I have seen a lot of frustrating slug guns, and all have been pumps. Newer Ithaca guns notwithstanding, this is just the wrong system to select for a slug gun.

Bolt guns made like rifles are the way to go. I have a bolt action Marlin 512 that shoots very good groups with a couple brands of sabot slugs. 3" at 100 yds is typical. That's all I need for deer hunting. Used bolt actions like this or the Mossberg 695 (I think) can be had if you look, for not much money. If I had to buy a new slug gun it would be the Savage in 12 Ga. Browning is making their bolt action slug gun again too, but they are pricey.

Why a guy would limit himself to a single shot gun, either slug gun or muzzleloader, is beyond me. We all try to put the first one where it needs to go, but things do happen that can make a quick second shot a blessing. I'd hate to be in need of a quick second shot in regular firearm season, standing there trying to reload a muzzleloader (which I can do in about 30 seconds), while a wounded deer moves out of sight. An unnecessary tracking job is just that.

I do like to hunt with a muzzleloader, in muzzleloader season.