Part of owning and shooting firearms is the process of troubleshooting and fixing issues that arise “along the way”. I recently had an issue with my Palmetto State Armory KS-47 Hybrid AR chambered in 7.62x39mm– but nothing that couldn’t be easily fixed! This is the story of how I got this rifle “back in action”.
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KS-47 8.5″ 7.62x39mm Pistol Overview
From the Palmetto State Armory product page:
The Palmetto State Armory KS-47 G2 is based on the AR-15 and combines the modular construction, accuracy, and precision of the AR platform with the stopping power and the magazine options of the AK. The KS-47 G2 lets the AK shooter capitalize on their inventory of AK magazines and AK ammo with an AR-style platform. Unlike the AK, where the barrel is permanently pressed into the receiver, the KS-47 G2 features an AR-style modular configuration which consists of a barreled upper receiver, and a lower receiver that houses the fire control group and magazine. The modular configuration allows customers to have several different barrel configurations with one lower receiver, just by releasing two pins.
Barrel Length: 10.5″
Barrel Profile: Heavy
Barrel Steel: 4150
Barrel Finish: Nitride
Chrome Lining: No
Muzzle Thread: 5/8-24
Twist Rate: 1 in 10″
Barrel Extension: KS47 Gen2 Single-Large Feed Ramp
Gas System Length: Pistol-Length
Diameter at Gas Block: .750″
Gas Block Type: Low Profile
Muzzle Device: A2-Style
Receiver Material: Forged 7075 T6
Receiver Type: KS-47
Handguard Type: PSA 7″ Lightweight M-Lok Free Float Rail
Bolt Steel: 9310
Bolt Carrier Profile: Semi-Auto
Fire Control Group: PSA Enhanced Polished Trigger (EPT)
Grip: Magpul Grip, Black
Brace: SBA3 Adjustable Pistol Brace
Buffer Tube Length: Carbine
Buffer Tube Diameter: Mil-spec
One day, I grabbed the KS-47 to test out some subsonic handloads and ran into an issue straight away. The first round fired just fine, but the second round failed to fire. I ejected the live round and noticed NOTHING on the primer. Not a light strike, nothing. I hadn’t seen this issue with the KS-47 up until this point, very strange.
I tried a couple more rounds, and had the same thing happen as the second round from the initial problem: nothing on the primer. The gun wouldn’t fire at this point at all.
Finding and Correcting the issue
Since there was no firing pin depression on the primer, I decided to look at the firing pin and bolt/carrier assembly first. When I took things apart it looked as if the firing pin wasn’t quite in place correctly. So I decided to compare the firing pin to another I had from another AR-15.
Above you can see a clear difference between the two firing pins! I was thinking about retention and noticed that the flanges on the firing pins looked very different in diameter. Here’s what some measurement determined:
- KS-47 Firing pin keeper flange diameter: 0.3085″
- Sharps AR-15 firing pin keeper flange diameter: 0.372″
So I thought I would try the Sharps firing pin in the KS-47. BOOM! Problem solved!
I looked up the dimensions for the AR-15 firing pin, and found this print from Survival Monkey:
Sure enough, this print calls for 0.328″ for that flange. It appears that the factory KS-47 firing pin was out of spec from what I can tell.
Black Rifle Arms 7.62x39mm AR Firing Pin
While investigating a replacement for the firing pin, I quickly discovered the fact that 7.62x39mm firing pins are “custom” for the AR-15 platform allowing better primer ignition for scenarios like running 7.62x39mm steel-cased ammunition. I found that Black Rifle Arms has a great stainless firing pin for this application, and it cost just over $10.00. Not bad!
From the Black Rifle Arms product page:
Enhanced Firing Pins Are Engineered to Maintain Mil-Spec Characteristic Where the Firing Pin Interfaces Inside the Bolt and Still Allow Greater Protrusion Into the Primer.
Stainless Steel for Superior Corrosion Resistance Properties.
Enhanced Firing Pin is Specifically Designed For Use with Steel Cased Ammunition.
Helps to Ensure Positive Ignition on Notoriously Steel Case Hardened Primers.
ENHANCED FIRING SPECIFICALLY DESIGNED FOR USE IN THE:
This firing pin installed smoothly, and has performed very well in my testing so far. Problem solved!
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