While there is no way to set headspacing on the 42, it is VERY important. Not all bolt/barrel combinations will headspace correctly together. You need to check headspace to make sure the combination(s) you have work OK. I have 5 barrels and 3 bolts. All but one combination headspace OK, and one combination is too tight. Blowing the barrel change door open is not a fun thing, and bulging the receiver or picking brass out of your arm is really embarrassing.
The 1919 does not fire at 25 shots per second, so 50 year old ammo having a 1/10th of a second handfire will blow the crap out of an MG42. People blow up $12,000 1919s too running cheap ammo. It just doesn't happen as often due to the rate of fire, and the fact that the 1919 is built from considerably heavier steel. For semi guns, a slight hangfire is not a problem.
Let's be realistic here, running 50 year old ammo in a $40,000 gun because it's cheap is like putting diesel fuel in your Ferrari. It'll run for a while, then bad things happen. If you want to shoot it cheap, convert it to .308 and it's only $180 per thousand rounds or so. BLowing up a 42 is a lot more expensive than the small change you're saving on 50 year old ammo.
Was your 42 running erratic before it blew? Did it run a little faster then a little slower? That's a split second hang fire. The old corrosive ammo can also eat the casing from the inside, leaving it weak. The steel cased ammo is notorious for this. That's undetectable from the outside.
I have some old ammo that I shoot in my 98k rifles. The worst I've had is a 7 second hang fire. Really scary (Try a different word.). I found that by shaking the cartridge before using it in the rifle, I can hear the powder rattle in some cartridges, and not in some others. The ammo that didn't rattle I pulled the bullet out, and dumped the powder into a bowl. It was stuck together with mold.... little hairs held the powder in clumps. THAT's a hangfire waiting to happen, and a 42 is not very forgiving with 9 cent a shot ammo. If it leaves the bullet in the barrel because of a semi-dud, the next shot blows up. I don't run diesel fuel in my old RoadRunner, and I don't use 50 year old ammo in a $40,000 gun.
Buy a set of headspace guages. 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. I will presume you're running the bolt catch in the bolt. If you're not, then this is part of why the guns blow up. The bolt catch is MANDATORY, not just recommended for full auto. WIth the semi guns, holding the locking rollers tight to prevent a bolt bounce is not a problem. If you've ever struck steel with a hammer and had it bounce, this is what happens with the bolt face and rollers when they hit the barrel extension. The bolt catch prevents, or at least minimizes this. Do the math: At 25 shots a second, the bolt is completely closed for less than 1/100th of a second. It spends almost 1/50th of a second recoiling, then another 1/50th of a second going forward. The bolt is only locked up for a VERY brief split second. It doesn't take much of a screw up with junk ammo to embarrass the shooter.
I've found that the cheapest and safest way to shoot 8mm is to reload it. The MG42 sings a little better song with 8mm than it does .308, but .308 is still cheaper to buy than 8mm is to reload, so I usually run .308 myself. The 42 with .308 still runs like a scalded dog, but I know the difference because I heard it and shot it.
Last edited by jbaum
on Thu Jun 16, 2005 5:37 pm, edited 1 time in total.