New to AR-15, When I chamber a round then eject it the primer is dented

[DoubleTapDrew]

I've seen picture-tube monitors/TVs successfully stop rounds up to 7.62x39 steel core from very short range.
Today 09:09 AM

I've um...heard...yeah...that a 13" TV/VCR combo, followed by a double pane window will stop a 7mm-08 at very short range
Never had a slam fire with an AR, although I haven't started handloading .223 yet. I'll have to watch primer depth.

 

[Slamfire]

By Gum AR's do SlamFire!

Yes they do. I am a competitive highpower shooter and had an AR slamfire during the standing stage. I dropped the round in the chamber, dropped the bolt, and blam! scared everyone and took a big divot out of the ground about ten feet in front. The next relay HM on my point laughed at me, then had a slamfire with his AR during his offhand stage!


I used the new more sensitive WSR, and he was using Fed Match.


Ever since I had an out of battery slamfire with a Garand, I seat all rifle primers by hand with the Lee hand primer. I did not have a high primer.

Slamfires happen in AR's, and they typically happen when a round is put in the chamber and the bolt is released. Thank goodness I have never heard of an out of battery slamfire with an AR. Now days, when single loading standing, I drop the round, hold the cocking rod, hit the bolt release, and lower the bolt half way before letting go. Then I bump the forward assist.

The military had a lot of slamfires in M16's, and then they redesigned the firing pin to make it lighter. Still with these sensitive commerical primers, you still run the chance of a slamfire. I used CCI41 in my rifles. I still have a couple thousand of the old nickle plated WSR, they were great primers and less sensitive than the brass finish ones.

 

[RecoilRob]

The issue of slam-firing when single loading has been talked about before...but to anyone here that hasn't heard, the practice is outside of the normal designed operation.

The AR's are intended to feed from the magazine and this resistance slows the bolt down to a (normally) safe speed.

Dropping the bolt on an already chambered round, without magazine, is kind of pushing the design and although many thousands of people do this ever year, it is not a defect of the rifle when one goes BANG.

Load every round from the mag and it is highly unlikely you will ever get more than a tiny, light dimple.

 

[Wild Deuce]

Hmm ...

Occured today while breaking in a new upper ... single round in the mag, pressed the release and ... BANG! A little later on, with three rounds in the mag, pressed the trigger ... round fired. Everything is ok. Pressed the trigger again ... double BANG!

I went back to single loading to finish out the box. Total rounds fired ... 40. Two slam-fires (including the double). Two failures to extract. One failure to feed.

Gotta sit and figure this one out. It's a brand new upper and the gun was squeaky clean and properly lubed. First slam-fire was on the second round fired (while I was still single loading the magazines). The double was on rounds 27, 28 (of 40).

At this point the ammunition is my prime suspect, Winchester "White Box" .223 Rem, 62 grain but I would have to say that ARs do, in fact, slam-fire.

 

[Bartholomew Roberts]

Is there debris in the firing pin channel where the firing pin is stuck forward?

 

[SSN Vet]

Any suggestions for preferred "slightly harder" primers for autoloaders?

I'm using Winchester Small Rifle Primers with no trouble for my AR...

I think either WSRP or CCI are fine....

just avoid Federal primers for auto-loaders as they are reputed to be the softest of the bunch.

 

[Wild Deuce]

No debris, BR.

I neglected to mention that I did inspect for a frozen pin after the first slam fire. I didn't expect one (frozen pin) since I had personally cleaned and inspected the gun last night and it was the second round of the day. I also didn't expect it to foul up too much since it is a piston operated upper (ZM Weapons).

The more I read the more I realize that I should have been using 5.56 surplus instead of commercial .223 Rem ... especially Winchester "White Box" ammunition. Anyone want to buy several boxes of WWB .223 ... cheap?

 

[AR-15 Rep]

The optimum thing to remember, no one knows for sure if the round you are chambering will slam fire or not, chances are it will not but keep safety in mind.

 

[Wild Deuce]

I'll say it was surprise. I did have it pointed downrange and saw it impact the berm. Still, that was my first slam fire ever and my first unintended discharge ever.

