With either a pump or semi auto that's barrel will remove can be changed to whatever you want it to be and of course is available...
2¾" chambered, 20" rifles sights for turkey, deer fine...28" for upland birds, excellent, 30" for clays, great...Then decide whether fixed choke barrels (much cheaper) or choke tubes and of course what degree of constriction (
see chart below)...
You can also get, if offered, a 3" or 3½" chambered barrel for it for turkey, geese, HD, whatever--all it is a longer opening for the shell to expand into and that is found on the barrel not the action...I've done it with Winchesters, Brownings, Remingtons and all have worked fine but with this proviso, 2¾" light target loads may not cycle/eject properly from the larger barrels...
You can of course buy them with the gun or from after market dealers either made by the original gun's maker or after market manufactures, like
Hasting's Barrels...Used/new barrels are available from
Corson's Barrels or from
The Barrel Exchange and of course places like Brownell's, Midway, Natchez, Cabela's etc...
I've dealt with both and recommend them...They will sell you extra barrels for just about any, non bespoke, shotgun made including SxS and O/U models if they have them available...I also bought a couple of Hasting barrels and they are just superb...
Now you have to decide upon semi auto (my preference) or pump and then maker...Remington, Benelli, Browning, Winchester, Beretta, Franchi, FN, Weatherby etc. for semis and pumps, Ithaca and then there's the rattletrap Mossberg which I'd never buy even if they do have a tang mounted safety!
Posted this on another thread...
FYI
Choke.....% in 30" circle at 40 yds
Cylinder.....40
Skeet........45
Skeet 1.....(46.5)
Skeet 2.....(48.5)
Imp Cyl......50
Light Mod...55
Modified.....60
Imp Mod.....65
Light Full....68
Full...........70
Extra Full ...75
Super Full...80