im sure it can be done
No, not yet
nowhere
Remington now imports the Baikal shotguns under their 'Spartan' brand. Barrels for the "Remington" Spartan SPR-453 are the same as your Baikal.
No it does not.
On the Baikal/Remington SPR 310 O/U, you simply push the trigger forward to select the top barrel, leave it alone to have the bottom barrel fire first.
18.4
It is possible
A barrel nut is an internally threaded screw with a slotted head.
All you must do is purchase an A5/X7 threaded flatline barrel and screw it in, becasue they have the same barrel threading. 98 threaded barrels will not work.
yes, both spyder threaded
You will probably have to contact a barrel maker.
Any autococker threaded barrel.