I am currently finishing up a semi auto MG 42. This has been a real challenging build as there was not a lot of detailde information available when I started and had to work out most of the build myself. to further complicate matters the semi conversion was not really reliable and even the $5k+ guns from BRP don't work reliably with all ammo types. After a couple of months of R & D and lots of testing I have gotten a working gun that shoots all types of .308 and 8mm ammo reliably. The changes were to the semi conversion to the bolt and the gripstick.
Basically the BRP conversion uses aan AR 15 FCG which is not up to the task at hand. the 2 peoblems being failure to fire and blown primers with boxer primed ammo. Basically I felt that the AR fcg was designed for a small rifle primer and the hammer and hammer spring were not up to holding the firing pin in place causing blown primers, and failures to fire.
My solution was to find another fcg that was designrd for large rifle primers and had a strong hammer spring. After looking at several fcg's I settled on the FAL parts. After buildinf a test setup the FAL parts worked very well and solved the primer and FTF problems.
The second problem was the firing pin, I made and tested several pins and increaset the pin diameter to 3/16" to have a more ridgid pin. This improved ignition but caused other problems with binding that caused slam fires. This was corrected by using the original mg42 firing pin and making a striker. the new setup has been thouroughly tested with almost 800 rounds of both .308 and 8mm ammo of different types.
All the parts were designed to be simple, reliable and doable by the average home builder without a machine shop.
The build is basically a 3 step process:
1. Reconstructing the receiver, modifying it to semi configuration and installing the rails. this is a days worth of TIG welding and grinding. a simple alignment jig can be made for a few dollars.
2. modifying the gripstick, this consists of making and installing sideplates in the gripstick and a hammer tube stop and trigger return spring retainer. some grinding and reshaping of the FAL hammer is also required.
Modifying the bolt, requires drilling the bolt wedge and feed stud, making a striker and making and welding on a bolt extension.
This project will cost from about $700.00 to $1,000.00 depending on where you get your parts and how much of the work you do yourself since a BRP semi costs over $5.000.00 it is a worth while build, to say notheing of the WOW factor. I will be supplying a kit of conversion parts and possibly doing some of the bolt and gripstick work.
Basically to get started you need a kit with a rebuildable receiver. there are several suppliers of kits all have advantages and disadvantages.
there are 3 types of guns, mg42 in 8mm, M53 yugos in 8mm and mg3 kits in .308. If tou get an 8mm gun you only need a feed cover, feed tray and bbl to convert to .308.
If you get a .308 gun you will need a bbl, feed tray, feed cover, recouperator and booster cone.
Most of the parts are readily available from several sources, the only problem part is the bbls. they all were bought up when the bbl ban hit.
Since this is a complex gun I would strongly recommend getting the best parts to eliminate problems from worn out parts, in the long run a good kit will save you money.
There are 2 types of receivers available, 3 cuts and 4 cuts, the 3 cuts being less work to reconstruct. the only source for 3 cuts is Angola Armoury, Dan is currently out of receivers but will have more available in January along with kits
Kits are available with 4 cut receivers from IO quality varries, there are some currently on sale, for $399.00 these are listed as .308 yugo M53 kits they also have 8mm kits for more money.
Century has 8mm Yugo kits with no receivers for $350.00
BRP may have more German mg42 kits coming but they do not have the rear part of the receiver.
I will start moving a copy of my build tutorial over here this weekend.