Made by the same firm that made the Civil War Spencer Repeating carbine.
The Spencer shotgun was the first successful American slide action shotgun.
They were made from 1882 - 1889 by Spencer Arms Company of Windsor, Connecticut but due to financial problems sold their patents to Francis Bannerman & Sons - of New York City in about 1890.
It was built in both take-down and solid frame configuration - in different grades of quality - and went up to 10 gauge.
Bannerman would continue it's manufacture until 1907.
This should be a Savage 18-D.
That was a slide action shotgun, not a rifle, and was obsolete before 1920. No 'blueprints' are available. What are you needing to accomplish? sales@countrygunsmith.net
Collins books might have something on the company
Have you tried the Internet?
Need the maker of the shotgun
Google.
Go to Cheaperthandirt.com
Underneath the action just ahead of the trigger guard is the loading gate. The shells are pushed into the tube until the tube is loaded. Once 2 (two) shells are in the tube, press the slide release located just ahead of the trigger guard and to the rear of the loading area rearward and rack the slide rearward. This action will load one (1) shell into the barrel, allowing room for a 3rd and final shell to be loaded into the tube. To unload the shotgun, press the slide release rearward once again, and repeatedly rack the slide to the rear, ejecting the shells. Do this until the gun is unloaded.
That will depend on the make of the rifle and the age of your pump rifle.
I have a Marlin Firearms Co. 12 gage, bolt action shotgun.
The Stevens 311 is a double barrel shotgun.
1937-1965. Parts at www.e-gunparts.com.