G&g mp5 gearbox - anti reversal latches

[Egon_247]

Hi all. 

My boys beloved mp5 has developed an issue. He was going for a bit more power in the shape of a new spring and found my random collection of springs. One seems to have damaged the gearbox by way of the anti reversal latch Mounting hole...it's now oval 😳

As this isn't a rotating part, could I rebuild it with chemical metal around this point?

At first I thought it was just the latch being crap but it's making odd noises after cycling. Like it's pushing backwards.

It's the electric blow back and other than a new gearbox case I'm struggling to think how to fix it....

Any ideas chaps/chapesses?

[Speedbird_666]

  On 02/04/2023 at 21:03, Egon_247 said:

As this isn't a rotating part, could I rebuild it with chemical metal around this point?

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Worth a punt - I would try to fill with JB weld or similar and then re-drill the hole. Not sure how long it would last as a fix though - whilst it doesn't rotate more than 45 degress, the ARL is under (shear?) load which is probably why the hole distorted in the first place.

 

Replacement shells can be found here:

https://www.fire-support.co.uk/product/gg-version-2-gearbox-case-blow-back-version

 

The G&G Blowback Gearboxes are notoriously poor for longevity. Whacking a higher power spring into one is a recipe for trouble - there's a good chance of cracking the entire front off, or at least cracking around air transfer hole to the pneumatic piston. I would be sticking with M95/100 springs and looking into other guns if higher performance is required.

 

 

 

[Rogerborg]

JB Weld is decent stuff, and may adhere and hold up to the strain, but - depending on how much meat is around the hole - I'd be looking at drilling it bigger and putting a bushing in. How's your parts pile sorted for those?  

[Colin Allen]

  On 03/04/2023 at 07:27, Speedbird_666 said:

 

Worth a punt - I would try to fill with JB weld or similar and then re-drill the hole. Not sure how long it would last as a fix though - whilst it doesn't rotate more than 45 degress, the ARL is under (shear?) load which is probably why the hole distorted in the first place.

 

Replacement shells can be found here:

https://www.fire-support.co.uk/product/gg-version-2-gearbox-case-blow-back-version

 

The G&G Blowback Gearboxes are notoriously poor for longevity. Whacking a higher power spring into one is a recipe for trouble - there's a good chance of cracking the entire front off, or at least cracking around air transfer hole to the pneumatic piston. I would be sticking with M95/100 springs and looking into other guns if higher performance is required.

 

 

 

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Or replace the gearbox with a non-blowback one.

[Speedbird_666]

  On 03/04/2023 at 08:36, Colin Allen said:

Or replace the gearbox with a non-blowback one.

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I would normally suggest that for an M4 variant, but I'm not sure how the MP5 mock bolt could be fitted (and still move with the charging handle) as it's directly mounted to the Blowback Piston.

 

 

 

 

[Colin Allen]

  On 03/04/2023 at 08:48, Speedbird_666 said:

 

I would normally suggest that for an M4 variant, but I'm not sure how the MP5 mock bolt could be fitted (and still move with the charging handle) as it's directly mounted to the Blowback Piston.

 

 

 

 

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Ah, bugger!

[Egon_247]

Yeah, looks like it's new shell time. I'll give the jb stuff a punt but I'm not holding my breath. 

I've gotta make up a spring tester as I'm sure one of them is an m120. Which without short stroking, would probably be the culprit... Damn thing could do with a quick change spring too, you gotta strip the box each time!!

It's a nice pew but like you guys have said, after a google or ten,they do have cracking issues.

 

[Egon_247]

Ok, "dad tech" to the rescue!! Lol

Stripped it out last night and the arl spring was mullered, so a bit of pliers action and it was back to the shape it should be. Ish.

Used a bit of jb on the hole and it's back up and running, 12rps at 260fps/0.28g. yay.

Thanks for the help and suggestions guys, appreciated. 👍

(Then fixed his Glock 19 as his recoil spring was in back to front and the slide was sticking!!!)

[Colin Allen]

  On 04/04/2023 at 11:26, Egon_247 said:

Ok, "dad tech" to the rescue!! Lol

Stripped it out last night and the arl spring was mullered, so a bit of pliers action and it was back to the shape it should be. Ish.

Used a bit of jb on the hole and it's back up and running, 12rps at 260fps/0.28g. yay.

Thanks for the help and suggestions guys, appreciated. 👍

(Then fixed his Glock 19 as his recoil spring was in back to front and the slide was sticking!!!)

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Well played!  I will be interested to know how long the JB Weld fix lasts.

[Egon_247]

Still going....😁