e 3.14,
You can take turkeys with the 16, but you'll have to get them in close; say inside of 30 yds for a good chance to make a good, clean hit. Even closer is better.
The single shot make a fine turkey buster. NEF sells a barrel choked for turkey. A good friend uses one for his main turk buster. With a 3" shell of #4 hevi-shot, it'll knock'em flat at 50yds.
Finding aturkey load in 2 3/4 " 16ga might be a little tough, and pricey but not impossible. I'd say get a turkey barrel for the single shot 12, and saveup for a Win 1300.