why crushed case mouths...

[no guns here]

My unit went to fire at a German range Saturday.  We were trying to qualify for the German Schuetzenschnur or "german shooting badge" as we call it.  I didn't know that we still got medal's for shooting germans but that's a different story...  So my question is... why does the MG3 machine gun crush the mouth of all the spent brass???  Any ideas?  My guess is to keep the brass from being easily reused but that's just my guess.


NGH

[Questor]

How are they crushed? From the mouth toward the primer or with the mouth crushed closed as if by pliers?

Do you have a picture? That may help with a diagnosis.

My first guess is that the cartridges are longer or shorter than the original spec for that gun.

[no guns here]

Sorry, no pics.  It was in one place on the mouth.  Crushed in like something hit it.  Wasn't smashed all the way across or anything like that.  Picture taking a case and putting a really dull chisel on the side of the case mouth and giving it a whack with a small hammer.  Extended about 1/4 to 3/8's of an inch down the neck.  I checked all four MG3's... all the cases were the same.  Obviously it was a feature designed in... I just don't know why.

Great gun though... Hitler's Bonesaw was the direct ancestor of the new one.  Most of the design is still the same.  Changed from 8x57 to 7.62 and a slower rate of fire is about all.  The German crew was able to fire, change barrels and re-engage in less than 5 seconds...  impressive to me.  According to the German Regimental Sergeant Major, Omaha beach was defended by just 6 of those machine guns.  Of course there was a crap load of heavier guns targeting that beach AND a bunch of Mausers...


NGH

[Lloyd Smale]

violent ejection or an out of ajustment ejector will sometimes cause this. I had a cetme that dented case mouths all the time and also a 3220 rossi that would do it. There was nothing i could do with the cetme. Hard ejection is just part of the design but the rossi was fixed by adjusting the ejector.

[S.S.]

some G3s will do it as will the HK91.
I hardly ever find the brass anyway because it throws them
with considerable force, and a considerable distance.

[Arier Blut]

The rollers on the bolt are out of spec. Larger rollers can be installed which get it back in timing. The first sign is usually more recoil to the shooter. As the parts wear more and more, the buffer or bolt can be damaged. Some bolts are actually out of spec, milled too much on the face. If larger rollers wont fix the issue, it generally has  too short of a bolt. Since the cetme and g3 were spawned off of the concept of the mg 42 bolt, as the other gent stated they can have similar problems.