Remove buttplate. Use a socket extension and rachet to unscrew the stock bolt (it's in that hole in the center of the butt)
hire it done.
To remove the buttstock of a Stevens 311 shotgun, first ensure the shotgun is unloaded and safe. Use a screwdriver to remove the screws located at the rear of the receiver that secure the buttstock in place. Once the screws are removed, gently pull the buttstock away from the receiver to detach it. Be cautious to avoid damaging any components during the process.
there is the Stevens side by side shotgun model 311
Try e-gunparts.com, Shotgun News, Gun List, do a web search on "shotgun stocks".
The Stevens 311 is a double barrel shotgun.
Try e-gunparts.com
100-300 USD
Numrich Arms has parts for the 311
You may be able to find the information you are looking for through this web site: http://www.huntingsociety.org/gunstocks.html
To take apart a Stevens Model 311 double barrel for stock replacement, first ensure the shotgun is unloaded and the safety is engaged. Remove the forend by pushing the release lever and sliding it off the barrel. Next, locate the stock screw at the rear of the receiver, unscrew it using an appropriate screwdriver, and then gently pull the stock away from the receiver to detach it. Be cautious to avoid damaging any internal components during this process.
100-300 USD
I think it is the same as a Stevens 311, made by Savage Arms, for marketing by Sears. A great, utility shotgun. If so, a stock for a Stevens 311 should fit it, but there are two types: one with a straight edge where the stock neck meets the receiver, and the other with a notched edge. Good luck.