Not always true. My NIB 870 that I bought a couple years ago jammed like a MF'r. Seems that Remington got a little carried away with that shitty coating they're putting on their newer firearms, and caked the chamber full of that shit.
You'd fire a round. It'd expand, per the norm. Then it'd get stuck from the overly tight chamber. You'd have to slam the butt on the ground to dislodge the shell.
It was an easy fix with some steel wool and a dowel rod, but it should never have happened in the first place.
My Mossy 500, on the other hand, has been flawless.
Both work wonderfully now, and I'd recommend either to anybody. I have the silly habit of completely tearing apart every weapon I buy to tinker with it. I usually do a trigger job while I'm in there, and fix any factory fuck-ups, along with whatever else I find necessary.