Did some hunting. West Point sold arms made by various manufacturers (Marlin, Savage, Stevens). I think you have a model that would be a Savage Model 65. Numrich has a magazine.

https://www.gunpartscorp.com/gun-man...les-sav/65-sav

The schematic also has part 24 listed as a "Takedown Stud". That cone/cylinder in front of the trigger group. Back that out and try again.

As far as disassembly: Here are instructions from the AR-15 site. It's not "simple."

https://www.ar15.com/forums/general/-/5-1133092/?page=1