9mm blow up

[popper]

Original AK had that problem, they put a spring on the FP (US imports) to solve the problem.

[gwpercle]

" Another blow up ".... Time to change something .
Glad you OK but somethings not right .
Gary

[BigAlofPa.]

I find blown out 9mm casings at one of the shooting spots. Wish i could find out who is shooting them. Not sure if he is aware.

[edp2k]

Original AK had that problem, they put a spring on the FP (US imports) to solve the problem.

That is a slam fire, where the bolt locks up and the FP has enough inertia to move forward and fire the primer.
In the cases where this happens typically commercial primers are being used, which are harder than mil primers.
A FP spring can mitigate this problem.
Militaries typically don't want to employ a FP spring as the fore/aft movement of a spring-less FP (imparted by the soldier walking with the gun)
"self cleans" the FP channel and helps prevent FPs rusting/crudding-up in place.

That is very different that the scenario shown in the OPs pics, which definitely fired out-of-battery, thus is not a slam fire.

[Lloyd Smale]

ive got two 9mm ars and ill tell you what I think happened because it happened to me a number of times before I got my 4.5 inch gun worked out. There blow back guns. As soon as the primer ignites the charge the bolt starts back. If you don't have a heavy enough buffer or buffer spring the case can come back to far before the pressure has dropped and it will blow out the base of the case. Cure. run a 308 carbine buffer spring. At least a 5.5 oz buffer and NEVER put a reduced power hammer spring in one because the hammer spring is the first resistance the bolt has in its rearward trip. all three of these cures keep the bolt from coming back prematurely and the heavier buffer spring also helps the bolt come back into battery with more power. I also use a buffer spring cushion that goes on the back side of the buffer spring. It has a couple purposes. One is it keeps the bolt from coming back to far and breaking the bolt hold open if you have a colt mag gun that has a bolt hold open. It also shortens the stroke of your gun and helps the spring push the bolt back with even more speed. Id like to pretend to be the pro that discovered all of this but im not. I talked to a guy that does custom 9mm ars because I was having feeding problems and blown case problems like you. Since then ive put probably 2k threw the gun with a not a single case failure. Another good thing is a feed ramp. The barrel I got with my upper had about no forcing cone and most 9mm ars have no ramp (my cmmg does) . I was told to buy a faxom barrel because they had a more gradual forcing cone. 100 bucks later it didn't look a bit different. then I found where some are putting in a ramp. Its just a small piece that you inlet into your upper. think it cost like 20 bucks and is a 10 minute job and it made my gun feed like butter and chamber about any bullet I use. im sure it also lets your bolt go into battery much easier because the nose of the bullet isn't smacking into the forcing cone.

[Lloyd Smale]

9mm firing pins do have a spring.

That is a slam fire, where the bolt locks up and the FP has enough inertia to move forward and fire the primer.
In the cases where this happens typically commercial primers are being used, which are harder than mil primers.
A FP spring can mitigate this problem.
Militaries typically don't want to employ a FP spring as the fore/aft movement of a spring-less FP (imparted by the soldier walking with the gun)
"self cleans" the FP channel and helps prevent FPs rusting/crudding-up in place.

That is very different that the scenario shown in the OPs pics, which definitely fired out-of-battery, thus is not a slam fire.

[Elkins45]

My 9mm AR from PSA was a grenade waiting to happen. There wasn’t enough resistance to the bolt moving back under pressure. I had to add a heavier buffer and heavier spring to make it safe to shoot.

I think the 9mm AR is problematic in general. I’m probably going to get rid of mine.

[edp2k]

9mm firing pins do have a spring.

Of course colt-system 9mm ARs have a FP spring

if you read my post you will see it is in response to a comment regarding a so-called "original" AK which does not have a FP spring.
Also, to correct the term "original AK", which is a bit misleading, only a few AKs imported into the US for commercial sale had FP springs,
and those were later in the import game.

I recall that it was only very late polytech AKs that had the FP spring, after some experienced slam fires when using US made commercial ammo
which had relatively soft primers as compared to the foreign mil primers, and the large importer KFS (kengs) requested it, as he had some significant contacts in china.
All the AKs in use by foreign militaries and the vast majority of US imported AKs did not have a FP spring.

