Riverside Arms/ Stevens 311? variant

[NDArmyGuyret]

I have a Stevens 311 variant side by side shotgun on the bench that has cocking problems and the underside of the barrel has the cocking plunger and extractor along with a part not shown in diagrams that slides back and forth. Diagrams show a spring also (missing). Anyone have an idea on the dimensions of the spring? I would elaborate more if I could find a model number, but just guessing it's a variant of the Stevens 311....Or point me to a schematic somewhere out there....Thanks.

 

[beag_nut]

Have you looked here:
https://www.gunpartscorp.com/gun-manufacturer/savstevspgfld/shotguns-sav/311-series/311
Numrich/gunpartscorp should be known by just about anyone familiar with firearms, like Brownells. There are several schematics about the 311 on the website.

 

[NDArmyGuyret]

Update:
did some more digging and found that it is indeed a Stevens model 315. Have a part listing but no schematic.

 

[gobsauce]

Update:
did some more digging and found that it is indeed a Stevens model 315. Have a part listing but no schematic.

That link that @beag_nut has the schematic. It's $1.50 + tax.