Extended Firing Pin for AR-15 Ignition Woes

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The AR platform has become ubiquitous, with examples available in pistol and rifle form and in a seemingly growing number of chamberings. The most popular chambering is, of course, 223 Remington or 5.56 NATO.

While I don’t envision the 223/5.56 ever being supplanted as the king of the AR cartridges, thanks to the influx over 35 years of once-inexpensive steel-cased 7.62×39 ammunition along with SKS and AK rifles and now pistols from China, the former Soviet Union and Com Bloc countries, and domestic manufacturers, the AR has long been offered in models and barreled uppers chambered for that versatile round.

Even before the ammunition panic induced by Covid-19 and the 2020 election politics, firearms enthusiasts looking to save money would purchase and shoot relatively inexpensive steel-cased ammunition from Wolf and the various "Bear" brands of both 223 The increase in length is about 0.012". and 7.62×39.

In some cases, shooters have experienced problems with steel-cased ammunition ranging from stuck cases, weak extraction and ejection, unburned grains of powder, hard primers, or primers seated deeper than customary in U. S. ammunition. Recently, two acquaintances approached me a few weeks apart with identical problems. Both had purchased quantities of steel-cased 223 ammunition, the "Golden Tiger" brand manufactured by the Amur Cartridge Plant- Vympel in Russia.

Speaking parenthetically for a moment, it is recognized that many manufacturers of ARs and AR barrels recommend against the use of steel-cased ammunition due to potential problems with case sticking and reliability. The modulus of elasticity of soft steel for deep drawing is indeed different than that of cartridge brass and that does affect how steel cased ammunition expands against the chamber, how much it expands permanently, and for how long it expands elastically.

Therefore I won’t get into a debate here about one’s choice to use steel-cased ammunition in ARs. Suffice to say that these two gentlemen were handed lemons and I wanted to help them make lemonade. The complaint was that their ARs would not ignite the ammunition reliably. They wanted to install higher-force hammer springs because they both read on the Interwebz (there it is!) that stronger hammer springs were one way to fix it.

These are two different gentlemen who likely don’t know each other with nearly identical stories. I told them that hammer force is but one possible corrective action but the problem needed to be better defined. Requesting some ammo from the first friend along with his AR, the rifle was examined. It was clean, properly lubricated, and the fire control group was properly installed.

Firing pin protrusion checked out with a military firing pin protrusion gauge (part 7799735) and measured exactly 0.031" with a digital depth gauge, well within the standard specification range of 0.028" minimum and 0.038" max. Federal XM193 cartridges fired 30

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for 30 without issue. Primer seating depth ranged between 0.002" and 0.004" below the case head. On the other hand, the steel-cased Vympel Golden Tiger ammunition had a seating depth between 0.0045" and 0.0075". Roughly half of the Golden Tiger failed to fire. It was confirmed that the firing pin was made of steel and not titanium. Titanium pins are significantly lighter than steel firing pins, the touted advantage being faster lock time.

The trade-off can be erratic ignition because of the lighter firing pin, unless a higherforce hammer spring is installed. Some imported steel case ammunition has been reported to have military-grade hard primers to resist accidental discharge from bolts slamming shut when chambering around. It is quite possible that primer cup thickness or hardness were contributing factors but I had no means of measuring this variable to confirm it due to Berdan primers in the ammo.

They are difficult to remove without damage and the proper equipment like a hydraulic punch, and measuring fired primers is invalid due to the change in the primer cup from the firing pin indent.

After a consult with some friends who are serious AR fans whom I knew to run steel case ammunition in their rifles and pistols, I discovered that inconsistent ignition was somewhat of Break open the rifle by pushing the rear takedown pin to the right, rotate the two receivers apart, pull out the charging handle part way, and withdraw the bolt carrier. a known problem with ARs chambered in 7.62×39 and less so for those guns chambered in 5.56/223.

Stronger hammer springs did work in some cases but the most reliable fix was an extended-tip firing pin. American Gunsmith Reader Services 1.

