jbaum wrote:As I too have said before, messerschmittfan is absolutely correct. This problems is caused by the back of the chamber being drilled out and missing.
I am not talking about MG3 barrel anymore, I am talking about my green mountain 8mm barrel that has identical chamber to my original Yugo, so that is not the issue.
For setting headspace on both my MG34's and MG42's I use the standard 7.92x57mm go/no-go gauges, if I remember correctly I purchased them off eBay a few years ago.
go no go gauges mean nothing on mg42 but you guys keep talking about it like it is a must. It actually can be bad on MG42 because perfect headspace on the gauge may be too tight for MG42. Go no go gauge is something you must use on bolt action rifles or on firearms that has the action hidden where you can't physically inspect the chamber, but in MG42 you take out the extractor and you can pretty much use live round, I got some aluminum tape that is 0.10mm thick, so I can use that to measure exactly how much slack I need to have but if I don't have good combination to compare to then I can ask you guys for help, but if you are not willing to help fellow MGer then all I can do is guess work.
Here an old thread where some guy had similar problems but worse than me. viewtopic.php?t=453
here is what Jbaum wrote then:
If the rollers won't lock up fully with the GO guage in the chamber, try a different combination of bolt and barrel. Check the length of the ammo, and compare it to the longest guage that the rollers will lock up with. This is done out of the gun, with the bolt and barrel sitting on a table. Make sure the locking rollers extend completely to the outside of the grooves. You can remove the firing pin and try it with a live round if you like. A little loose on headspace seems to make no difference. A little too tight and the rollers don't lock completely and the base of the cartridge blows off from lack of support. A LOT too tight, and the cartridge blows off the back, and can destroy the receiver.
Here is my green mountain barrel combo with 1973 Romanian round inside, with bolt fully locked I get '0' clearance between the round and bolt face, if I pull on the bolt I get 0.50mm slack and only slack is in the rollers vs. cam grooves. Can someone do the same test I did? I actually may have a bit tight headspace and may have slight out of full lock firing once things get hot.
Ok so I did another test with the spent shell that has the most pronounced ring and found out that the rollers do not fully lock with this shell. This indicates that my 8mm shells show out of the full lock firing. Now I really wonder it head space is too tight