AR firing pin retaining pin question

[Lone Ranger]

Is the AR-15 firing pin retaining pin proprietary and/or heat treated or will any similar size cotter pin be okay to use? The BCG I chose for the build came stripped.

 

[243winxb]

Look like a military spec pin is needed. https://www.thehighroad.org/index.p...ed-with-a-regular-stainless-steel-pin.450570/

 

[Blue68f100]

Don't use a cotter pin. Use the recommended harden pin. A neighbor had a primer blow and it bent the solid pin. Was lucky not to get the hot gases into his eyes. I had to do some heavy hitting with a punch to get pin.

 

[AlexanderA]

It looks like a cotter pin, but it isn't. Cotter pins are intentionally made of soft metal, so that they can be bent when installed. The proper AR pins are cheap. It's a good idea to have a couple of spares.

 

[Lone Ranger]

Thanks for the info. I appreciate the responses.

 

[a5werkes]

I use these aircraft quality cadium coated pins in AR15's & AR10 ; never had a problem. 25 cents each v. $4.00 apiece on some sites. I am not cheap, just not stupid.
Use a new one with each cleaning.

MS24665 COTTER PIN - CADMIUM PLATED from Aircraft Spruce

 

[boom boom]

Thanks for the info. I appreciate the responses.

The original firing pin retainer was a bit different but later the military switch to the cotter pin type. Check out the pictures
https://www.ar15.com/forums/ar-15/-/123-664688/&page=1
KNS makes a retro type pin
https://www.cheaperthandirt.com/pro...-replaces-standard-cotter-pin-851876003011.do

 

[dfariswheel]

The AR retainer is NOT a cotter pin.
The AR retainer is a special sized and heat treated firearms specific part designed not to bend.
An ordinary cotter pin is specifically made soft so it can be repeatedly bent.

Put a cotter pin in an AR and when you pull the bolt back or fire it the larger head of the cotter pin sticking out from the carrier will put a good gouge your upper receiver.

 

[a5werkes]

^ Yes, the need to gently shape the head of the cotter pin is obvious the moment it is inserted in the bolt. Two taps with a hammer to adjust head shape, slightly open the ends and I also
chamfer the ends for ease of installation. One can easily deform the head of a standard "hardened" AR pin as well with two taps of a hammer; in fact one can see in the 3rd photo some
metal displaced during shaping of the head......it's from my nice angle vise jaw surface, not the cotter pin. These are actually a little more
robust in diameter than standard ones. I have never had one fail; although everyone has heard anecdotes regarding "standard" AR pins failing, usually at an inconvenient moment. Then the standard failed pin has to be removed and replaced.

The obvious answer to the OP is just install a standard AR pin, done!

I am just suggesting that for those that are competent in their home shop there is a safe suitable alternative either to use in a pinch or as a matter of routine. In fact, this alternative is so inexpensive installing a new pin every time you clean you bolt for disassembly is probably better than continuing to use / reuse the same standard pin until it is observed to have failed.

To each their own.

 

[Lone Ranger]

^ Yes, the need to gently shape the head of the cotter pin is obvious the moment it is inserted in the bolt. Two taps with a hammer to adjust head shape, slightly open the ends and I also
chamfer the ends for ease of installation. One can easily deform the head of a standard "hardened" AR pin as well with two taps of a hammer; in fact one can see in the 3rd photo some
metal displaced during shaping of the head......it's from my nice angle vise jaw surface, not the cotter pin. These are actually a little more
robust in diameter than standard ones. I have never had one fail; although everyone has heard anecdotes regarding "standard" AR pins failing, usually at an inconvenient moment. Then the standard failed pin has to be removed and replaced.

The obvious answer to the OP is just install a standard AR pin, done!

I am just suggesting that for those that are competent in their home shop there is a safe suitable alternative either to use in a pinch or as a matter of routine. In fact, this alternative is so inexpensive installing a new pin every time you clean you bolt for disassembly is probably better than continuing to use / reuse the same standard pin until it is observed to have failed.

To each their own.