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Extended firing pins for ARs have identical or slightly similar parabolically-shaped tips compared to those of standard AR firing pins, except the length of the tip "body" is approximately 0.012" longer, depending on manufacturer or sales outlet literature. This slight bit of lengthening is represented as being sufficient to account for the increased primer depth and/or harder military-spec primer cups found in steel cased ammunition, but the increased length is said to not cause pierced primers.

After consulting with the first acquaintance, I suggested we try an extended firing pin and received his approval. An Enhanced Firing Pin was ordered from Black Rifle Arms (BlackRifleArms.com, BRA Enhanced Firing Pins are primarily intended for 5.45×39 or 7.62×39 ammunition. The label on the firing pin received states, "AR- 15 Firing Pin 7.62×39/5.45×39 Enhanced Firing Pin". On BRA’s current website there are two distinct item numbers, one for the 5.45×39 cartridge and one for the 7.62×39.

It is suggested to call or email Black Rifle Arms to discuss your particular needs for an extended firing pin, particularly if 5.56 ammunition is involved. There is also a customer review on the BRA website mentioning Golden Tiger 223 having a 40% failure to ignite rate prior to installation of a BRA Enhanced Firing Pin and 100% ignition following 130 rounds fired without a primer piercing. Many readers are familiar with basic field stripping of an AR but I’ll cover the basic steps anyway.

First, remove any magazine, retract the charging handle, and confirm that the chamber is empty. Leaving the hammer cocked, push the rear disassembly pin out to the right and open the rifle like a double barrel shotgun. Pull back the charging handle slightly and grasp the rear of the bolt carrier, then withdraw the bolt carrier assembly fully from the upper receiver. With the bolt carrier on the bench, use a hook or needle nosed pliers to pull the firing pin retaining pin from the left side of the carrier.

Pull the firing pin to the rear and down to remove it. Set that firing pin aside and take up the extended firing pin. Apply a drop or two of your preferred lubricant to its shaft. Insert the extended firing pin into the bolt carrier and replace the firing pin retainer pin. Replace the carrier assembly in the upper receiver, seat the charging handle forward, rotate the receivers closed, and push the rear takedown pin home.

Tip protrusion with the enhanced firing pin installed measured 0.042", 0.004" in excess of the upper specification limit. I wasn’t concerned about that amount of excess because it was sort of the point of the exercise, wasn’t it? Further, the firing pin protrusion of my Mossberg MVP Patrol in 5.56 measured 0.049" and it hasn’t punctured a single primer in nearly 300 rounds.

I gathered up the customer’s cranky Golden Tiger ammunition along with some surplus South African M193 and commercial 223 of my own to try it out. Two 30-round magazines were filled with each of the three types of cartridges for a total of 180 rounds. The rifle was secured in a home-built wood rifle vise with elevated saddles which was clamped to the shooting bench. The vise saddle elevation allows for installing 30-round magazines in ARs and AKs, and 35-round magazines in Galil rifles for test firing.

I fashioned a brass catcher using a plastic tarp and squeeze clamps. Equipped with safety glasses and hearing protection, I stood to the side and used a 1/2" diameter 30" long dowel to trip the AR’s trigger. The result? Success on two fronts. First, the cranky Vympel Golden Tiger steel-cased ammunition touched off 60 for 60 with nice primer indents and no piercings. The South African M193 also ran 60 for 60 without piercing, as did the Federal American Eagle rounds.

The indents in the M193 and Federal AE were visibly deeper than if fired with a standard firing pin, but there was no sign of partial piercing such as black smudging in the dimple or soot radiating away from the dimple on the primer cup. The BRA Enhanced Firing Pin was an effective solution for my one acquaintance’s problem of what to do with 3,000 rounds of steel-cased ammunition with very spotty ignition. The second acquaintance hadn’t invested so deeply into his lot of hard-primered 5.56.

When he purchased a BRA Enhanced Firing Pin directly and installed it himself, his experience with faultless ignition and no pierced primers mirrored mine. What’s more, the extended firing pin is an easily reversible solution if a shooter chooses to switch back to ammo with softer primer cups as a safety measure to avoid the potential for pierced primers. AG