While some of the converted bolt action Mausers can be quite good, others can be downright dangerous.
The locking lugs have been ground down or even ground off the bolt heads to accomodate the head of a shotshell and the only thing locking the bolt is the bolt handle notch and maybe 1/8" of bolt head lug surface.
Done correctly, this is adequate for light shotshell loads, done poorly and,,,,
Remeber also that many or most of these guns were originally barrelled and reamed for European 2" or 2.5" shells, not 2.75" American standard shells and were also proofed for very light 7/8 ounce to maximum 1 1/8 ounce loads.
Many were reamed to 2.75" here in the states but that does not make them safe for heavy field loads and especially not for steel shot loadings.
Keep this in mind before you consider buying one of these old guns as a shooter.