My love hate with a Ar9

Tomme boy

Well-Known Member
Old ladies brother and kids are in town for a few weeks. So today was perfect to go to the range. Brought 4 Ar15's and my G19 and my Ruger bolt in 350 legend. Everything was shooting awesome.

Then this.
20210801_002726.jpg

I love shooting this thing in 9mm. It is crazy accurate. Even out to 300 yards. But, it will fire out of battery. This is the first time the bullet made it into the bore. It went about half way through before stopping. That is the bullet. 135gr 2r from mp. This has happened a few times. I have not been able to see what is actually happening. I was slow firing. So I was not bump firing as that makes it happen all the time. The only thing I think what it may be is resting the gun on the mag. The bolt drags on the mag if you do this.

But the case was not fully into battery. That extractor is one tough sob. Anyway, I have about 700 rounds with this bullet loaded left. I have another 135gr that does not have to be seated as deep as this one. I have not had any problems with that one it has a longer oal and feeds better.
 

Ian

Notorious member
An AR should NEVER fire out of battery. Even the blowback style bolt should have the correct shape around the firing pin head to catch the hammer if the bolt isn't fully forward. What you have there is DANGEROUS.
 

Tomme boy

Well-Known Member
All but the cmmg delayed action ar9 rifles can and will do this. So can most other blow back rifles.

The bullets are sized to 0.3555" after coating. I am sizing all of my bullets to fit my G19. It has a very tight chamber. If you go over 0.356"+ anything they are tight to remove. But none of the 9mm I have now lead at all sizing this small.
 

Ian

Notorious member
The only time an OOB firing should ever be a worry is with a system that operates from an open bolt and has a fixed firing pin. I can't think of any good reason why Stoner's excellent design would need to be compromised when eliminating the the rotating bolt head. Unless the sear is bad and letting the hammer follow the bolt, the hammer should not be in position to send the firing pin all the way forward unless the bolt is fully in battery. My AR-45 is a DI gas gun and I've had more than one failure to fully chamber...but it always results in a "click" and slight mark on the primer cup and not a kaboom in my face.

Can you describe what is different with these blowback conversions that allows the OOB discharge to occur?
 

Rick H

Well-Known Member
Something is seriously wrong there. I would not fire that thing until I figured out just what. If it is inherent in the design, then get rid of the POS and get something that works properly. There is no way a round should be going off without being fully chambered.
 
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Tomme boy

Well-Known Member
Like I said. I think the bolt dragging on the mag may be the issue. I have a 8 oz. Buffer I am going to put back in. It has the factory 5 oz in it right now. Some have said that having a too light of buffer and this can happen. It allows the bolt to move back under the initial firing and the case then blows out.
 

Petrol & Powder

Well-Known Member
A gun that has a fixed firing pin, such as many submachine guns that fire from an open bolt, could potentially fire out of battery if the cartridge stopped before it was fully in the chamber.

However, a gun that has a hammer and a floating firing pin should not be capable of firing if the bolt is not fully closed. The safety system that prevents the hammer from being released when the bolt is out of battery is not dependent on bolt speed. Nor does it matter if the system is a simple blowback or some type of locking bolt. There should be some type of “out of battery” safety that prevents the hammer from dropping if the bolt is not fully closed.

I think you have more than one problem.
 

CWLONGSHOT

Residing in New England
Tommy,

Try feeding a 10mm Blowback!!

Blow backs have a bad habit if tearing cases in half too!! Its all about the pressure curve of the powder you choose! Choose it wrong and blown cases and torn off heads or rims will be common. This is where a heavier buffer helps.
As stated the design of a AR inhibits chances of firing out of batters simply cause when bolt is rearward ever so slight... Hammer cannot reach FP head.
BUT STAKE YOUR LIFE on its ability to strip a case outta a chamber and if the pressures are still high but the case walls didnt cement that case i to the chamber... She WILL BLOW as the case gets weak ahead if the web.

Glad you OK. You don't Necessarily need to load lightly but you do need to carefully choose powders.
CW
 

popper

Well-Known Member
hammer and a floating firing pin should not be capable of firing if the bolt is not fully closed.
Wrong. I had a AD from ar10 308w when dropping the bolt on a live round. Tolerance stackup in the system and too long a shoulder.
 

fiver

Well-Known Member
I look at it like this.
there wasn't enough pressure to push the bullet out of the barrel.
sooo it went somewhere else.
 

Tomme boy

Well-Known Member
It does not have a floating firing pin it has a spring to keep it back. And it will fire out of battery. I can insert a primed case into the chamber and pull the bolt back to half the case Is backed out of the chamber and it will lite the primer. The firing pin sticks out of the back of the bolt about 1/8".

It does not work like a regular ar15 bolt design in 556 where the firing pin is shrouded.

Went out tonight and ran 100 rounds through it with the heavier buffer. It ran fine. I tried putting pressure on the mag to see if that might be what was making it do it but it ran fine. It happens so randomly it might not do it again for another 1K rounds or so.
 

CWLONGSHOT

Residing in New England
I think CW hit the nail on the head.

It is far more likely that the OP's gun fired from a closed bolt but the bolt opened too soon. The pressure hadn't dropped and the casing blew out as it was being withdrawn from the chamber before the pressure dropped.
The bolt opened too soon.
I have three of them. (Blow back PCC) the 10mm is the worst IF IM NOT CAREFUL choosing powder. My 40's have been fine. Im building a 357 Sig and this one kinda worries me... My one 40, has ripped a half doz cases in half!! I see MANY guys in competition with exact issue Tommy describes. I didnt think about it hut he is right these here do not have a spring on the FP either.

CW
 

RBHarter

West Central AR
Sounds like a SRP or Mag SPP might be a good idea here , kind of like the #41 for 223 etc . Just a little more cup integrity/density/strength to avoid the slam fire/OOB jam fire maybe .

I had 1 slam fire once in an SK . Didn't like it . If it will or does slam or oob it can runaway and empty a mag . Not a big deal on the bottom half of a 10 round on target but it could get pretty interesting on a 30 round stick or a larger snail mag on a charging drop .
 

Petrol & Powder

Well-Known Member
Sounds like a SRP or Mag SPP might be a good idea here , kind of like the #41 for 223 etc . Just a little more cup integrity/density/strength to avoid the slam fire/OOB jam fire maybe .

I had 1 slam fire once in an SK . Didn't like it . If it will or does slam or oob it can runaway and empty a mag . Not a big deal on the bottom half of a 10 round on target but it could get pretty interesting on a 30 round stick or a larger snail mag on a charging drop .
I don't think it is firing out of battery.
The bolt is closing and the round is firing after the trigger is pulled. HOWEVER, after the cartridge fires, but before the bullet exits the barrel, the bolt is opening and the casing is failing as it comes out of the chamber. The bolt is opening too soon.

A harder primer will not affect this issue because the problem isn't early ignition or some type of out of battery firing.
A stronger buffer spring, a heavier bolt, or both, is the solution. It is unlikely he is suffering a slam fire but it is highly likely that the bolt is opening too soon AFTER the round is fired.
 

Ian

Notorious member
The bolt is closing and the round is firing after the trigger is pulled. HOWEVER, after the cartridge fires, but before the bullet exits the barrel, the bolt is opening and the casing is failing as it comes out of the chamber. The bolt is opening too soon.

This. Like Tomme and CW have both said, mismatch of ammunition to bolt mass.