RE: Which semi 12 x 3 1/2"
I like the Browning Gold 3 1/2 the best out of five that I like to recomend. Take a lok at the Beretta Xtrema, Benelli SBE, Franchi 912, and the Winchester SX2. For you intended uses I would also recommend a 3" model. In the 3" models take a look the likes of the Beretta's 390/3901/391, Benelli M1 or M2, Browning Golds, Franchi 612 or 712, Weatherby SAS, and the Winchester SX2 (3"). They offer a little less weight than their bigger brothers and will usally cycle the lighter loads better.