If I were going to use a 2 3/4 inch gun in 12 gauge for deer and I was worried about penetration, I would go with a handload of TSS in number 2 or B fine shot. A one ounce load would give you twice as many pellets as standard buckshot and you could super wad the load up so it never touched the bore. This shot will go through the deer even at long distances.
Lots of info on these loads. Here is one example. One does not need more than an ounce, maybe less due to the number of shot in the load and the penetration. This is just my opinion.
http://www.tungstensupershots.com/viewtopic.php?t=76
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