wojtowicza,

Had the exact problem with a Mooseburg about 20yrs ago. It cost me the shot of a life time on a drive at a 12pnt buck at 20yrds. I was not a happy camper and will never forget that lost shot. It was the friggin cheap plastic safety as jp4 mentioned. Had it replaced by gunsmith. He installed steel version. I still have that gun and another Mooseburg 500. Both have taken about 40 deer.