9mm blow up

[joatmon]

Dang!! And here I set just about ready to finish up my 9mm AR and now I see ABOUT ALL OF THIS! But now I can order the 308 buffer spring and heavy buffer.
Mighty glad I opened this topic. Aaron

[6bg6ga]

Recently shot my brothers 9mm AR build. It works flawlessly shoots anything and asks for more.

[Lloyd Smale]

holy ****! that sure got chewed up. I wouldn't be happy myself. I had a bit of wear on mine because the bolt was scraping on the ejector but a bit of filing on the ejector and readjusting it solve that. You don't happen to have a picture of that feed ramp on your barrel by chance?

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.

https://www.ar15.com/media/mediaFile...847-944688.png

[Lloyd Smale]

They been making blowback 9mms since before ww2. You can even get a blow back 10mm today. Blow back guns are no more unreliable then gas guns or locked breach guns. As a matter of fact some of the military guns that are considered to be the most reliable are guns like the Thompson that even fire open bolt. Ask some ww2 guys which gun was more reliable the Thompson or the m1 carbine that was gas operated. Mp5s are another. Even take a look around the internet doing a search for high point rifles and the #1 word you will hear is RELIABLE! Now some poor handloads that don't have enough neck tension or crimp sure can cause troubles in any gun. Take a 454 freedom arms pistol. A gun that's built like a swiss watch and load some full power stuff and us brass that doesn't have good neck tension or isn't crimped well and start shooting a cylinder. After each shot measure the overall length of the rounds remaining and you will find that without a good crimp you will get set back. Plenty enough to make pressures sky rocket.

So are we saying that a revolver should never be loaded past 38 spec pressures? Ive even seen rounds in a magnum bolt action gun get set back because of recoil. If blow back was actually dangerous do you think in this age of rem getting sued because people cant keep there finger off the trigger until they want there gun to go off that blow back guns would even be made? Nope. even gas guns can blow up if there not set up right or use sub standard ammo.

Actually if you look at a blow back Ar bolt youd see there much less that can fail. It doesn't have to rotate so its a one piece design. Doesn't need gas rings doesn't have a button and spring ejector, doesn't have a gas tube that can foul or need to be tuned for gas pressure. Doesn't need a gas block or gas block staking, Tuning is done with bolt weight, buffer and buffer spring. they don't have hot and DIRTY gasses channeled into the bolt. Things that some have switched to gas piston guns to get reliability. Same things you still have to do to tune a gas ar and they have to even be tuned for gas pressure. Once you learn the idiosyncrasy's of a 9mm ar there no harder to get to run right then any other ar. Ill say this. Ive got a 4.5 inch 9mm ar that I think runs just fine. You go and build yourself a 5 inch 556 or even a 7.5 in. My gun will run bullets from 120 to 147 loaded light or full power without change a thing. You take that little 7.5 or shorter 556 and run some 55s light and heavy and some 69s light and heavy and see if your gun runs them all without changing buffers springs gas pressure ect. Ive got a 100 bucks up against your 10 that my 9mm blow back ar has less hiccups then that little flame thrower you have. Did it come that way out of the box? NOPE it took some tuning and was a learning experience because tuning is different then a gas gun. That said my 16 in 300 bo need a heavier buffer to run right and took some grinding on the feed ramp to run cast bullets a 100 percent and even they is fussy which cast bullet it will feed (the 9mm feeds any cast bullet) My 8.5 inch 556 pistol took a heavier buffer and spring then the short pistol spring and 3.5 ounce buffer that came in the kit. It now runs a standard carbine spring and a 4.6 once buffer. Heck I still remember back in the day that guys would say just going to a carbine length gas system vs a rifle length original system made an ar unreliable.

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.

[tomme boy]

Llyod, no I don't have a pic. PSA has it right now. Waiting to hear what they say. There was also a huge gouge in the rear of the receiver.

[243winxb]

Heavy springs and bolt that retard blow back , cause problems when they move forward. This is
more likely to cause slam fire or out of battery firings.

The 45 acp runs at 21,000 PSI, , less the the 22 lr at 24,000 PSI. COMPARING 9MM (35,000 PSI) + 10MM (37,500 PSI) hardly comes close..

Post #25 is a good example why i dont want a blow back carbine.