[nekshot]

I am all about having fun but these type of issues kinda common the way I am understanding this!!?? I feel real warm and fuzzy saying I don't have a blowback ar!

[M-Tecs]

ive got two 9mm ars and ill tell you what I think happened because it happened to me a number of times before I got my 4.5 inch gun worked out. There blow back guns. As soon as the primer ignites the charge the bolt starts back. If you don't have a heavy enough buffer or buffer spring the case can come back to far before the pressure has dropped and it will blow out the base of the case. Cure. run a 308 carbine buffer spring. At least a 5.5 oz buffer and NEVER put a reduced power hammer spring in one because the hammer spring is the first resistance the bolt has in its rearward trip. all three of these cures keep the bolt from coming back prematurely and the heavier buffer spring also helps the bolt come back into battery with more power. I also use a buffer spring cushion that goes on the back side of the buffer spring. It has a couple purposes. One is it keeps the bolt from coming back to far and breaking the bolt hold open if you have a colt mag gun that has a bolt hold open. It also shortens the stroke of your gun and helps the spring push the bolt back with even more speed. Id like to pretend to be the pro that discovered all of this but im not. I talked to a guy that does custom 9mm ars because I was having feeding problems and blown case problems like you. Since then ive put probably 2k threw the gun with a not a single case failure. Another good thing is a feed ramp. The barrel I got with my upper had about no forcing cone and most 9mm ars have no ramp (my cmmg does) . I was told to buy a faxom barrel because they had a more gradual forcing cone. 100 bucks later it didn't look a bit different. then I found where some are putting in a ramp. Its just a small piece that you inlet into your upper. think it cost like 20 bucks and is a 10 minute job and it made my gun feed like butter and chamber about any bullet I use. im sure it also lets your bolt go into battery much easier because the nose of the bullet isn't smacking into the forcing cone.

This would be my bet.

[tomme boy]

It was not the AK's that had a problem. It was the ndm-86 svd, and the SKS rifles. The SKS was because no one was cleaning the bolts and left the cosmo in them. Then they slam fired. And others did some bubba smithing on them to lighten the trigger. The spring that is used for the mag catch was the culprit. It lightened the trigger but also would make it go FA.

The SVD's from China were recalled to put a firing pin spring in them. Reason was they made this one in 308 win. And people running the commercial ammo were having it double triple and slam fire when closing the bolt. CDNN I think still has a recall on their web site for this rifle as this was where you got them from. So there are guns out there that never had it done. Reason for the ongoing recall

I don't ever recall the AK's being recalled for this or it ever added as a safety feature.

[FLINTNFIRE]

Its a blowback this is the issue , why is no working on a gas operated , I have owned a dozen sks and never has there been a issue of slam fire with any of them.

primers and firing pin springs are all good , but no firearm should be capable of firing till it is locked up , Yes I know there are a gross of builders parts and every one putting this and that together , and there is the issue , a little careless a little off put it in anyway , make it fit , lets fire it it is acceptable , on your own range by yourself maybe . oh it is someone elses spleen and insurance and all and there is a problem you have a accident and the other party ends up with a health issue . B.S.

[tomme boy]

The cmmg 9mm AR uses a modified bolt. It still has the regular(modified) bolt. It helps to lock it up so you don't get a OOB discharge. And it also keeps the firing pin shrouded till the bolt rotates and is closed before the hammer can hit the firing pin. Too bad it is patented because then everyone could use it.

