I've had good luck using saddle mounts on older 870's with the metal trigger groups, but be
be cautious using them on newer 870's with the polymer trigger guards. I have had the saddle
mount pinch together the receiver sides when tightened down, causing feeding issues. I don't
know if it was just that particular gun, or if it was the plastic trigger assembly compressing that caused it, but
I didn't have any problems with the metal trigger guns and saddles. Make sure you snug up mag cap well, and don't remove barrel after sighting in or you may have a wandering poi/poa.