 

[Stevie-Ray]

And if neither of those are handy, I've seen picture-tube monitors/TVs successfully stop rounds up to 7.62x39 steel core from very short range.

Hmmm.....hangin out with Elvis?

I've also heard that CCI primers were the hardest.

 

[Bartholomew Roberts]

Thank goodness I have never heard of an out of battery slamfire with an AR.

That is because the AR bolt design is such that the firing pin cannot protrude through the bolt face unless the bolt is locked. So the only way you can have an out-of-battery slamfire in an AR is if something else (bolt face) detonates the primer.

The more I read the more I realize that I should have been using 5.56 surplus instead of commercial .223 Rem ... especially Winchester "White Box" ammunition.

A whole lot of commerical .223 goes through ARs with no issue, especially WWB. I think you may have an iffy lot of ammo though.

 

[Wild Deuce]

A whole lot of commerical .223 goes through ARs with no issue, especially WWB. I think you may have an iffy lot of ammo though.

You're right but the fact remains that I've lost confidence.

I'm now eyeballing Prvi Partizan in either the M193 (55 Grain) or the M855 (62 grain). Federal XM193 (55 grain) is also an option.

I just have to figure out the primer issues and corrosiveness issues.

Thanks for your thoughts.

 

[strat81]

Current production Prvi 5.56/.223 is non-corrosive and the brass is reloadable. Same goes for XM193.

As for your WWB, you cannot ship ammo via USPS. Fedex and UPS will ship it but you'll need proper ORM-D labeling.

Are the primers on that ammo seated properly or are they sticking out? For the doubling, are you sure your lower's FCG is functioning properly? Worn parts can cause doubling.

 

[Wild Deuce]

The upper was brand new and unfired (except for factory). The lower is a relatively new (about 200 rounds) RRA. Both (upper and lower) were cleaned, inspected and lubricated properly before the trip to the range. The lower has functioned flawlessly for those 200 rounds when mated to a White Oak Armament upper (all Black Hills .223 Rem 77 grain).

The WWB ammunition isn't the prettiest thing (unlike the shiny new brass of my Black Hills) but it all "looks" ok. None of the primers look high from any of my remaining boxes and I did inspect the ammunition after my first slam fire ... nothing noted. However, I did note the primers looked different after the slam fires than the rest of the fired ammunition. It seems that would be odd if the rifle was in battery. I know BR said that the bolt face could cause the slam fire but the two casings did have firing pin strikes with no other dimples or scratches on the primer face.

I am begining to suspect the recoil spring on the ZM upper. It does seem rather robust. This upper might require the harder primers found in 5.56 NATO. Unfortunately I don't know it all yet so I'm still researching.

I do have another range trip planned for this Sunday so if anyone has any suggestions on how to help identify the problem without destroying the gun, I'm all ears. I already have in my possession 5.56 ammo from Prvi Partizan M193, M855 and Federal XM193 as well as assorted .223 from Winchester (the stuff that slam fired), Black Hills, Hornady TAP and Federal (Tactical).

STRAT81: You say the Prvi stuff is reloadable. Can I assume that it's boxer primed then? I guess I'll find out Sunday anyway, Thanks.

 

[AR-15 Rep]

Deuce, can you put some pics up?
would like to see the hammer face,
the BC rear, side view of hammer, and whatever view you might deem usefull.

 

[Wild Deuce]

These are the casings. The two across the top are the slamfire casings. The two across the middle fired normally. The two across the bottom are unfired rounds from the same lot.

Second picture has the two slamfires on the left and two casings that fired normally on the right.

 

[Wild Deuce]

The hammer ...

 

[Wild Deuce]

Bolt carrier, rear of the bolt carrier and view of the bolt face ...

 

[Wild Deuce]

a little closer view of the bolt ...

 

[Bartholomew Roberts]

Hmm, looking at the slamfires vs. the normal fires, it looks like they are just getting the normal light tap from the firing pin. That looks like the dimple in the middle. After that something else is setting off the rounds and the primer is expanding into the firing pin hole.

I'd look at the ammo or the spring.

 

[Wild Deuce]

I ran 60 rounds of the WWB through my Wilson Combat without a problem today.

