The private investigators who were tailing the father of Scientology leader David Miscavige were carrying a shocking stash of guns and ammo, including an ominous silencer.

As TMZ reported, Ronald Miscavige -- who claims David kicked him out of the Church -- was tailed for a year-and-a-half by a father/son P.I. team. Cops arrested the father, Dwayne Powell, and found the weapons in his car.

Powell and his son claim they were hired by the Church to follow and even harass Ronald to make sure he didn't do anything to embarrass Scientology. David Miscavige denies he hired the P.I.s or even knew them.