Need a semi MG42 gunsmith

[FiscalJackhammer]

I have an email out to Bob Naess, and received a flat "no" in return from project guns when I contacted them. I have a semi MG42/MG3 built off German parts that I cannot get to run right. The bolt seems to hang up in a few places, and when fired will not cycle far enough back to chamber a new round. I have tried adjusting the muzzle cone to no avail. The biggest issue (I think) Is the bolt carrier is extremely tight towards the back of the receiver, to the point that to get it all the way out of the receiver I have to grab it by the rear and put quite a bit of force to pull it out. It was sold to me several months ago sight unseen, and until now I have not had an opportunity to test fire it, my fault, but here we are. Of course the gentlemen who sold it to me can no longer be reached. I don’t know enough about these guns to be comfortable messing with it much. Anyway, at this point I’m very frustrated with it and just want the thing to run. Anyone else out there that you all could recommend? Not something I would take to anyone locally. Thanks for any help!

[messerschmittfan]

Put some Prussian blue on the bolt and run it back and forth a few times to see where it is hanging up. The choice then is do you remove the metal from the bolt or the inside of the receiver. I have a semi-auto MG42 that when I got it the bolt hung up on the left rear. I did the Prussian Blue test and used a small belt sander from Harbor Freight to take just a bit off of the rail on the left side. I did that after checking to see if the receiver was bent, it was not. I have a German Army (Bundeswehr) receiver alinement kit that has paid for itself many times over. Anyway the bolt should slide/fall on its own weight when inserted from the rear (after removing the FCU/pistol grip and leaving feed cover off or up). The barrel should be in the gun. The front of the gun should be on the floor so you can drop the bolt into the receiver. The bolt should slide down the rails and lock into the barrel extension on its own weight. If not you have to remove the resistance. Once you get it right it will run like a champion. Keep in mind that it takes about 100 rounds through these guns and the MG34 to get them to run really smooth. Harry

[FiscalJackhammer]

Thanks for the reply. I would really prefer to send it off to someone who knows what they are doing, I am just not comfortable grinding away on the thing. No idea how I would check the receiver alignment. Never heard anything back from Bob Naess. Can you recommend anyone?

[FiscalJackhammer]

May have made some progress. It looks like the spring/buffer were binding in the rear. The buffer piece used to only be able to be twisted the 90 degrees for removal with the assistance of a crescent wrench (which I always thought was odd as every video I have seen it can easily be twisted by hand). Anyway, during the last removal it got jammed in the back of the receiver (no idea how) I mean really jammed, and after working it loose and reinstalling it, it now moves freely by hand like it should. Also seems like the action smoothed up as a result. So one thing off the list that had been bugging me. The bolt is still a little rough towards the rear, but I can actually pull it back all the way, and it goes home with much more authority now. Will have to go try and shoot it again in the next few days and see if she'll run.

I may also try lubricating it differently. Would tw25b be acceptable for the side rails/bolt and top cover? Up until now I have just been using CLP. Seems like something that would do better with grease/higher viscosity oil, but I haven't been able to find much info on the lubrication of one of these. I am a complete noob with these things, but reading all I can so take it easy on me

Also heard back from Bob, will take her out one more time and if it still won't run off she goes.

Thanks for any help!

[messerschmittfan]

I lube my bolts, both for the 34 and 43 by dipping them in 30 weight engine oil before installing them -- note this only on new unfired guns and for the first 50 to 100 rounds as it makes a real mess. BUT after the gun starts running smooth you clean it up and it runs great. I only use a very little of grease on the rollers afterwards. These things have to loosen up first to run right. Sorry I do not know a gunsmith that would work on it. Harry

[FiscalJackhammer]

Hey Harry, thanks for the tip! I'll take messy over not working any day. Will definitely give it a try. If it doesn't work I'll cry uncle and send her off to Bob. - David

[FiscalJackhammer]

Well took her out this morning, no joy. Tried lubricating the bolt in 30w as well. Disappointing but I'm thankful Bob Naess is willing to take a look at it. Will be sending it off to him in the next day or two.