I built an ‘AR-47’ (AR-15 7.62×39) a few months ago with a Bear Creek Arsenal Side Charging Upper and a Palmetto State Armory Multi-Caliber Lower and just this last week had the ability to fire it.
The gun and magazine cycled the rounds, however every other round or even 2/3 rounds I had a light strike on the primers and failures to fire.
I was using Tula steel cased, Red Army Standard and some Chinese ammo, all which had light primer strikes. All the ammo, even the light struck ammo, fired in my AK and SKS.
I figured the Palmetto State Multi-Caliber lower would have the correct springs to set off the primers in 7.62x39 ammo. Anyone had any similar issues or any advice? Is the issue with the FCG or the Upper? Please let me know, as I love the way the rifle is configured.
You’ll need a heavier hammer spring and/or make sure you have an enhanced firing pin for the harder primers in the ammo you’re using.
Yeah the lower says multi caliber, but that’s more for legal reasons since it can take uppers of different calibers. It doesn’t mean the internal parts are 100% compatible with all calibers or ammo. All manufacturers do that actually, if it included non standard or upgraded parts it would be advertised that way. It’s never good to shop based on assumptions.
Thanks for letting me know about the hammer springs and the intricate legalities of the firearm lower manufacturing industry. The ability of the AR-15 lowers to take upper receivers of different calibers is an interesting concept; I will have to spend more time and dive into such fascinating ideas. And finally thank you for the advice that ‘It’s never a good idea to shop based on assumptions’. I will make sure to tattoo that on my forearm for future reference.
Make sure you installed the hammer spring correctly. Putting it on the hammer backwards will create light primmer strikes. With combloc ammo, the primers are harder, hence the randomness of what is going on.
Thanks man, great advice! Will do!
LW, while this problem is new-to-you, light prime strikes are not a new problem on 7.62x39 conversions.
If you do a google search, you might read that standard firing pin length has been a problem.
As MrFister mentioned above, an enhanced firing pin may be a solution to your problem.
I have never had trouble from a PSA upper or lower but BCA uppers may need some work or improvements/enhancements from their owners to improve function & accuracy.
Best of luck with your new “Carolina” rifle!
I love it… but you should definitely contact BCA, just recently they have upgraded their bolt carriers, extractors and firing pins in all their 762 uppers. I don’t believe the PSA lower is the problem. in reading your post its says you started your build a few months ago, BCA just released this upgrade last week they have a video on their website…hope this helps maybe you can send yours back and they will upgrade yours