Try e-gunparts.com for parts and Proofhouse.com has a cross reference chart that may help.
with a hacksaw
I have a 16 gauge double barrel for sale.
YES
yes
12 gauge double barrel shotgun
1000 bucks. That is how much mine is.
Not listed in any reference I have seen.
Generally it is stamped on the side or top of the barrel near the receiver.
It is a Stevens 311
A shotgun barrel with a cylinder bore choke.
Yes, it's a bolt-action 410 gauge shotgun.
yes a rifled shotgun barrel or smooth shotgun barrel