View attachment 786394 View attachment 786395 View attachment 786396 View attachment 786397

I will install an AR pin, however your procedure for modifying a pin is interesting given that it could be used as a backup. Any timeline with your modification as to how long the pin lasts?

 

[a5werkes]

^^As mentioned, for the AR10 I might shoot 50 - 100 long range shots (500 -900 meters) at a time, so I clean the gun as accuracy starts to fall off after ~ 100 rounds. I just put a new pin in each time as it's
inexpensive, like a bore patch when it has been soiled. For AR15 style firearms, I often shoot several hundred rounds at a time; same replacement program. I am not aware of any mil-spec replacement guidelines for replacing firing pin retaining pins based on round count, so in that instance one generally continues to employ the same part until it fails, then replace it with another mil-spec part. I prefer to avoid the unannounced "about to fail" aspect of that philosophy.

 

[dfariswheel]

The original retainer pin was discontinued and replaced because after a little firing they loosened and there was a problem with people taking the carrier out and not noticing that the pin had fallen out and was lost.
This rendered the rifle out of service until a new pin was obtained, which in combat was difficult.

The new style retainer is damaged mostly by two things....
One is on AR rifles with the Colt type commercial semi-auto bolt carrier and "stepped" hammer.
This is designed so that if the disconnector fails the stepped hammer will catch the firing pin and prevent a slam fire.
Often, people playing around with the rifle allow this to happen when closing the bolt and don't notice that the retainer is deformed by the force of the firing pin catching on the retainer.
This would be much worse if a soft cotter pin were used.

Another way the retainer is damaged is by people opening or closing the "legs" of the retainer, either because it's worn and loose, or because they have trouble getting it in place and close the legs to make it easier.
All that's really necessary to install the retainer is to rotate it as it's pressed in so the legs go in smoothly.
Most manuals specifically warn not to bend the retainer.

 

[entropy]

^^As mentioned, for the AR10 I might shoot 50 - 100 long range shots (500 -900 meters) at a time, so I clean the gun as accuracy starts to fall off after ~ 100 rounds. I just put a new pin in each time as it's
inexpensive, like a bore patch when it has been soiled. For AR15 style firearms, I often shoot several hundred rounds at a time; same replacement program. I am not aware of any mil-spec replacement guidelines for replacing firing pin retaining pins based on round count, so in that instance one generally continues to employ the same part until it fails, then replace it with another mil-spec part. I prefer to avoid the unannounced "about to fail" aspect of that philosophy.

I replaced them every year in my Arms Room, but then, Uncle Sugar was footing the bill, so my M16A1 got a new barrel every year also. (I did shoot up a LOT of 'accidentally' ordered excess ammo each range trip.... )

 

[AlexanderA]

The new style retainer is damaged mostly by two things....
One is on AR rifles with the Colt type commercial semi-auto bolt carrier and "stepped" hammer.
This is designed so that if the disconnector fails the stepped hammer will catch the firing pin and prevent a slam fire.

And then what you have is a hopeless jam, requiring disassembly of the rifle to clear.

The so-called "unshrouded" (beveled) bolt carrier and "notched" (stepped) hammer was a transitional design used by Colt in the early to mid 1970's. It was a response, apparently, to feedback from the ATF that some people were removing the disconnector and getting (sporadic) automatic fire through hammer follow-down. (It's worth noting that a small-collar firing pin must be used with this design. Otherwise -- with a standard firing pin -- the rifle will jam whether the disconnector is present or not.)

Later, with the blessing of the ATF, Colt reverted to the standard semiautomatic bolt carrier (and even later, to the FA bolt carrier) and the rounded semiautomatic hammer. Any owner of a gun with the "unshrouded" bolt carrier and "notched" hammer would be wise to replace those parts with standard parts, for the sake of reliability.

An extra firing pin retainer should be first on the list of spare parts to be carried with the rifle, along with a cam pin and firing pin. It's easily lost in field stripping. In my builds, I like to use a "stowaway" type pistol grip that's perfect for carrying such items.