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 Repairing HWABS - MGC M4A1 Receiver Lug

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Cerwyn
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PostSubject: Repairing HWABS - MGC M4A1 Receiver Lug   Tue Feb 24, 2015 4:58 pm

Repairing HWABS - MGC M4A1 Receiver Lug

I know that I'm not alone in suffering from the Upper Receiver Locating Lug of my MGC M4 snapping off.
Since posting a Wanted Ad for a spare receiver I've received numerous messages from members complaining of the same Break.
Elsewhere here in the Forums' pages there are questions about repairing HWABS. Until now, it's been an impossible task BUT, at last, here's a very neat and tidy solution to the M4A1 problem cheers 

First off, here's the broken Lug:





Fortunately, the break itself is clean and contained within a relatively small area. I have seen some that are much worse with far more receiver damage.

I'd been in contact with a Youtube poster, Peter Simmens, about the High Performance cartridges he made for his MGC M4 . My receiver broke while testing his cartridges but it's clear that this break is an inherent fault with HWABS MGC M4s and other AR-15 based models, NOT due to the cartridge Exclamation 

Cartridge Video:-


Peter told me that he had experienced the same breakage and managed to repair it with Epoxy Resin reinforced with a metal back plate and metal strap. 
He very kindly offered to repair mine and I'm very happy with the results Very Happy 

The Epoxy Resin is UHU PLUS Endfest 300 (available in various sized packs on E-Bay)


 

The metal back plate with strap can be seen alongside and also here



The back plate is cut to fit the Receiver and makes use of a moulded hole that passes vertically through the Lug and Receiver as can be seen in the photos. A peg is fixed to the plate which is drilled and tapped to accept the metal strap retaining screw.



Thoroughly de-grease the Receiver, Lug and Metal back plate. Apply the Epoxy Resin as directed by the instructions and assemble. Wrap the metal strap tightly around the lug and fix in place wit the screw.
The Receiver was then put into a pre heated oven at 150 deg for 5 minutes to cure the Resin.
The idea of placing a plastic part lie this inside an Oven was nerve wracking I admit, but the repaired receiver was unaffected by the heat. Obviously great care is needed not to leave it in the oven for too long Exclamation 

The finished repair:-



 
 





As can be seen in the last photo above, any resin that squeezes from the mating surfaces needs to be removed and the back plate must remain flush with the Receiver to it fouling the Bolt Carrier as it travels with the Receiver and Buffer Tube.

I assembled the M4 yesterday. The Upper and Lower Receivers fit together perfectly and the Bolt Carrier travels as it should. Next step will be to Test Fire the model ....

I will follow this post up asap with details of a new Buffer made by Peter. The Buffer has a Socket Head screw set in its' centre which locates into a bored hole machined into a replacement metal plug that fits in the rear of the Bolt Carrier. 


New Buffer (Left) Bolt Carrier (Right) - Note Socket Head Screw in Buffer
 



New Buffer located in Bolt Carrier





Replacement Bolt Carrier End Plug (Left) Original (Right)





New End Plug showing Centred Recess





Replacement End Plug in Bolt Carrier







This arrangement stabilizes both Bolt Carrier and Buffer keeping them perfectly aligned and centred together as they travel along the Receiver. This stabilizing effect should reduce stress on the Lug.
The only disadvantage to this is that the Receivers cannot be opened just by removing the Take Down Pin. The end cap has to be taken off the Buffer Tube, Recoil Spring pulled out followed by the Buffer.
Then the Take Down Pin can be removed and Receivers opened as normal. A small price to pay if it reduces stress on the Lug Wink  

Interestingly, Tanio Koba's M4A1 Carbine has a very similar stabilizer. He has a nipple protruding from the rear of the Carrier 








which locates and centres into a female recess in the centre of the Buffer. 





The advantage with Tanio Koba's method is that Receivers are opened normally.


My very grateful thanks go to Peter Simmens, Thank You Very Much Very Happy

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Cerwyn

Hobby collector of Replica model guns and Militaria.
also member of Living History Reenactment Groups.


Last edited by Cerwyn on Sun Jul 16, 2017 6:04 pm; edited 8 times in total (Reason for editing : Updated using Servimg photos)
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claymore
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PostSubject: Re: Repairing HWABS - MGC M4A1 Receiver Lug   Wed Feb 25, 2015 11:50 am

This is good news Cerwyn
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Cerwyn
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PostSubject: Re: Repairing HWABS - MGC M4A1 Receiver Lug   Wed Feb 25, 2015 1:00 pm

It is indeed good news clay' Very Happy


At the very least it's got my M4 back together again and if the repair is strong enough to withstand firing it'll be Heaven sent.
There are several broken HWABS MGC M4s out there that may saved now cheers


The fact that HWABS can be bonded now might be the best news we've had for a long time.

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also member of Living History Reenactment Groups.
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PostSubject: Re: Repairing HWABS - MGC M4A1 Receiver Lug   Wed Feb 25, 2015 3:47 pm

Buffer & Bolt Carrier photos added

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PostSubject: Re: Repairing HWABS - MGC M4A1 Receiver Lug   Thu Feb 26, 2015 2:43 pm

Wow! Good news indeed!

Do you have any contact information for Peter Simmens, other than his YouTube channel? I have a slight feeling that he is german, so a direct contact would be a bit easier, methinks

Has he mentioned whether be plans to offer a 'repair kit' with the metal parts? Might turn into a gold mine for him and a blessing for a lot of modelgun fans...
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PostSubject: Re: Repairing HWABS - MGC M4A1 Receiver Lug   Thu Feb 26, 2015 3:02 pm

hkfan wrote:
Wow! Good news indeed!

Do you have any contact information for Peter Simmens, other than his YouTube channel? I have a slight feeling that he is german, so a direct contact would be a bit easier, methinks

Has he mentioned whether be plans to offer a 'repair kit' with the metal parts? Might turn into a gold mine for him and a blessing for a lot of modelgun fans...

Peter Simmens is indeed in Germany  Very Happy


Contact him via youtube first, he will then give you a direct contact.
Discussions I've had with him to date have centred around supplying .223" cartridges and Buffer kits for the MGC M4s 
However, it's worth asking him about a repair kit for this common lug problem  Very Happy

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PostSubject: Re: Repairing HWABS - MGC M4A1 Receiver Lug   Sun Mar 01, 2015 3:16 pm

Photos added, Tanio Koba Bolt Carrier / Buffer

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PostSubject: Re: Repairing HWABS - MGC M4A1 Receiver Lug   Sun Jul 16, 2017 10:36 am

All photos now on Servimg

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