Cool, the Wingmaster is an excellent choice. But still...LOL...I would buy two guns. Only because the rifled barrel w/ scope mount is going to cost you between $225 - $300 (crazy, isn't it??). The Express barrel is $225 and the standard is $300. So, it's like you could have a whole other gun for about the same amount of money.
http://www.cabelas.com/cabelas/en/te....form23&Go.x=0
The H&R slug gun really is an excellent gun...look up the reviews. For $250, I'd buy that over a spare barrel any day. Of course, I'd prefer the Marlin or the Savage, but your tacking on a little extra $$ there.