40-210 or so
No way to tell based on your description.
Probably Uberti. Look on the underside of the barrel for manufacturer's logo/markings. The "USMR" marking is historically accurate and appeared on original Walker revolvers. Stands for 'United States Mounted Rifles' which was the regiment of the designer. sales@countrygunsmith.net
25-75 USD
Once you have the forearm removed you need a special spanner wrench to remove the tube/nut below the barrel. The bolt handle pin is then drifted out of the bolt and then the bolt handle can be removed from the bolt body. The barrel will now come out the front end of the receiver.
If the action will handle the caliber and if someone makes one and if the barrel profile is the same, yes.
Finish? Barrel length? Grip material? Range 100-500.
10-100 usd
fat black bucks in a wine barrel room Barrel house king with feet unstable sagged and reeled and pounded on the table pounded on the table beat an empty barrel with the handle of a "BROOM"
go to gunbroker.com and you'll see all you can handle.
Most shot guns can handle deer slugs.
100-200 or so
Such an item would be a custom piece. None are manufactured in that configuration.