What happens when an AR is assembled w/o firing pin?

[ClarkEMyers]

What happens when a modern sporting rifle AR pattern rifle is assembled carefully in all respects but the firing pin is left out?

I've heard it's a bad idea and the implication was it's a pain to correct the mistake - the firing pin aligns some parts - but I've never tried it and don't know what happens.

My clear understanding and practice is that with many bolt action rifles it is a good idea to pull the striker (or striker assembly with spring or bolt sleeve) to say run ammunition through the action as before a hunting trip especially a once in a lifetime Africa or Alaska trip.

I've done it that way, or pulled the firing pin (striker) and extractor and in some cases (Remington pattern) plunger ejector to check headspace with gages. This especially with a set of headspace gages for match rifles by thousandths not just go/no go/field but to determine chamber depth or to check for a .223 chamber or a 5.56 chamber. Again almost exclusively in a bolt action. I've done it in single shots and break actions but that's trivial.

What's the story in a Modern Sporting Rifle or AR when everything is put together with no firing pin?

 

[BBBBill]

Well the firing pin passes through the bolt cam pin and keeps it aligned correctly. If the firing pin were not installed the cam pin could possibly rotate enough to jam the bolt carrier group in the upper. If you're concerned about possibly igniting a live round, why not make a bench pin by cutting off the tip of an old worn firing pin and painting a brightly colored band around it for easy identification.

 

[rcmodel]

The firing pin is all that keeps the bolt cam pin from rotating in the bolt and keeping the square head from getting turned out of alignment with the clearance cut in the left sidewall of the upper receiver.

At that point, it will be difficult if not nearly impossible to get the bolt carrier out of the upper receiver to correct it.

As BBBBill said.
You need a neutered FP in your tool shed for situations like you describe.

They make a handy dandy little 1911 pin punch too!

rc

 

[ClarkEMyers]

That's a useful suggestion thanks.

The other issue with AR pattern firing pins is doing an AR and a 1911 at the same time with the firing pin used as a tool on the 1911 then put back in the rifle. This has actually caused some in-service failures. A dedicated AR15 firing pin in the range bag for a 1911 tool is a handy thing.

Truth is this (along with a Glock with a hammer) is an issue John Ringo trivialized with his Black Tide Rising series. A fun read but Mad Mike who I think cares about getting guns right out of respect for his readers or self respect or both is about the only current writer (Donald Hamilton always got it right) in that field who doesn't ruin my enjoyment needlessly.

 

[Jim K]

I feel really ignorant and benighted. I never thought of tearing down one weapon to use the parts to tear down another one, then forgetting to put the all the parts back in. But then I am not up on the latest gunsmithing techniques.

Jim

 

[herrwalther]

I was in a situation assembling an AR back together after cleaning where the firing pin was misplaced. Because of time constraints, I had to finish assembling the AR without the firing pin until it was found/replaced. The pin was found a couple hours later. The AR was no more easier or harder to dismantle to add the missing part. I may have just lucked out since I did not charge the AR during that time to perform a function check, which would have rotated the cam pin. So I would not recommend having something there.

 

[Jackal]

What happens when a modern sporting rifle AR pattern rifle is assembled carefully in all respects but the firing pin is left out?

It wont shoot....