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View Full Version : 7.62x39 Upper - Redemption?


FourLoko
05-25-2012, 4:16 PM
Since the topic of uppers in this caliber is frequent I thought I'd throw my own thread into the mix in case someone actually searches. In a few recent threads I've mentioned the problems with a 7.62x39 upper I bought and it probably served to scare some people away.

Long story short I had Failure to Feed, Misfeed and the bolt would not lock back after the last round. I guess in other terms it was short stroking. In the single shot mode the thing was very accurate which was annoying. The following is the most recent update I posted from a thread on another forum that will remain nameless. Quoting myself here:

Ok, back with an update. It might have taken a little longer than 5 minutes but it took someone who knew their stuff very little time to get the upper in working order. That someone was Harrison over at http://www.ar15performance.com/ Yes this is a plug for them even though it seems they're swamped with business and suffering from the same supply issues other builders are.

In any case, I sent an email explaining the situation and that the only part of the upper that "had his name on it" was the barrel. His first reply was to send the thing in and if I paid for return shipping he would fix it free of charge. I was amazed and excited. A little three day UPS trip to their shop and THE SAME DAY I get an email back from him telling me what was wrong, how he fixed it and that it was in working order and tested with a variety of ammo.

Long story short, the "experienced builder" who put this thing together installed the front A2 sight so that it was covering a part of the gas port. "Messed up gas port" was the last diagnosis I got after having some helpful forum members play with the upper at the range. Now I can't wait to get it back and deplete some of the ammo I've been sitting here staring at.

FourLoko
06-01-2012, 10:48 AM
Got the upper back today and slapped it on the lower I assembled last weekend. Hope to get to the range this afternoon...

dfletcher
06-01-2012, 11:22 AM
This is California - your AR must be color co-ordinated. I think it's somewhere in the AW regs on ban by configuration ...... :)

Anyway, glad it worked out. I like the X39 set up in the AR and as a casual (and cheap) AR plinker myself I think it's a great set up. I was in OR last weekend and got to use the 30 round CProducts, they worked fine.

FourLoko
06-01-2012, 11:40 AM
This is California - your AR must be color co-ordinated. I think it's somewhere in the AW regs on ban by configuration ...... :)

Anyway, glad it worked out. I like the X39 set up in the AR and as a casual (and cheap) AR plinker myself I think it's a great set up. I was in OR last weekend and got to use the 30 round CProducts, they worked fine.

The guy I bought it from had a matching A2 stock but I didn't want it. I do have some black middy handguards that were replaced by MOE on my other rifle. I was going to go full FG but changed my mind.

Have a couple of the CProducts 30s blocked to 10. Hoping for the best now.

ott1
06-01-2012, 12:21 PM
I used a Wolff reduced power buffer spring and now the 7.62x39 upper works as it should. Locks back on last round and no failure to feed issues.

FourLoko
06-01-2012, 7:18 PM
Ok, tested it again. Ran better on Wolf than Golden Tiger but still not 100%. I'd say 80-90% after testing all three mags. Only one FTF/double feed. The rest were FTF and some failure to lock back on the last round.

Worse however is that the front sight although obviously removed and re installed is still just as canted. As such, despite adjusting the rear sight (nearly) all the way it shoots 6" to the right at 25 yards.

Look for a For Sale thread shortly...

shoebox56
06-01-2012, 8:27 PM
Hypothetical question, not meant as a suggestion. Would an adjustable gas block have helped for the different qualities of 7.62x39 ammo?

(If the upper already had an adjustable gas block, please disregard my question.)

FourLoko
06-01-2012, 9:19 PM
Hypothetical question, not meant as a suggestion. Would an adjustable gas block have helped for the different qualities of 7.62x39 ammo?

(If the upper already had an adjustable gas block, please disregard my question.)

Don't think so sir. In my case the gas port issue was resulting in a failure of the bolt to fully cycle. On these FTF the primers are hit hard (and deep) they just don't seem to go bang.

