Buddy, it is essentially a field grade Remington 1100 at it's core. The 12ga Sportsman is closer to the 1100. It was made a few years prior to the intro of the 11-87. I know that it has a barrel extension same as the 1100 and many of the other parts are common. Cheers and stay safe!

the sportsman 12 was made in model the model 48, model 58. model 870 and the Model 1100 so without knowing which it is it will be impossible to tell you what will fit. I agree with Michael get a pawn shop 1100 or 870 to use as the basis of your tactical shotgun and keep the memories intact in the gun from Dad. 30 years ago my stepmother would not even let me buy my dads Remington 58 when he died and it is still a sore spot with me (she sold it to someone else )

Buddy, You can do whatever you want, but I'm not giving you any tips. Keep the heirloom hand down from Pops just the way he passed it on to you. Don't bubba up your Dads shotgun.