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DrAlexanderTobacco

LCT RPK - fell apart mid-game!

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Or post-game, at least.

 

Hi guys - Interesting problem with my LCT RPK-74M, essentially the front-end (everything from the rear sight block to the flash hider) ones to slide forward out of the gun, in one piece. I've done nothing that should have caused this, can't think of any specific rough action.

 

I've taken a look at the exploded diagram that LCT provide, and it doesn't quite match up to how I see people disassemble similar rifles (LCT made) on Youtube - hopefully people here can confirm the best path forward, because there's only one possible location I could see that's possibly missing something:

 

image.png.0ce44abf6ae628792d02faa4f6835656.png

 

The circled hole seems like it should hold a screw or a pin, as I've seen disassembly vids for LCT include taking out the sight as seen then unscrewing whatever's in there.

 

Compared to the below diagram, however, I can't seem to match up a pin.

image.png.747d63cee077e069e3f39d7e2e15be5b.png

 

Have I got the complete wrong end of the stick here? Anywhere else I should look for something rogue that's broken off? 

 

Thanks!

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Under the rear sight block, in the front trunnion there are two set screws - you can see them in the exploded diagram as SC0AK-SET0AA-6.

One of the MAJOR weaknesses of the LCT AK series is that these two tiny set screws are the ONLY thing holding the front end on, as you've discovered.

Check they aren't missing (They should be M3 grub screws, approx 6mm long) but the only real fix here is either to loctite them and check them every game or to drill out the holes and tap them for M4 grub screws and put some of them in to make it extra secure.

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Just now, DarkLite said:

Under the rear sight block, in the front trunnion there are two set screws - you can see them in the exploded diagram as SC0AK-SET0AA-6.

One of the MAJOR weaknesses of the LCT AK series is that these two tiny set screws are the ONLY thing holding the front end on, as you've discovered.

Check they aren't missing (They should be M3 grub screws, approx 6mm long) but the only real fix here is either to loctite them and check them every game or to drill out the holes and tap them for M4 grub screws and put some of them in to make it extra secure.

Makes total sense - thanks very much! I can see the part you mean now. I'm guessing they're missing because there's no rattle or otherwise, they're just... not there - but an easy fix so TYVM.

More frustrating perhaps is how the front reciprocating forwards/backwards frayed the wires. I'll replace those too.

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What Darklite said, plus be careful to not let them strip.  Whoever put my RPK model together stripped the most awkward to get to one of the two, and thus I cannot ever take mine apart to change inner barrel.  Prying the gearbox out is another frustrating matter, which I get to experience again soon (changing wire harness out like others to a better set with deans hopefully).

The RPK models are usually the most susceptible from what I have read over the years.  Oddly enough because of my predicament I kinda wish I had your problem. :D

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Supplementary question; I've taken another look, finally, and can see that both screws seem to be secure within the bracket they screw into:

 

image.png.b175e0e53664084e77f4d976cdbbd066.png

 

Poor photo, but you can see the two screws (marked SC0AK-SET0AA-6) in the centre. 

What I'm confused by at this stage is how the front end is secured by these screws; am I missing one? I can't see how they're responsible for securing the front end.

I can try to get a video of the front end sliding forwards and backwards, if that would make it clearer.

 

Edit: Looking at it further there's a circular shaped mark on the outer barrel, visible above both grub screws - thinking the screws might need to dig in there maybe aka be tightened. Will play around to see what happens.

 

Edit 2: Looks like those indents on the OB are actually the other half of the grub screws... I'm guessing they've been shorn off due to misuse. Could someone confirm? If so looks like I'm drilling them out to tap for 4mm :)

Edited by DrAlexanderTobacco

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50 minutes ago, DarkLite said:

Yup, that's where the grub screws lock the barrel into the front trunnion.

Thanks - Considering the various other things I had planned for this and a relative lack of time/enthusiasm to do carry them out myself, I'll prob be in contact this/next month to ask you to take a look and a few of your services offered on your website - stay tuned :D

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 I suggest you drill some small holes for the grub screws to sit in. That way, even if they become untight they'll still hold the front and you'll notice the movement before it all falls apart.

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15 hours ago, DrAlexanderTobacco said:

Thanks - Considering the various other things I had planned for this and a relative lack of time/enthusiasm to do carry them out myself, I'll prob be in contact this/next month to ask you to take a look and a few of your services offered on your website - stay tuned :D

No problem mate! Fire me an email when you want to move forward.

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Is it a weird idea to try and thread the chamber side of the barrel with a big wide thread so the grubscrews can grip into that?

Sent from my H8324 using Tapatalk

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52 minutes ago, Lone_Bullet said:

Is it a weird idea to try and thread the chamber side of the barrel with a big wide thread so the grubscrews can grip into that?

Sent from my H8324 using Tapatalk
 

No. Actually I posted that solution two days ago, just without threading. A hole for them to go in would suffice.

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