I'll just add to this, is that I have a plain London "Field" 12 bore with hammers and damascus barrels. It also has 2 1/2" chambers which are no problem for me.(I had initially typed NP, but no, not nitro proofed) Even with it's cylinder bores, it shoots very well. I missed one bird in 20.

Love it - so "lively". Hope yours is as well.