Just to completely confuse everything, I'd like to suggest either:

FNH SLP

Fastest semi-auto shotgun around and it works better than most with many lower power loads.

Or

KelTec KSG

Yes, its a KelTec! But its short, has room for a ton of shells, and the newer iterations of it are pretty reliable as long as you shuck that pump action all the way.

Both brands have outstanding warranties much like Busse.