What is Special about the "Special Purpose" that Remington makes in the 870?
It's because they are usually guns meant for specific types of hunting. Example: short barreled turkey models, rifled barrel deer models, or matte/camo finished waterfowl models. As opposed to general purpose types of guns.
The SP models are a slightly better quality gun than the express models. I know the bore in the the SP models are better quality and if your talking of the SP modes from the 90's then Remington built a better gun then also.
I have to agree for the most part, quality was better at Remington in the 90's. Having said that, I do like the VersaMax
I have a 870 sp from 1987, it has a parkerized finish, better than the matte finish that is used on the express models, the wood is dark stained walnut, and it is better looking than the cheap wood used on the express models. In my opinion it the best 870 pump ever made, except for my vintage wingmaster that was made in the late 50's, and it's as slick snot on glass! If I ever see another special purpose 870 for sale locally, I will buy it in a heartbeat!