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Old 04-21-2020, 11:43 PM   #1
usasof
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Default 107UR issues

Had a 107UR that I SBR'd and had the barrel cutback to Krink specs and a four piece Bulgy added to the front.

Just got it back and the gun will short stroke every 2-3 rounds and fail to feed!

Thoughts?

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Old 04-21-2020, 11:47 PM   #2
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There is a gas restrictor that needed to be removed.
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Old 04-22-2020, 12:02 AM   #3
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Where is the gas restrictor located? I appreciate the assistance!

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Old 04-22-2020, 12:49 AM   #4
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I’m sorry to say that the gas block needs to be pressed off to access the donut restrictor. If you aren’t tooled up to do the work you will need to go back to the smith and have him do it correctly.
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Last edited by 17 Vive liberatum 76; 04-22-2020 at 12:56 PM.
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Old 04-22-2020, 12:59 AM   #5
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Quite surprised that the AK-Smith you had the work done with did not tell you about the restrictor.
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Old 04-22-2020, 01:31 AM   #6
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You will need to press out the FS/GB combo. Once you remove the FS/GB combo, turn the FSB upside down and drill out the restrictor using a 5/32 drill bit. See photo’s below.

QUESTION: Is the gunsmith that chopped your UR barrel an AK smith? If he is, then he should know to check the the FS/GB combo for a restrictor. I’m guessing the gunsmith who worked on your UR does not have a lot of AK experience.







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Old 04-22-2020, 12:50 PM   #7
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WOW, thank you everyone! Off to my gunsmith with a big WTF!
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Old 04-22-2020, 04:00 PM   #8
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I like reading on how you guys know all this shit!
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Old 04-22-2020, 07:26 PM   #9
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Quote:
Originally Posted by usasof View Post
WOW, thank you everyone! Off to my gunsmith with a big WTF!
Let us know WTF that was all about!
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Old 04-22-2020, 07:31 PM   #10
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No surprise. ANY gunsmith can cut/crown the barrel. There are but few out there that know this weapon system in, and out.
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Old 04-22-2020, 09:31 PM   #11
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I didn't even know about the restricter.
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Old 04-23-2020, 08:18 AM   #12
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Oddly enough, apparently the restrictor isn't ALWAYS a problem. My 104UR had the restrictor left in when it got circumcised, but it still functions 100% reliably. Guess I got an extra wide hole in the restrictor?
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Old 04-23-2020, 09:43 AM   #13
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Quote:
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I didn't even know about the restricter.
Me either. I thought the restrictors were only on the 104UR. I had no idea they 107’s have them as well.
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Old 04-23-2020, 09:58 AM   #14
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If the AK (any AK) short strokes, there are only four possibilities.

1.Underpowered ammo (mostly in "reloads", factory ammo is usually up to specs)

2. Too strong recoil spring (springs get weaker, not stronger as they age, this possibility of short stroke reason is unlikely unless the weapon was "customized")

3. Gas restriction (not enough gas is the most likely culprit). Amount of gas delivered to the piston changes with the change in dwell time.

4. Tweaked receiver (rails not level, restricting carrier movement). Mostly on "home builds", and/or "bubbarized" examples.

It's all fairly easy to diagnose. Most shooters have more than one weapon in their possession, and swapping parts is the best way to diagnose (along with comparing dimensions between the receivers of the well functioning rifle).

No I am not a gunsmith, I just spent a lifetime in shooting this weapon system. My schooling on these begun at the age of 14 (military academy), and lasted for 8 years.
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Old 05-17-2020, 08:15 PM   #15
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EVERY 107 had a restrictor, not all 104's did, nor all 106's.

Good thing is, when I did all three, the gas block on the 107 tapped right off, not tight at all, I'd try myself first.
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Old 05-17-2020, 08:19 PM   #16
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Quote:
Originally Posted by Danielsand View Post
No surprise. ANY gunsmith can cut/crown the barrel. There are but few out there that know this weapon system in, and out.
IF, you didn't do the research yourself, SHAME ON YOU, its up to the person using it to understand HIS system, that way, you can tell your gunsmith EXACTLY WHAT you need done.

It took me HOURS of research, to FIND all the info before I did mine, somebody charging you 50 bucks to cut and crown is not going to invest that much time to know for sure.
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Old 05-17-2020, 08:48 PM   #17
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Quote:
Originally Posted by frick View Post
EVERY 107 had a restrictor, not all 104's did, nor all 106's.

Good thing is, when I did all three, the gas block on the 107 tapped right off, not tight at all, I'd try myself first.
I just had 2 107URs chopped by the same gunsmith. He said 1 had a restrictor, and the other didnít.
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