AR type 7.62x39 bolt and firing questions

Shazam

Shazam

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Hi CGN,

I hope that this is in the right section. I have an AR pattern 7.62x39 bolt and Having light primer strikes.

MRA 7.62x39 bolt - they don’t sell or make a specific firing pin for this as they mill standard Milspec bolts. If one uses a standard 5.56 firing pin it doesn’t like hard primers.

I was able to get a BCL 7.62x39 AR firing pin from SFRC (quick shipping!). However the new firing pins diameter is a tad thicker than the 5.56. This makes sense to address hard primers, and it’s a fraction of a bit longer as well. I don’t want to risk the potential of slam fires or any other ND.

Now: before ai go ahead and bore out my bolt face, has anyone had similar issues with the 7.62x39 bolt/firing pin?

I’ve reached out to BCL to see if they sell a dedicated bolt in 7.62x39. That maybe the best.

Any feedback would be appreciated!






BCL 7.62x39 firing pin:

overall length 80.83mm
Pin diameter -0.30mm


Standard 5.56 firing pin:

Overall length 80.25mm
Pin diameter -0.45mm
 
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You may want to ask someone who has both a .223 and a 7.62x39 MCR what the physical diffences are between the bolts and firing pins on their rifles.
 
I used a honing stone for sharpening knives and honed the back end of the bolt where the firing pin collar bottoms out against. By doing this you can retake 5 or 10 though off the back and will allow the pin to protrude a little more. With this modification you can use any AR15 firing pin from here on out. Simple and cheap.
 
Thanks. I have a feeling that it’s larger/longer for a reason (surplus ammo)

I don’t have access to a 7.62x39 MCR but I will check against the CMMG Mk47 firing pin (however they re-engineered their BCG). That rifle just east any ammo!

This build is for an LPC straight pull and I want to reduce the light strikes on surplus ammo
 
mac100 said:
I used a honing stone for sharpening knives and honed the back end of the bolt where the firing pin collar bottoms out against. By doing this you can retake 5 or 10 though off the back and will allow the pin to protrude a little more. With this modification you can use any AR15 firing pin from here on out. Simple and cheap.
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This is great. However the pin doesn’t protrude through the 5.56 pin hole of the bolt
 
Get an enhanced firing pin. This is a delicate situation so only use the EFP with surplus Ammo and not reloads or quality brass Factory cartridges which have normally seated primers.
 
Yes. This is a delicate situation as I want to ensure safety. There are commercially available 7.62x39 enhanced firing pins designed. The US manufactures won’t ship to Canada. And no one retailers appear to have any?

The BCL firing pin that I just received has different specs (it may have been manufactured by NEA). It doesn’t fit the standard mil spec firing pin hole in the bolt face. So I wanted to reach out in case others have had this issue? If anyone knows of a 7.62x39 bolt and pin to recommend (that’s available). That would be great.







place image over image
 
a firing pin with a larger diameter will spread the same amount of force (from the hammer spring) over a larger area giving you even lighter primer strikes, the real solution here is a more powerful spring and maybe more pin protrusion as previously mentioned.

BCL is not known for actually solving problems.
 
xeelee said:
Have you tried emailing True North Arms...I know they are out of stock at the moment but you might want to check when they are available again https://truenortharms.com/ar15_default_store_view/7-62x39-firing-pin.html Also, a place called Sportque use to carry Windam Weaponry 7.62x39 enchanced pins.
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Yes it seems TNA was out of stock.
I emailed the Big US manufacturer of enhanced firing pins and they don’t ship here.

I spoke to a tech at MRA today. They didn’t have recommended for their 7.62x39 AR bolt.
I got a response from BCL and hoping that they have info for why their products isn’t spec, or if it needs a dedicated BCL bolt.

I’m sure that there are good options. Just not easily available.
Im was at gunsmith today and he offered to work the firing pin to spec (and leaving the additional length for pertrusion with harder steel cased surplus primers.
 
Have you tried emailing the guys at SBI? I know they put out some pics of 7.62x39 mm builds on their Instagram page.
 
Shazam said:
This is great. However the pin doesn’t protrude through the 5.56 pin hole of the bolt
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Just use a 556 firing pin and this way you don’t need all these enhanced ones. You can tune it to exactly what you need. I have had the same problem that you have had and have done 4 of these with repeatable success.
I wouldn’t go any other route as this is as simple as it can get.
 
mac100 said:
Just use a 556 firing pin and this way you don’t need all these enhanced ones. You can tune it to exactly what you need. I have had the same problem that you have had and have done 4 of these with repeatable success.
I wouldn’t go any other route as this is as simple as it can get.
Click to expand...

Thanks for this. Maybe a stronger hammer spring?
 
Shazam said:
Thanks for this. Maybe a stronger hammer spring?
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You can also just put a slight bend on the hammer spring ends which will make it striker harder. The trade off is that the trigger will gain extra pull weight. Honing the back of the bolt is the way to go. You can push the firing pin through the hole and measure the protrusion and keep honing until you get what you need. Cost=$0 for al, of this
 
mac100 said:
You can also just put a slight bend on the hammer spring ends which will make it striker harder. The trade off is that the trigger will gain extra pull weight. Honing the back of the bolt is the way to go. You can push the firing pin through the hole and measure the protrusion and keep honing until you get what you need. Cost=$0 for al, of this
Click to expand...

Thanks for this!
 
I have a 5.56 pin and it works just fine for 7.62 ammo. if you have a lot of lite primer strikes may be check if spring is installed right in a trigger.
 
I put a little extra bend on my USGI hammer spring today and shot 80 rounds of Barnaul with no light strikes. My trigger was already pretty heavy to start with so I didn't notice any increase in pull weight.
 
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