Weld up reciever or use a 80%?

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Weld up reciever or use a 80%?

Postby Patracy » Tue Sep 05, 2017 9:39 am

I'm in the planning stages of a MG42 build. I haven't decided if I'm going to do a full on postie or just a semi. I've been looking at a few options for kits out there. I've found one source of kits that has a complete matching set of receiver parts to do a total weld up. From what I gather, people pretty much use a section of unistrut as a jig to weld them in. My question is, what's the best option? Buying a cheaper parts kit that only has the front section of the gun with a barrel and using a 80% for the rear. Or buying the "complete" kit I've found that also will need rails and a barrel. From what I've gathered, they all end up a wash when it comes to total price.

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Der Alder
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Re: Weld up reciever or use a 80%?

Postby Der Alder » Tue Sep 05, 2017 8:39 pm

IMO its easier to buy a kit that has the front shroud section cut off as long possible in the rear like Centerfire has (usually with the front rail and recuperator holes), this way you can square it up in the rear past the camming piece area (saves from camming piece fitting), then use an 80% receiver like a GM or BRP and square to match. which is easier to make straight and to correct length rather than piecing a torch cut receiver back together and keep it straight. Either way can be done as many threads here explain, but this to me this way is easier with the garage tools I have (Dremel, wire welder, hand files, etc)..

If you want to take another big short cut you can then splice on a squared up RTG rear MG3 stub which saves you the buffer tab hassle. Many of the torch cut full receivers are cut through the buffer tabs anyway. Keep in mind you will need a MG3 buffer and buttstock which looks much better IMO and if you go this route and you may as well install a MG3 recuperator being the buffer tabs are cut for it. If your length is correct (measure from the rear of the camming window to the rear of the receiver) as per German manual your recuperator will be correct (fore to aft) as well which is another plus.

I've only built using 80%'s BTW. I've never used a jig to try to align...if you make sure you are square and straight and put a piece of threaded rod through it to hold it together and 'stitch weld' it should stay straight if you are careful. But if its not straight before welding its not going to be after. If you do it this way you are re-welding in essence a '3 cut saw cut' rather than an angled torch cut which again is much easier IMO. '3 cut' meaning the front bushing splice/rear shroud to receiver splice and or rear MG3 stub splice. All of which should be squared. I work front to back BTW.

Just like too IMO its easy to take a M53 shroud that has the barrel bushing cut off, square the front of the shroud to length, then weld an RTG/MG3 front bushing back on to correct length; instead of cutting the whole front off and replacing it like some of the angled torch cut kits require.

Also get the RTG 'new' MG3 rails that are not drilled, then once aligned drill them and the receiver rather than trying to match up existing holes in a torch cut receiver. RTG also has the used MG3 ratchet plates...I recently bought 2 and both are nice. This saves you from trying to patch a cut up one back together and they have the handle slot already cut in them... something many newly made ones lack.

Biggest thing is keeping it all straight and as close to spec length as possible. You can sometimes be off 'a little' in one area without issues... problems later arise are when you are off in several places because of stacked tolerances.

This is what has worked well for me, others may differ....

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Re: Weld up reciever or use a 80%?

Postby rodom » Mon Sep 25, 2017 8:22 pm

I'll take a minute and second Der Alder's opinion. He was of great assistance to me during my build, and I posted most of the build here to the website. Following his advice, I used an 80% rear section and a MG3 buffer section from RTG. It's a little more welding but it saves so much work.
It worked out well for me, as my semi unit has been fired many times without a hitch. You can find everything you need to know about building a legal semi automatic MG42/MG3 or M53 here in the builds featured on this website. And good luck to you.

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