[6bg6ga]

ive got two 9mm ars and ill tell you what I think happened because it happened to me a number of times before I got my 4.5 inch gun worked out. There blow back guns. As soon as the primer ignites the charge the bolt starts back. If you don't have a heavy enough buffer or buffer spring the case can come back to far before the pressure has dropped and it will blow out the base of the case. Cure. run a 308 carbine buffer spring. At least a 5.5 oz buffer and NEVER put a reduced power hammer spring in one because the hammer spring is the first resistance the bolt has in its rearward trip. all three of these cures keep the bolt from coming back prematurely and the heavier buffer spring also helps the bolt come back into battery with more power. I also use a buffer spring cushion that goes on the back side of the buffer spring. It has a couple purposes. One is it keeps the bolt from coming back to far and breaking the bolt hold open if you have a colt mag gun that has a bolt hold open. It also shortens the stroke of your gun and helps the spring push the bolt back with even more speed. Id like to pretend to be the pro that discovered all of this but im not. I talked to a guy that does custom 9mm ars because I was having feeding problems and blown case problems like you. Since then ive put probably 2k threw the gun with a not a single case failure. Another good thing is a feed ramp. The barrel I got with my upper had about no forcing cone and most 9mm ars have no ramp (my cmmg does) . I was told to buy a faxom barrel because they had a more gradual forcing cone. 100 bucks later it didn't look a bit different. then I found where some are putting in a ramp. Its just a small piece that you inlet into your upper. think it cost like 20 bucks and is a 10 minute job and it made my gun feed like butter and chamber about any bullet I use. im sure it also lets your bolt go into battery much easier because the nose of the bullet isn't smacking into the forcing cone.

sounds logical

[6bg6ga]

Brass looks surprisingly grungy to be factory

Grungy? Probably the result of going off without being 100% chambered.

[Lloyd Smale]

Yes and no. Yup the psa guns are basically starters. Minimum like I said is a 308 carbine spring, a heavy buffer and a extra power (or at least not a reduced power) hammer spring to hold the gun in battery a bit longer. Now my cmmg 16 inch 9mm has never one NOT ONCE missed a beat. Its probably the most reliable and forgiving ar I own and I own quite a few. Ive put every handload ive ever made for 9s in it. even that pointy 105 lee and it eats them all like candy. But then it was a 1000 dollar gun not a 500 dollar gun. Since I did those upgrades and put in that feed ramp on my psa gun its ran flawlessly too. I guess though id think it wouldn't cost them but a couple bucks more to do it right I the first place. Got mine running great now and id never part with it, even runs perfectly with cheap mags. It fits perfectly in a 10-22 take down case and its sits strapped to my roll bar over the rear tire well in the jeep. I painted over the ruger emblems and nobody would ever guess that little pack had a gun in it. ****?? it there with 5 30 round mags. I did here that the new version of psas 9mms have addressed some of these problems and do run better. But that said if you buy one youd better figure in about 75 bucks to get it running right. Before you give up look on psa web site. they sell that little feed ramp you fit into them. Heavy buffer (at least 5.5 oz) and even a standard length carbine spring will probably get you running perfectly.

My 9mm AR from PSA was a grenade waiting to happen. There wasn’t enough resistance to the bolt moving back under pressure. I had to add a heavier buffer and heavier spring to make it safe to shoot.

I think the 9mm AR is problematic in general. I’m probably going to get rid of mine.

[Lloyd Smale]

mine also has an actual feed ramp. that's the biggest thing that makes me shake my head with most blow back ars. No feed ramp what so ever. Just a bit of taper at the end of the barrel. I have to agree with you in that the cmmg bolt and barrel are the hands down best blow back ar system made. They just don't give them away though.

[243winxb]

Bullet set back from hitting a feed ramp on chambering may produce a kaboom, even in a low pressure 45 acp. This Hi-point 40 S&W Factory ammo at 35,000 PSI did kaboom.

The OPs photo shows a round not fully chambered when it fired. Was it going in or comming out of the chamber?

Blow back actions should not be made for 35,000 PSI cartridges. Imo.

[popper]

Wasn't slam fires that required the use of FP spring, they would go full auto.

[tomme boy]

PSA guns have a feed ramp on the bottom of the barrel now. At least mine does. Along with the cone all around the chamber. The feed ramp is not much but it is there.

I have mine sent back to PSA right now. The bolt is *****ed. I started to see wear on the outside of the bolt. It is nitrated so there should be NO wear. It is supposed to be the new wonder treatment for steel. Well it was wearing off all around the bolt. Then I checked the bottom of the bolt and it was ****ed up. There was a gouge in the receiver also.

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