[Lloyd Smale]

Like I said if the dangers were real in this liability era were in they wouldn't be selling them. There have been open bolt and blow back 9mms since the 9mm was introduced. Problems come with guys that think they know more then the do. Just like the hack gunsmiths that adjust rem triggers. Now take a blow back 9mm ar and start doing back yard gunsmithing like putting a reduced tension hammer spring. Lighter buffer spring or buffer, Take the weight out of the bolt. Make sure you gun is nice and dirty so the firing pin sticks, feed it crappy handloads that don't pass a chamber drop test ect ect and you can make the do bad things. Set them up right and feed them right and keep them clean and they are as reliable and safe as any gun. Yup heavier springs cause problems when the bolt comes forward. Its why 9mm ars have a heavier buffer too. Twice as heavy as a 556. To slow the bolt down. Use a carbine buffer because you don't understand this and you will have trouble. I don't know if they address it with the new one or not but the problem that psa had wasn't using to heavy of a spring. It was using a heavy buffer with to light of a spring. they used a standard thickness carbine spring made lamer by cutting it to pistol length. This made it loose to much power and speed for the bolt going back into battery. Like I said the guys that know use full lenght ar10 carbine springs. Not only keeps more pressure on the bolt to delay it starting back but also gives that heavier bolt a better push back into battery. We can argue till the cows come home. Bottom line is im arguing with guys that haven't even tried it. Guys that are listening to what someone else heard for someone else who heard it from someone else. Like I said bring you gas impingement gun and a wad of money and first burp wins. You might win and you might not but before you even think about trying make sure your gun will run at least 500 rounds without cleaning and reoiling because mine sure will. Lots of guys claim that the gas impingement system is flawed and its why gas piston guns were made. Nothing like filling the inside of your bolt with carbon and gunk. ME? My gas impingement guns work just fine too. I know how to clean them

[Lloyd Smale]

by the way I found a cool use for my little 9. Found it fits perfectly in the little ruger 1022 take down case. Painted the ruger emblem black so it doesn't attract attention and stuck 4 30 round mags in the case with the gun and it sits perfectly on the wheel well between the roll bars feet in my jeep. Id bet about nobody would expect it was a gun let alone something with that kind of firepower in such a small package. Heck and you don't even have to put it together.

[tomme boy]

Lloyd. Supposed to have it back tomorrow. I will get a pic for you.

[Lloyd Smale]

thanks. Id like to hear what they had to say caused that extreme wear on the bolt too.

Lloyd. Supposed to have it back tomorrow. I will get a pic for you.

[dverna]

One reason I normally like to have another person with me when I am shooting is for safety. Stuff happens with any gun...even a bolt gun can have a case separation.

It is easy to think all is good. Especially when I have fired over 500k rounds without incident....but it only takes one bad event.

Reading posts like this are a good reminder for all of us.

[tomme boy]

Well the bolt showed up today. I just got another notification that the upper is shipped separate and will be here tomorrow.

Nothing in the box that said what happened.

[tomme boy]

Here is a pic. They replaced the upper receiver and bolt. Nothing was in either box to say what they actually did or what was the cause.

[jonp]

Pics#1 & #3 seem to indicate it wasn't fully chambered when the primer went off, which may mean that it fired while bolt is loading the round.
Good thing no one got hurt.

My guess, too but I don't have a pistol caliber AR

[Lloyd Smale]

is that cut in the lower part of the forcing cone what your calling a ramp? I did that to my first barrel with a Dremel and it did help a bit but made me nervous removing material that supported the case. That's when I bought the faxon barrel which was suppose to have a better forcing cone but I sure could tell the difference. It is a little more accurate but that might be just luck of the draw. there is a company that sells a barrel that has an actual ramp and a bolt cut to fit it https://taccom3g.com/product/5-25-9mm-ramped-barrel/. I just couldn't see buying a third barrel and another bolt when the 20 dollar add a ramp worked great. But if I was going to do a 9 today id buy a psa glock lower and a bare upper and go with the ramped barrel and bolt.

Here is a pic. They replaced the upper receiver and bolt. Nothing was in either box to say what they actually did or what was the cause.

[tomme boy]

Mine has fed everything so far.

[redneck1]

A popular misconception on blowback guns is that a heavier buffer spring will fix firing out of battery problems .

