Sorry for the thread drift...
The Remington 11-48 (Sportsman 48, Mohawk 48 etc) was a streamlined receiver long recoil action semiautomatic shotgun that evolved from the Browning A5 clone, the old 'humpback' Remington Model 11. The 870 is a pump.
The 3-shot Model 11 was the first Sportsman model- it was factory limited to a fixed 2-shot magazine, for 3 rounds total. I don't know if the Model 48 Sportsman was a 3-shot magazine or not.
Remington started using the term Sportsman before WW2 to describe a limited magazine capacity repeating shotgun, as market hunters once used extended magazines on their Model 11s, before Federal limits on magazine capacity for migratory birds came along. In later years the term was applied to less expensive versions of several of Remington's flagship models.
hth,
lpl