I've been a constant user of Mossberg rifles my entire life. For my money they give you more for the money than any other brand.
I've owned the type you're talking about and I've never had firing pin trouble on a Mossberg. It may be that this partuicular rifle does break firing pins but I'd be suprised.
I'd investigate further. I had a 22 magnum "chuckster" in Mossberg and it was O.K.
I've got several of the models you speak of and no trouble.
Is it possible someone installed a home-made one?