A simple fact is a heavier spring won't make any differance at all , if you'd like we can trot out the math , blowback guns rely on mass alone to delay bolt movement long enough for pressures to drop and not blow out the case .

The only purpose of a buffer / recoil spring is to return the bolt to battery to fire the next round .

I fully expect a few here to argue with me on that , before you do spend some time researching it .
I am no expert , but bolt mass is the entire reality with blowbacks.
Not mass and springs

Now there is one exception where a spring can make a differance , that is if the spring is short to hold the bolt into battery on a closed bolt gun .
A longer spring can fix this . A higher spring rate won't fix a short spring .

[Petander]

B&T APC9 bolt is heavy for a reason:

[Lloyd Smale]

now answer me this. If I put a block of steel on a table and measure how much force it takes to get that block of steel moving and then repeat it with a big heavy spring behind it your saying that that spring has done nothing. Funny thing is that theres a company that specializes in 9mm ar15s. they build them and sell upgraded parts for them and even set them up to work a 100 percent with binary triggers. talk to them about what works and what doesn't. I did and the first thing they told me when I described my gun was to take out the reduced tension hammer spring and put a heavier (308 carbine) recoil spring. Now these guys have been there and done that. they KNOW what works. Even if it didn't (which it does) slow down the bolt from coming back the heavier spring surely adds velocity and power to the bolt return which would sure, by using common sense, tell me that theres a better chance that round is going to be shoved all the way into battery before my finger pulls the trigger.

There advice gets 9mm ars to run a 100 percent at the speeds you can manipulate a binary trigger. If you have some real world experience with 9mm ar15s then id sure would love to learn it. All I can say is mine has ran flawlessly since I took there advice and im sure since them ive put at least 2 or 3k though the gun.

My test for a new 1911 used to be oil the gun shoot a 100 rounds. Pull it apart clean it and run 500 through it without touching it. Clean it and do the same. If it passed that test id trust my life to it. Well this 9mm ar has easily topped that. Pretty good for a gun that is a defective design. Kind of like those unreliable glocks with there unsupported chambers. If you have any you should immediately ship them to me before one blows up and hurts you.

Lots of theory and to many gun design experts here and not much real world going to the range and making a gun go bang a few thousand times. Like I said bring your 556 and a wad of cash and we will do a shoot till somethings fails contest. Let me use my cmmg 16 inch 9mm and PLEASE bring your house title because that gun is the most reliable ar15 ive ever owned and came that way right out of the box. No moving ejector, rotating bolt with lugs that can break, no gas rings, plugged gas tube, gas block slipping out of position, no gas keys bolts to come loose, No bolt full of carbon inside, no lugs in the barrel that can plug up with grime of get a piece of brass stuck in them. No need to oil the locking lugs or bolt internals that's a magnet for fouling. light coat of oil on the outside of the bolt and when it gets filthy pull it out wipe it off put a light coat of oil on it as stuff it back in and keep going. Heck wipe it on your shirt and stick it back in. mine runs fine dry. Good luck when someone shooting back pulling your bolt apart to clean the fouling or digging out your gas key bolt that came loose and probably tore up the inside of your gun. Ill leave this one to the experts now. Other then hanging around to see how tomme's gun pans out. that is unless this thing fires out of battery and pokes my eye out.

A popular misconception on blowback guns is that a heavier buffer spring will fix firing out of battery problems .

A simple fact is a heavier spring won't make any differance at all , if you'd like we can trot out the math , blowback guns rely on mass alone to delay bolt movement long enough for pressures to drop and not blow out the case .

The only purpose of a buffer / recoil spring is to return the bolt to battery to fire the next round .

I fully expect a few here to argue with me on that , before you do spend some time researching it .
I am no expert , but bolt mass is the entire reality with blowbacks.
Not mass and springs

Now there is one exception where a spring can make a differance , that is if the spring is short to hold the bolt into battery on a closed bolt gun .
A longer spring can fix this . A higher spring rate won't fix a short spring .

[redneck1]

Eating lunch and I realized I forgot one thing in my post , if a gun is capable of firing out of battery , anything you do with recoil / buffer springs isn't fixing the problem . It may mask a few conditions
But it won't fix any of them .
If the hammer or striker can fall on the firing pin with the bolt out of battery that's a big problem .