BDog,
And all others concerned. If I were to make a guess, I'd say that there is a good chance that the Mauser in question is a Spanish M1916. Bent bolt handle? Short stock with a straight grip? Dead givaway is the 'M1916' near the muzzle!...
Anyway, I have one of these, and have a similar gripe. Mine is that with the bolt closed, striker cocked, and safety on, there is visible vertical movement of the rear if the bolt (Bolt shroud) when the trigger is pulled. Putting the safety on fire doesn't release the striker, but there is still vertical movement of the rear portion of the bolt as the trigger is moved to the rear. Total movement is no more than a few 16th's - but any movement at all is VERY disconcerting.
I've yet to fire this weapon, and hesitate to do so at all. I've yet to have it headspaced, but even then I have to question the current chambering of this piece.
The Rifle started life as a Spanish Mauser M1893 - chambered in 7x57 (7mm Mauser). Max pressure for this cartidge is in the 40's, something like 47,000 c.u.p., although don't quote me here, I don't have my reference in front of me! Somewhere along the line, someone in Spanish ordnance thought to upgrade these and had them rechambered/rebarreled in a 30 caliber offering. This cartidge is/was 7.62 CETME, to which I understand is a dead ringer for 7.62 NATO (.308 Win) with one BIG exception. It doesn't develope the same chamber pressures as the 308, although it is higher then the 7x57.
Then there is also the information that the Spanish Mausers were notoriously soft in their receivers, which would make any conscientious rifleman nervous!
So... if you couple the above mentioned fact with the fact that you are attempting to fire cartridges that are almost 10,000 c.u.p. over what the receiver was designed for, you might just see the conditions that we are starting to see.
To my way of thinking, it's a plain shame if these weapons are unsalvagable. I'd like mine back in the original caliber (7x57) or maybe a .257 Roberts. But if the reciever shows signs of setback, then I think I have a new wallhanger.
I don't know if rebarreling would fix this, and of course, that would have to be determined by a competent 'smith. But I don't feel (at all) confident with touching this piece off, and I would caution anyone who owns one of these to have it thoroughly checked before you start banging away with it. Better safe then sorry!
In case you are wondering, I got a lot of the info that I have about this from Jerry Kuhnhausen's Mauser book.
Good luck, U.G.