I also ran fifty rounds each of Prvi 5.56 M193 (55 grain), Prvi .223 (62 grain) and Federal 5.56 XM193 (55 grain) through the ZM upper without a single malfunction.

My opinion, the WWB is too sensitive for the ZM recoil spring and I am better off with the 5.56 ammunition. Even the Prvi .223 Rem ammo ran fine in the ZM upper.

As a side bar, the Prvi ammo runs pretty hot (no chrono but recoil and report was much sharper) ... even the .223 stuff. Groups were superb though.

 

[Slamfire]

Mr Wild Deuce: I hope you don't mind if I copy your pictures for future slamfire discussions.

Back in 1999 Winchester changed their primer line. One difference was that the good old WSR primers were nickel plated. Now they are brass colored. I called them at the time and asked them if they had done something else, and yes, they made their primers more sensitive.

I had one AR slamfire with a brass colored WSR. It was in standing slow fire, I placed a round in the chamber and dropped the bolt. The round went off. The primer indentation looked normal. Actually, I was unable to identify the slamfire round, when I picked up my 22 cases of brass from behind the firing line, they all looked the same.

What is unusual about your slamfires is the depth to which the primers have flowed back into the firing pin hole. However folks should not read too much into this, after all the firing pin was not being held forward by the hammer, so maybe what you have is “normal” for AR slamfires.

Now there is this default fault attribution in the shooting community. If you have a slamfire a whole bunch of people will claim it is due to high primers. No reason, its just the cultural norm. However, after spending time looking at this issue, I believe the vast majority of slamfires are due to overly sensitive primers. You are shooting factory ammunition. And you are shooting it in a weapon with a free floating firing pin.

My conclusion, Winchester ammo, primed with Winchester primers is too sensitive to shoot in your rifle.

Shoot something else.

 

[Blackfork]

Slamfire or hammer follow?

You can get either with some of the target triggers that get installed. Usually the sear adjustment has gotten too light on hammer-follow.

I intentionally make a few high primer rounds for teaching juniors to be alert when they are firing ARs in offhand, single load. it's easy to make one go ka-boom when they drop the bolt. Drives the point in about muzzle control. I would only do it in a one-on -one session so I am right there waiting for it to happen.

Teaching Army shooting I always noted this with the soldiers. I wouldn't put the same round back in the chamber and drop the bolt on it over and over. Too many kisses and the bullet may think its a date.

For the record I'm careful dropping a slide, a bolt, closing a bolt action, et, et. Keep that muzzle downrange and controlled.

Safety first, last and always.

 

[Blackfork]

Worn Bolts

I've worn out a couple of bolts in ARs- and the wear was on the inside of the hole where the firing pin protrudes. You get a couple of pierced primers while testing loads and it erodes the tip of the firing pin, making it MORE likely that it will pierce primers, then the inside of the hole in the bolt erodes from the hot gas coming back through the primer so that the firing pin comes through the hole a little more, then everything goes to heck in a handbasket rather quickly.

These are ARs shooting very hot match loads with heavy bullets. When I see an eroded tip on a firing pin I pass out a new one, and keep a few extras around.

I can't tell from the photo whether yours is eroded or not but I see some suspicious double dents in those primers.

We are handloading with CCI 450 primers for .223 for National Match team shooting. I'm still using win small rifle from River Valley Ordnance for 200 and 300 line ammo.

You can see eroded tips from the actual tip of the firing pin or the primer indentation on the shell casing. Very hard to see the erosion inside a bolt, though there is a tool to measure firing pin protrusion.

Parts pretty cheap.

Nice photos.

 

[Wild Deuce]

Slamfire1 ... enjoy and use the pictures in good health. Anything to educate. BTW, thank you for giving me a clue about the probable cause for the flow back into the firing pin hole that is evident on the slamfired primers (no hammer holding the pin forward).

To summarize:

• The ZM upper has a robust spring
• The ZM prefers 5.56 NATO spec ammo with the harder primers
• WWB .223 Rem ammunition has sensitive primers
• The Wilson Combat M4TAQ will digest WWB .223 without a problem
• Be aware of the muzzle when chambering a round in ANY firearm

Thanks to all for the advice and information.