowback PSA. No more straight-blowback guns for me.

Very interested.

Is the CMMG RDB upper & bolt combo available without the barrel, would you know, please?

Would be interested in just replacing that portion of my AR9... probably not an economical way to go, but the benefits are very attractive.

quote:

Originally posted by ersatzknarf:
Is the CMMG RDB upper & bolt combo available without the barrel, would you know, please?

Would be interested in just replacing that portion of my AR9... probably not an economical way to go, but the benefits are very attractive.

Won't work on a blowback barrel, RDB has lugs that go into a m4 like feed ramp

quote:

Is the CMMG RDB upper & bolt combo available without the barrel, would you know, please?

Like Candyman said, you'd have to replace both your bolt and your barrel since the lugs for the RDB system that interface with the bolt lugs are built into the barrel extension very similarly to a standard DI AR (they're just angle cut rather than flat to allow the bolt to rotate under recoil without the need for a gas system). You could, however, keep your existing upper receiver. CMMG sells their RDB setup as complete rifles, uppers, or as bolt and barrel combos, which is the route I went.

Here’s the barrel and BCG...the only thing the description is that the upper requires an enlarged ejection port...I guess the hand guard of your choice would depend on what barrel nut you use to build your upper.

https://cmmginc.com/product/ba...it-8-4140cm-sbn-9mm/

This is the upper I bought (it was about $90 cheaper when I ordered it through Bud’s earlier this year)...

https://cmmginc.com/product/up...mkgs-9mm-2-30rd-mag/

quote:

Originally posted by Bisleyblackhawk:
Here’s the barrel and BCG...the only thing the description is that the upper requires an enlarged ejection port...I guess the hand guard of your choice would depend on you use to build your upper.

https://cmmginc.com/product/ba...it-8-4140cm-sbn-9mm/

You're right...I forgot about the enlarged ejection port. I used an Aero XL upper for my build.

Many thanks to everyone for your replies.

Understood. Need the barrel as well.

Hopefully the ejection port already on the rifle is large enough, but if it's a kit with upper assembly and barrel, then that's likely not a concern?

If it's possible to do just a bolt and barrel combo, that sounds most economical.

This: https://cmmginc.com/product/ba...t-16-4140cm-sbn-9mm/

However, need one for a Colt pattern lower (DDLS).

This message has been edited. Last edited by: ersatzknarf,

When I was researching my build, some guys said that they ran them on uppers with a standard ejection port and it worked fine. CMMG recommends an enlarged port, though, and I needed a new upper for my build anyway, so I bought an Aero XL. I imagine that if you were to purchase a complete upper from CMMG, you could safely assume they're using an upper receiver with an enlarged port.

Mine seems to be fine with ejection...no problems ...But it’s a complete CMMG barreled upper.

Thank you both.

Sent an email to them, a few days ago, but now have a better idea of what to look for, thanks

Have the build sheet somewhere and that might help.

At least now there is a direction in which to go.

Embarrassing, but not having the best of luck navigating their website...

Thanks, again!


ETA: found it!

Upper is Vltor MUR 1S with no forward assist. The lower is a VGN-T1 Colt pattern.

Good luck with your build! A good 9mm carbine is a blast to shoot...incredibly handy and controllable.

Thank you very much!

It's already a nice rifle, from the builder.

The buffer seems to be taking a bit of a beating, it seems. Hence the interest in the RDB.

It is a lot of fun and very controllable.

It's been called a tack driver by friends.