As others have said, it will do 3” shells.
3.5” shells are of very limited utility. The only “real” reason for 3.5’s was when we were forced to use steel shot on ducks and geese, and steel shot basically sucks at delivering consistent kills at longer ranges compared to lead.
The 500/590 specs:
http://www.mossberg.com/products/default.asp?id=5&display=specs
If you really, really, really have to have 3.5” shells, you’d best go with a Mossberg 835:
http://www.mossberg.com/products/default.asp?id=2&display=specs
BTW - if you’ve never fired a 3.5” 12ga loaded with lead shot... you might want to work your way up to it. I regularly shoot a .338 with 210 and 250gr pills... plenty of recoil that, and by comparison to the .338, a 3.5” shell out of a Mossberg 835 really makes me flinch. The 835 is a heavier gun than the 500 by a fair bit, too.
Other pump guns to consider are the Remington 870 and Ithica 37. IMO, the older Ithica 37’s were superior pump guns, slicker in action, lighter, faster-pointing.
Thanks for your input NVDave.
Yeah, I’ve fired the 3 1/2” shells, they’re a pain for sure. I was just curious as to the specs of the Mossy and picked one up this morning.
I’m mostly interested in home defense for this weapon.