Public Service Safety Message - Firing Pin Block

[bj139]

Did you ever cycle live rounds through your AR and notice little dimples in the primers?
Did you ever think how your day could be ruined by a single slam fire.
I bought an extra firing pin to grind the tip down but micro seconds before, my brain kicked into gear.
I thought, why not prevent the pin from sticking through the bolt face by blocking a standard firing pin.
A single #6 washer placed in front of the firing pin appears to do the trick.
I haven't tested it fully, as in pulling the trigger on a live round in the house but I fed rounds through and no dimples.
If this prevents a single slam fire my job will be done.
DICLAIMER: DO NOT TRY THIS WITH LIVE AMMO. DEMONSTRATION PUPOSES ONLY. YOU ARE RESPONSIBLE FOR SAFETY TESTING.
Just don't forget to remove it if you need it to fire at a later time.

[BluntForceTrauma]

Dude, you WIN . . . something! Excellent idea. Let us know once you test it fully.

[bj139]

Thanks, BFT. Sometimes good ideas are mixed in with the unusual ones.
Dare I try to drop the hammer in the house? I better wait till I get to the range.
Some one will try it before I do since I can't step out the back door for a go.
If anyone tries it post here.
I am not sure how to prevent leaving it in place and a home defense situation or hunting trip goes wrong.
I will think about that.

I now have a lot of washers in case I want to build something else.

[imaguy3]

I guess I don't understand the purpose? Why would anyone be cycling live rounds just to cycle live rounds? Buy or make dummy rounds.

The design of the AR is a floating firing pin. As soon as you close the bolt on a live round you get a dimple b/c the pin has come forward and tapped it, however it lacks the energy needed to detonate the firing pin. Once the hammer strikes the firing pin is when the proper amount of energy is transferred to cause it to fire. The a slam fire can occur is if the firing pin is physically stuck in the protruding position and the mass of the carrier coming home gives plenty of energy. The hammer could also follow the carrier down which could also cause the gun to fire, but again... all these are major malfunctions.

If you have to go to all the trouble of taking the assembly apart to place your block in place, and then put it back together when you want to shoot; why not just take the firing pin out, do what you need to do, and then put it backin ? You can insert a BCG minus firing pin and do all the test cycling you need to do without issue.

[bj139]

I guess I don't understand the purpose? Why would anyone be cycling live rounds just to cycle live rounds? Buy or make dummy rounds.

The design of the AR is a floating firing pin. As soon as you close the bolt on a live round you get a dimple b/c the pin has come forward and tapped it, however it lacks the energy needed to detonate the firing pin. Once the hammer strikes the firing pin is when the proper amount of energy is transferred to cause it to fire. The a slam fire can occur is if the firing pin is physically stuck in the protruding position and the mass of the carrier coming home gives plenty of energy. The hammer could also follow the carrier down which could also cause the gun to fire, but again... all these are major malfunctions.

If you have to go to all the trouble of taking the assembly apart to place your block in place, and then put it back together when you want to shoot; why not just take the firing pin out, do what you need to do, and then put it backin ? You can insert a BCG minus firing pin and do all the test cycling you need to do without issue.

I know the firing pin holds the cam pin in place. I had never considered the loose parts might work OK. Did you try this?
If the cam pin turns while the bolt is closed does it jam the BCG into the upper?

[imaguy3]

If you're holding the gun right side up. I don't see how it can come out at all. Gravity and tight tolerances b/t the receiver and cam pin will hold it in place just like the firing pin. Yesterday actually a coworker inadvertently put their bcg in the gun after maintenance, cycled it, and had no issues before realizing the firing pin was still on the bench.

I"ll be home in a cple hours and test it on my own gun, videotaped, if you'd like before trying it on yours.

[bj139]

I just removed the firing pin completely and fed some rounds. The bolt got hung up a few times and I had to work it to get it loose.
Every time I removed the bolt the cam pin was perpendicular to the correct direction.
I had the fear I might have a permanent BCG upper assembly jammed in place.
Feeding had many jams.
When I put the firing pin in with the washer there was one jam.
I don't believe a loose cam pin can be used to test reliabilty in feeding.
The bag of washers was $1.28. I can afford that.

[imaguy3]

so back to my other question. Why not make some dummy rounds? You could make some even without loading equipment. Pull some bullets (using pliers or a vice), dump the powder, put the bullets in some previously fired cases with some super glue to keep them in place. You can make your primed cases inert by filling with water to soak the primer.

Heck I have a few bullets on the bench I can send you if you'd like.

[bj139]

I could load some dummy rounds in brass cases which would not last long upon repeated chambering in a AR.
Why didn't I grind the end of the firing pin off is a good question as well.
I did run a file over the end and with the chrome plating it did not bite.
There are often many ways to accomplish an objective.
This is just one of them; an inexpensive one. I don't see the problem.

[A5BLASTER]

Nice thinking out the box sir.

[HuntTXhogs]

I’ve had a slam fire before , at the range thankfully... more on that in a bit.

I once cycled the bcg without a firing pin in the bolt - was test cycling to check rounds feeding from mag lip mods and thought I was being super safe by removing the firing pin altogether. Well this resulted in a serious lockup of the internals and I soon figured out the firing pin keeps things aligned and must be installed.

The slam fire : I had read about slam fires occurring more often when rounds are loaded by hand , singularly into the chamber, and the BCG sent to battery from bolt lock open. I do load single rounds when guns give me cyclic issues or when load developing (rules out BCG effect when stripping rounds from mag). Anyhow the full weight of a bcg hittinf a stationary / captured round was enough to go boom. I’m sure the original design didn’t test for this and I’m thankful I learned my lesson without hurting anybody.