FX-05 Xiuhcoatl
06-01-2012, 10:19 PM
Ok, tested it again. Ran better on Wolf than Golden Tiger but still not 100%. I'd say 80-90% after testing all three mags. Only one FTF/double feed. The rest were FTF and some failure to lock back on the last round.

Worse however is that the front sight although obviously removed and re installed is still just as canted. As such, despite adjusting the rear sight (nearly) all the way it shoots 6" to the right at 25 yards.

Look for a For Sale thread shortly...

I will keep my eyes open for this 7.62x39 upper :D
I'll post :Ivan: ahead of time

FourLoko
06-01-2012, 10:32 PM
You again! Taking and fixing all my mistakes. Trade for an SKS?

FX-05 Xiuhcoatl
06-01-2012, 10:44 PM
"one mans trash is another mans treasure", have you use brass ammo on your upper?

FourLoko
06-01-2012, 10:56 PM
I shot Yugo out of it on the test run before it was "repaired."

FX-05 Xiuhcoatl
06-01-2012, 11:17 PM
humm, all I can think of is under power ammo, yes ammo, nothing wrong with your upper I know yugo it's good ammo but not hot enought, just like ott1 post "I used a Wolff reduced power buffer spring and now the 7.62x39 upper works as it should. Locks back on last round and no failure to feed issues" under power ammo is the only thing I can think off, i had the same problem but in 5.56 DD barrel, and before I started buying all kinds of staff to fix it I started with the ammo, I just made my own ammo and load it hot and that fix the problem on mine, and the gas post on DD barrels are under size, only ammo that works on my AR is full military power ammo and commercial if I change my trigger group from Military to timney match trigger.

FX-05 Xiuhcoatl
06-01-2012, 11:25 PM
if you are using wolff extra power spring for the trigger group, that takes more force to make the BCG move back plus commercial or military buffer spring = FTF with under power ammo, it might sound dumb but untill you try a reduce buffer spring or hot 7.62x39 rounds you will never have a 100% working upper.

FourLoko
06-01-2012, 11:32 PM
The buffer spring is whatever comes in the PSA buffer tube/spring kit, nothing special. I'm no longer worried so much about function it's the stupid front sight. The feeding can be fixed.

Story of my life.

jink122
06-02-2012, 2:58 AM
get a low profile gas block and put a free float system and a front sight on it :)

Capybara
06-02-2012, 8:57 AM
Looks like you have a new unintended hobby FourLoko, dealing with that upper. Either tweaking it to work or selling it. Good luck.

swissarmyca
06-17-2012, 10:49 AM
What kind of firing pin do you have on this setup? Is it identical to a 5.56 firing pin? In my experience, 5.56 firing pins are not able to set off 7.62x39 ammo reliably especially Russian ammo. I have an mgi firing pin on mine and it is 100% on setting of Russian ammo. I use tulammo. Do note that enlarging the firing pin channel on the bolt is necessary to accommodate the larger head firing pin.

As for the ftf and lack of lock back, that sounds like a gas problem and due to the gas block being crooked, sounds like still a misalignment of the gas port. Is that gas block pinned or a screw in model? If pinned, then the barrel might not be cut correctly. I would then use a screw in gas block and adjust it to line up the gas ports. This commentary is speaking from my own experience with my 7.62 ar setup and I have experienced the same issues you have. Not any more. YMMV. Good luck.

SocomM4
06-22-2012, 5:23 PM
Pretty steep price for such a defective upper. Why didn't you just return it?

FourLoko
06-22-2012, 9:16 PM
Pretty steep price for such a defective upper. Why didn't you just return it?

I wouldn't call it defective, it just needs a bit more love. People ask more than what I'm asking for uppers that don't even include a bolt and carrier. Also, I'm entertaining offers.

Doubt the guy would have taken the upper back and I didn't consider that option until past the Paypal dispute time frame. I did let him know via email that he's full of ****.

sharxbyte
06-22-2012, 10:49 PM
Broke my bolt again Thursday :)

Knew it was going to happen. Going to order an LMT as soon as I get a paycheck and a refund. Took about 150 rounds this time.