RWTF: They sure did. Starting in early 1941 (just before the war), Remington made some 12-bore M31 aluminum receivers. WWII evidently stopped all non-military production until about 1946-7 when Remington resumed M31 12-gauge aluminum receiver production. The model was called the 31L for "lightweight". By 1948 (as I remember it) they began sub-gauge production, starting with 20s and then later that year, 16s. I now own two, a 20 and a 16. Both weigh about 5 1/2 pounds empty. They weren't designed for competition use or any high-volume shooting, but... of-course many were used exactly that way, leading to cracked receivers and dependability issues (hardened steel parts inside an aluminum receiver will inevitably cause wear issues). Remington clearly couldn't afford a reputation problem so they ended M31L production around 1952, which is a shame because they work just fine for hunting use.
My 20 with a Colorado Bolete mushroom. The anodized-black receiver is a dead giveaway that it's a lightweight gun.
They feel strange when you first pick one up (because you're expecting 8 plus pounds, not 5 1/2) but the balance is still quite good and, of course, they carry wonderfully. My exclusively pump-gun shooting (then 70-year old) father-in-law was having problems carrying his almost 9-lb (loaded) 870 Express around all day back in 2010. I found the 16 bore M31L for him then and he proceeded to kill mounds of ruffed grouse with it for the last 10-years or so. He really loved it.