So what I do now.

Takes just as long as the washer hack might and requires full strip and reassembly of BCG but basically I just cut the tip off a firing pin and use that one to test cycle rounds.

Stay safe

[Sticks]

I can see the wisdom in this, and I can also see the potential for problems.

Complacency is the problem.

By simply following the basic 4 rules of gun safety, you will never have a problem. As soon as you introduce live ammo into the equation at home you have put yourself and those nearby at risk.

Did I really put the washer on the firing pin?

Did I really remove the washer from the firing pin?

I like the innovation, but I'll continue to test with dummy cases that are primer-less, and marked as such with a sharpie. Federal cases are ideal for this as they are worthless for reloading. Even Hornady cases if they get trashed are not much of a worry. They are a consumable. The bullet that gets chewed up - Load it into a live round and get rid of it the fun way the next time at the range. Maybe learn how much a marred bullet actually has an effect on your accuracy.

I'm not so stingy or broke that a $.70 ($.40 brass, $.30 bullet) dummy round will ruin me.

[bj139]

I have AR uppers in 9 different cartridges. I am running out of fingers.
I don't have time to be making all those dummy rounds since I would need about 10 of each to test full magazine conditions.
I am sure many here have cycled live ammo through firearms to test fit.
This just makes it safer.

HuntTXhogs, I had a slam fire at the range as well with a 458 SOCOM under the same conditions you described; full slam on chambered cartridge.
I stopped doing that at home, figuring that magazine feeding would slow down the bolt to avoid slam fire.
But I was still a little worried because of the dimpled primers.
I wish there was a way of blocking the firing pin without disassembly but if there is I don't know it.
Anyway, I can only suggest ideas and others are free to use them or not as they see fit.

Sticks,
Did I really put the washer on the firing pin?

Did I really remove the washer from the firing pin?

With the BCG out of the upper, push the bolt into the carrier and push the firing pin forward, simultaneously.
If the pin is sticking out, there is no washer. If not, there is a washer. Simple.

[SightedIn]

Its an innovative idea...but theres no way im cycling live rounds through my firearm at home...maybe the range

[bj139]

I posted this on ar15armory dot com and got a lot of bad comments.
The mod said it was unsafe and finally deleted it.
I don't think they got the idea.

[montana]

Military-style semi-auto rifles seldom have firing pin retraction springs. If care is not used in assembling ammunition, a “slam-fire” can occur before the bolt locks. The military arsenals accomplish this using different techniques and components—including different primer sensitivity specifications—from their commercial counterparts. CCI makes rifle primers for commercial sale that matches military sensitivity specs that reduce the chance of a slam-fire when other factors go out of control. If you’re reloading for a military semi-auto, look to CCI Military primers.

Effective slam-fire prevention requires more than special primers. Headspace, chamber condition, firing pin shape and protrusion, bolt velocity, cartridge case condition, and other factors can affect slam-fire potential.https://www.brownells.com/reloading/prim...79079.aspx

I copied this from the above link.

This is why the imported Galils and some AK rifles from China had firing pin springs. Most commercial spec primers have thinner cups and are more sensitive, which can result in a slam fire when cycling a fresh cartridge.

[bj139]

Military-style semi-auto rifles seldom have firing pin retraction springs. If care is not used in assembling ammunition, a “slam-fire” can occur before the bolt locks. The military arsenals accomplish this using different techniques and components—including different primer sensitivity specifications—from their commercial counterparts. CCI makes rifle primers for commercial sale that matches military sensitivity specs that reduce the chance of a slam-fire when other factors go out of control. If you’re reloading for a military semi-auto, look to CCI Military primers.

Effective slam-fire prevention requires more than special primers. Headspace, chamber condition, firing pin shape and protrusion, bolt velocity, cartridge case condition, and other factors can affect slam-fire potential.https://www.brownells.com/reloading/prim...79079.aspx

I copied this from the above link.

Hi montana,
This post was really more about safety in testing feeding and extraction which I am sure you knew.

The point about harder primers is well taken in normal operation.
I had to get a higher power hammer spring to reduce misfires when shooting 7.62x39 steel cased ammo.
I doubt they could slam fire. They are hard primers.

[grayfox]

For safety and testing as Bj writes, why not simply remove the firing pin and retainer, bcg will cycle just fine without it, right? ..... pretty easy to see/check if you're ready to fire, pull the bcg and look for the pin/no pin.
Or maybe I'm missing a bigger point.... this way sounds pretty straight forward.

[montana]

Hi montana,
This post was really more about safety in testing feeding and extraction which I am sure you knew.

The point about harder primers is well taken in normal operation.
I had to get a higher power hammer spring to reduce misfires when shooting 7.62x39 steel cased ammo.
I doubt they could slam fire. They are hard primers.

I guess I'm a little confused. For testing, just make up some dummy rounds or purchase a spare firing pin and grind it down https://www.stagarms.com/firing-pin/ otherwise just take the bolt carrier out if a person is concerned about someone chambering a round indoors. Function testing in doors with live rounds makes no sense to me IMO.

[SDW]

I guess I'm a little confused. For testing, just make up some dummy rounds or purchase a spare firing pin and grind it down https://www.stagarms.com/firing-pin/ otherwise just take the bolt carrier out if a person is concerned about someone chambering a round indoors. Function testing in doors with live rounds makes no sense to me IMO.

I was thinking A) When can I get them in Titanium or carbon fiber (kidding of course) Or B) Why not make a few dummy rounds.