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Discussion Starter · #1 ·
I put a 7.62X39 upper on a regular AR lower and I'm having a little trouble with it shooting steel cased ammo. I've read as much as I want to about why it will not shoot consistently. I have installed a stronger hammer spring. I even chucked the firing pin in a drill and took a little off the FP stop. I have an enhanced firing pin on order.
One thing that gets me is if I push the forward assist in before I fire the rifle it shoots more times than not. I thought it could head spacing but when I talked to the local gunsmith he said it was probably not that since it would not fire if that was the case.
So...could it be that the buffer and spring are not correct for this round (the lower came form a 5.56)?
 

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Like I said above, if I push the assist forward it will shoot more times than not. This is when I shoot steel cased ammo. I'm thinking that the bolt is not going all the way forward into battery.
Would a heavier buffer or stronger spring be the cure?
You won't know until you try. It makes sense.

I have always wondered how an AR can RELIABLY generate enough gas pressure in the chamber to match the bolt momentum of an AK. Stripping the round from an AK mag ALONE requires more force. (I don't know if your AR uses AK mags) It stands to reason to try adjusting the gas system. I would defer to someone who did it on their 7.62x39 AR.
 

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Is this a fairly new upper and BCG failure to return to battery may be do to parts not being "broken in" for lack of a better term.
Also if it is new the BCG should be lubed until you think it has too much then put on a little more.
Using a heavier buffer with low power steel case ammo could possibly lead you into a whole new set of problems. If I would change anything it would be to a stronger buffer spring. I wouldn't do that unless you have a few hundred rounds through it.


Sent from a phone I can use to do my taxes, but can't make a damn call.
 

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I built my 7.62x 39 and never had issues. I used an extra heavy hammer spring, and a Colt firing pin. I didn't modify my firing pin in anyway. The Colt firing pin mic's out a hair longer than standard. I run Frankenmags mags, they are AK mags welded onto a AR mag sleeve that fits in the magwell. I'm running a carbine gas system, with a standard H buffer. I've put over 5k rounds in it now, and never had any issues. It will chew anything I put in it, and have 0.0 issues. My questions to you are:

What gas length are you running
What buffer
What BCG
What barrel
What mags


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I bought the upper in used condition at a local gun show. I was told it was made by Double Star.
The magizines are 7.62X39 ASC (20 round).
The lower I built for a 5.56.

Beautiful rifle you have there BTY.

Those mags caused me problems. I tried ASC, C-Products, and even the old Bushy's. Nothing worked right until the Frankenmags. I assume the BCG is also double star, not too sure about the quality of those BCG's. I used a SOTA Arms barrel and bolt, and just got a stripped carrier to pop the the bolt in. I'm always weary of gunshow deals people come across. The vendors piece together whatever makes them the most profit, which generally means sub-par parts. I would also check the chamber of the barrel extension, I've seen shady manufacturers actually coat the chambers and cause a smaller Internal diameter. I had a friend that came to me with a Stoner barrel and it was completely coated in the chamber and couldn't even chamber a round. We had to send it back. Also what weight is the. Under and what length has are you running. That could also be an issue.
 

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In order!
1. Magazine Issue (Try a good quality magazine)
2. Ammunition which could be out of spec and improperly sized or OAL.
(Try other good quality ammunition!)
3. Steel Case ammunition with "Varnish" building up in the chamber.
4. Be sure the locking area of the Chamber (Barrel Extension area) is clear of debris and dirt.
5. D Ring used over the Extractor & Spring when not needed.
*I doubt very much if it has anything to do with the Buffer Spring and Buffer.
Or Headspace. I would bet on one of the above
 

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I do not have a 7.62 x 39 Ar but I have 2 223 Ar 15s and some bolt action 762 but I have always heard brass is better to shoot. An Ar does not like shooting steel casings i don't even shoot steel casings in my 7.62x54r Mosin
 

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Discussion Starter · #17 ·
Ok, I understand it shoots brass better , but do you have any issues at all with shooting brass. If you shoot 300 rounds of brass how often are you failing with brass. I'm trying to understand wether it is the ammo or something else.
Yes, I do have issues with the brass cases. They shoot at a better rate than steel. Like I said, if you push the forward assist forward before you fire a steel cased round it shoots more times than not.
 

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If brass is doing it as well than here is something else wrong. Again , what gas length and weight buffer are you running. As for the rifle failing, what exactly is it doing , failure to feed, failure to eject, failure to fire?
 

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Wolff heavy hammer spring with the enhanced firing pin will help fix your problem.

Pure, he's already done that. I'm trying to figure out the rest of his configuration. I'm guessing he's running a carbine gas system with and not sure of the buffer weight. He's saying that if he taps the forward assist , he has better luck. Not sure if it chambering. I told him to check his chamber. I've seen shady manufacturers coat the chamber causing the internal diameters to be off. That would explain why steel is worse than brass. He's having problems with brass as well. Sounds like a failure to feed issue. Not getting the right answers out of him.
 
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