Remington makes a few versions of their semiautos for HD, 3-gun, and LE markets. The designs started out as hunting shotguns, sure, but there have been 1100 and 11-87 defensive shotguns for many years, so it's not true that these are just hunting guns.
11-87 Special Run 18.5"
http://www.remington.com/products/firearms/special_runs/model_11-87_sportsman.asp
1100 Tactical 18.5" Speedfeed and 22"
http://www.remington.com/products/firearms/shotguns/tactical_shotgun_specs.asp
11-87P 18.5" and Class III 14" Parkerized
http://www.remingtonle.com/shotguns/1187.htm
They have tube magazines, which can be topped off easily. They don't, of course, have detachable box mags. On the other hand, you can't really top off a detachable box mag, so you're limited to the number of mags you own and carry, rather than how many shells you can grab from your pocket or a drawer.
What's cool about the Remingtons? With proper maintenance, they're VERY reliable, proven designs (1100 is 43 this year). They point quickly, like a bird gun, which is a good thing. Finally, I have an old hunting 12 Gauge 1100 with a hard plastic buttplate, and it has nearly zero recoil or muzzle flip. Multiple shots on target are easy, smooth and painless.
Other semiautos that cross the hunting/HD divide are Benellis. They recoil harder than the Remington gas guns, and they're expensive, but they're a great design. Definitely worth a look.