I just got for FREE from Mossberg fiber optic snap-on sights (front & rear) my 835 is old and only had the front white bead sight. Anyway, these sights are suppose to be simple, just snap them on, but they won't snap on, they are made from aluminum or some sort of metal, I don't want to crack the plastic fiber optic. I called Mossberg and asked if the vent rib is adifferent size from 11 years ago compared to today's 835, they said no. Anyone have any clue how I can get them on without breaking?