Punctured Primers on New AR 9 Build

teratos · May 9, 2020

MADad said:
Teratos , were you kidding about going full auto if you file the pin down? Maybe a stupid question, but I have to ask.

Yes. If you listen to keyboard commandos, an oft repeated tale is that AR’s are easy to convert to full auto....you just have to file down the firing pin.

calicojack · May 9, 2020

teratos said:
Yes. If you listen to keyboard commandos, an oft repeated tale is that AR’s are easy to convert to full auto....you just have to file down the firing pin.

Damn! I just filed down all my AR firing pins!!!

KIDDING.

calicojack · May 9, 2020

outrider58 said:
Just checked my SBR9 .036

And next, my pistol .036

Moral of the story; never measure firing pin protrusion on your birthday.

*changed post#10*

Outrider; appreciate the assist. :thumbsup:

So even if my el cheapo calipers are off, sounds like I am in the ball park. Your firing pin looks a lot smoother than mine. Foxtrot Mike is sending me a new one, and I ordered a titanium as well as a backup.

wilcam47 · May 9, 2020

Dumb question but did you try different ammo?

outrider58 · May 9, 2020

calicojack said:
Outrider; appreciate the assist.

So even if my el cheapo calipers are off, sounds like I am in the ball park. Your firing pin looks a lot smoother than mine. Foxtrot Mike is sending me a new one, and I ordered a titanium as well as a backup.

My pleasure. Sorry about my original goof.

calicojack · May 9, 2020

wilcam47 said:
Dumb question but did you try different ammo?

Yes - three different kinds. The other two did nut puncture as frequently, but I still got punctures.

3paul10 · May 9, 2020

teratos said:
Yes. If you listen to keyboard commandos, an oft repeated tale is that AR’s are easy to convert to full auto....you just have to file down the firing pin.

Well damn doc....I'm filing down my fingernails too!

calicojack · May 9, 2020

3paul10 said:
Well damn doc....I'm filing down my fingernails too!

I'm not going to ask what that has to do with full auto.

Trigger Time · May 9, 2020

Have you checked the head space ?

calicojack · May 9, 2020

Trigger Tuner said:
Have you checked the head space ?

I have not. The thought has occurred to me. Although, this is what I was thinking:

1. If there is too much head space (i.e. too loose), I would think I would get light primer strikes.

2. If it were too tight, that could certainly cause a deeper primer strike. I would think it would have trouble going into battery. Hmm - is that necessarily true?

Probably would be a good idea to get a 9mm Go gauge and see. I would have to figure out how to remove the extractor from that bolt.

outrider58 · May 9, 2020

calicojack said:
I have not. The thought has occurred to me. Although, this is what I was thinking:

1. If there is too much head space (i.e. too loose), I would think I would get light primer strikes.

2. If it were too tight, that could certainly cause a deeper primer strike. I would think it would have trouble going into battery. Hmm - is that necessarily true?

Probably would be a good idea to get a 9mm Go gauge and see. I would have to figure out how to remove the extractor from that bolt.

Should be a roll pin angling through the top of the bolt towards the front.

danb · May 9, 2020

MADad said:
Teratos , were you kidding about going full auto if you file the pin down? Maybe a stupid question, but I have to ask.

Not the good kind of "full auto" - more the "runaway gun" kind of full auto where you mag dump out of control, possibly even have some out of battery discharges. Its a thing of much internet rumor and speculation.

outrider58 · May 9, 2020

calicojack said:
I'm not going to ask what that has to do with full auto.

I'm not sure, but I feel his comment was below the belt...

calicojack · May 9, 2020

outrider58 said:
Should be a roll pin angling through the top of the bolt towards the front.

Ah yes - I found it.

So let me ask you this; there is no ejector in the bolt. Can I get away with leaving the extractor there if the gauge fits?

[EDIT] Clymer says:
"It is best to remove the extractor, ejector, and firing pin from the bolt to achieve optimal results when checking headspace. "

outrider58 · May 9, 2020

danb said:
Not the good kind of "full auto" - more the "runaway gun" kind of full auto where you mag dump out of control, possibly even have some out of battery discharges.

First AR I ever bought did that. No OOBD though. Just a full uncycled mag dump. Bad sear, I guess? Replaced FCG. Threw the old crap away.

outrider58 · May 9, 2020

calicojack said:
Ah yes - I found it.

So let me ask you this; there is no ejector in the bolt. Can I get away with leaving the extractor there if the gauge fits?

[EDIT] Clymer says:
"It is best to remove the extractor, ejector, and firing pin from the bolt to achieve optimal results when checking headspace. "

I guess it depends on where the ejector is located?

calicojack · May 9, 2020

outrider58 said:
I guess it depends on where the ejector is located?

In the lower behind the mag well.

Trigger Time · May 9, 2020

calicojack said:
I have not. The thought has occurred to me. Although, this is what I was thinking:

1. If there is too much head space (i.e. too loose), I would think I would get light primer strikes.

2. If it were too tight, that could certainly cause a deeper primer strike. I would think it would have trouble going into battery. Hmm - is that necessarily true?

Probably would be a good idea to get a 9mm Go gauge and see. I would have to figure out how to remove the extractor from that bolt.

I believe what happens with excessive head space is that the case is forced forced back against the bolt while the firing pin still has forward momentum.
I had the same thing happen with 1911's , both 9mm and 45acp, after the barrels were reamed a little to far. I'm talking about only .003-.005" over maximum HS.
What you need is the No-Go gauge, it will probably chamber the round when it should not.
I'm not familiar with the AR9 platform but you should be able to chamber a spent case, with the magazine removed get a feeler gauge between the bolt and he case.

If you let the chamber get really dirty the problem will gradually go away, but buy that time your firing pin could be burnt up.

calicojack · May 9, 2020

Trigger Tuner said:
I believe what happens with excessive head space is that the case is forced forced back against the bolt while the firing pin still has forward momentum.
I had the same thing happen with 1911's , both 9mm and 45acp, after the barrels were reamed a little to far. I'm talking about only .003-.005" over maximum HS.
What you need is the No-Go gauge, it will probably chamber the round when it should not.
I'm not familiar with the AR9 platform but you should be able to chamber a spent case, with the magazine removed get a feeler gauge between the bolt and he case.

If you let the chamber get really dirty the problem will gradually go away, but buy that time your firing pin could be burnt up.

I am getting both a GO and NO GO, they come as a set in this case. We shall then see where we stand.

[EDIT] This thing is brand new - if it does not head space - back goes the upper to the manufacturer.

John from MD · May 9, 2020

A Go gage is only used when you first set up headspace on a barrel. If you suspect excessive headspace, a go gage does nothing for you as the bolt will always close on it unless the barrel was improperly set in the first place and then you would have a short chamber. A short chamber can be detected by measuring the spent brass.

Punctured Primers on New AR 9 Build

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