The Model 12 was initially offered in 20 gauge only, which made it the first Winchester shotgun of that gauge and the first hammerless slide-action repeating shotgun to bear the Winchester logo.

For much of its production run, the Winchester Model 12 was the repeating shotgun by which all others were judged.

The Model 12 was offered in multiple gauges. In fact, the first Model 12s to hit the market were 20-gauge guns although 12- and 16-gauge offerings came out in 1913 and the 28-gauge debuted in 1934.