Get ahold of Numrich Arms /Gun Parts Co. (not sure which name they are going by currently). Then have a long history of buying broken guns for parts.
Again, not exactly sure what the deal is, today (so call them) but in the past it was a simple transaction. You sent them the gun, they send you a check. If you weren't happy with the amount, you sent them their check back and they sent you back your broken gun, end of deal. GO find another buyer.....
NO, you won't get much, but considering the parts company has to inspect the gun, disassemble it to parts, INSPECT the parts,to determine which ones are resalable, sort the parts, then stock them, and they are going to sit, and take up warehouse space until someone buys them, and there's no telling how long that may be, years, or even decades, they simply won't give you top dollar.
Another option is DONATE them to a GUNSMITH SCHOOL. (it might even be possible for you to work a deal where if the students can fix them you get them back. I'd see if that were possible...)
If you strip them and sell them for parts yourself (online or wherever) you will probably get a higher $ return, but you will also have to invest your time, possibly more of it than what you will get in return value from selling the parts yourself.
OR, as mentioned, remove parts to render them incapable of being fired, and use them for decoration.
OR take some of our tax money back by turning them in for CASH at the next "gun buy back" program some idiot convinces our govt to spend money on. I'd go for cash, not interested in any "gift card" for a gun, even a broken one, but, that's just me.
Mossberg shotguns/parts are pretty common, Winchester 100s are NOT. The Winchester parts WILL be worth more than what you will get from any buyback program, I'm certain of that. Just go price the parts online, you'll see.