Ak cycling issues

[We The People Firearms]

Alright, every once in awhile I get a gun that just gets me. Used, matching numbers Polish underfolder kit, so i know at one time it actually worked (for those who are thinking gas tube/block diameter issues), at least I think it probablly worked alright. Virgin barrel, headspace checks fine many times over. Brand new ammo, used in another polish gun and worked fine.

Charged it the first couple rounds and got it hung up about a half inch from going in battery. Unloaded and worked action for awhile till smooth. Would load, but upon shooting, would eject first round, and fail to fully engage on second round. A little rubber mallet work back and forth and that problem went away. ran the drill bit through the port to make sure it wasn't plugged. Then it began short stroking. Ejecting round, but not stripping a new one offf the mag. Placed a piece of tape where bolt would need to travel to get to a fresh round, and it was making it. Tried the mag in the other gun, worked flawlessly. Taped the piston head to reduce space, no change. Changed bolt carriers, no change. Now it bagen stovepiping, or firing and only coming back 1/2 inch. When trying to pull the bolt carrier back, needed to slam the stock on something to get it to come open.

Took the dremel to the lugs, bolt carrier channels, trunnion, etc. to clean any burs up. Ran the bolt through by itself, it slides, locks up and turns out fine even with a live round put in it. Bolt carrier rides as smooth as glass by itself and with the bolt. Polished the bottom of the carrier and bolt, rails, everything. Checked the fit of the carrier and piston without the tube on and it alligns correctly.

All I can come up with is that it is somehow overgassed and is not allowing the bolt to unlock. However, I used the same exact bit that I always use and this is at least my 50-70th virgin barrel build.

Stuck on this one. Took my generator to the range so I could use the dremmel and tools, but it just got worse.

Ideas anyone? Missing something obvious? Customer build to be picked up on Tuesday.

[Redchevyman]

Did you install a new gas piston? If you did is there any wobble in the piston, it needs some to not bind up.

[Bavaria1990]

I had the EXACT same prob on my wasr. the mag release lever/catch next to the trigger guard wasn't properly spaced to keep the mag from shifting front to back (side to side doesnt matter)

magwell can be a prob

I would have never known to look at it, but my smithie fixed her for $25.
I can sed you his addy etc as he has ffl and can recieve and ship.

[nicoroshi]

Since it appears you've check most of what could be causing the issue with the rifle itself (gas piston to block clearance, rails to front trunnion interface, etc) I suggest taking a good look at the magazine, and how it sits in the mag well. Is it canted front to back? Is it high enough that the carrier/ bolt rides on or impacts the feed lips during cycle?
Are the interior rails parallel with the top rails, and correct spacing between them?
is the bolt getting cocked to the right off the ejector during forward cycle, and perhaps hanging or being slowed down on cycle?
These are the next places i would look.
Let us know what you find.

[TURBOELKY]

Sounds like you already did all the typical trouble shooting, thats weird. Im interested in your results though.
Tagged for updates.

[We The People Firearms]

Since it appears you've check most of what could be causing the issue with the rifle itself (gas piston to block clearance, rails to front trunnion interface, etc) I suggest taking a good look at the magazine, and how it sits in the mag well. Is it canted front to back? Is it high enough that the carrier/ bolt rides on or impacts the feed lips during cycle?
Are the interior rails parallel with the top rails, and correct spacing between them?
is the bolt getting cocked to the right off the ejector during forward cycle, and perhaps hanging or being slowed down on cycle?
These are the next places i would look.
Let us know what you find.

I probably should have tried single shots without the mag, but didn't think about it. I only had the one with me. The rails are completely parallel, the spacing appears to be correct, as the carrier and bolt or both together reun very smooth. Do you know the max tollerance between the inner diameter of the block and the piston head? Even if it a gas issue, it doesn't explain the practical jamming. I will go try a few single shots and some new mags. The mag seemed to be fine, but I never really looked to see if it was hagning up on it. It is a very tight fit, dimpled receiver. I'll break out the test barrel and let ya know. Thanks.

[FeuerFrei]

Can you change out the gas tube.
Leaky gas block? Powder residue on barrel near GB?
POLISH U/F 7.62X39 = .592 gb dia.
POLISH U/F 7.62X39 = 6.970 gas tube oal. Rom G are interchangeable here.
Virgin build shenanigans don't you know.

[We The People Firearms]

Yeah, this one is killing me. New mag and no mag, same problem. Fires the round, and the bolt carrier comes back approx. 1 inch and locks up. Have completely deburred and polished all lug channels, tried a different carrier, etc. I can manually place a round in the bolt, bolt inside the carrier, and run it forward. When brought back manually, there is a small hangup, but nothing a "normal" gun wouldn't push through. All I can think of is that there might be too much play in the bolt tail to carrier fit, and when under pressure from firing, it forces the lugs to cant and lock up??? Who knows. But the different carrier should have ruled that out. The headspacing is perfect. It seems like it must be a gas issue, but that doesn't solve the problem with it locking up hard just out of battery. When I first test fired it, I did get a few full ejections. I guess I'll see if I can get lucky and get a bolt laying around that headspaces right and go from there. Something keeps screaming gas problem, but I don't know......

[69Mach1]

Can a see a good pic of your rails near the front trunnion?

[We The People Firearms]

I nice piece of electrical tape wrapped around the piston head and the round almost went through the wall. So gas issue it is. Without micing (sp?) , or using my micrometer on every gas port and head in the shop, does anyone know the acceptable tollerances for each off hand? I have several extra blocks and pistons.