I haven't had even one example of even half of the American made pump shotguns, so I'm taking a big leap to make any judgement on which is, was, or will someday be best. To name a few I've never had a Win. 93, 97 or 1917, any Mossberg pump, Rem. 31 or 17, Marlin, High Standard, Savage, Stevens, H&R, or any US made Beretta or Benelli.
My favorite was an OLD Wingmaster. Tight enough to shoot well but loose enough to shoot all day in the mud. Fairly easy to fix and lots of aftermarket parts. I've heard knocks on the newer ones, but don't recall any complaints about mine and don't recall that it ever failed me. Theives got it.
The M37 (i.e., Rem. M17) was of course (partly) a John Browning design. That itself should give it a headstart on the others. I have an OLD M37 that's OK, but I'd rather have dual action bars and not have bottom ejection. It's the sloppiest action I've ever had on any gun and I can never tell when its loaded or not. I have a newer one with a 3" chamber and choke tubes that I got at a yard sale for $25. It seems to be about the same quality as the old one.
I never had a M31, but I'm told they were tough to take apart and since most parts were hand-fitted getting them repaired was a gunsmith job. Not something I think would want in a pump shotgun. Of course if no parts ever break fixing the gun isn't a problem.
Believe it or not I also like my Winchester M1300. I don't use it much anymore since I picked up my first Beretta SA. My favorite feature on the 1300 was the "pump assist" that helped open the bolt after it was fired. Unlike the 2 1200s I had the 1300 has never really failed me. Can't figure why because the parts are mostly interchangeable.
