I have an old Ithaca SKB 500 20 Gauge O/U for the field and some 5-stand shooting. I have a friend who is an experienced gunsmith and restorer of antique guns, especially shotguns. He has my 20 for some minor stock repairs. He asked me if I want him to ream out the forcing cones while he has the gun. Is there any reason I shouldn't do that (assuming it's not chrome-lined, which I think not)? The gun has 3" chambers, and I might use 3" shells for pheasant, though I can't think of much else I'd use them for. The chokes are fixed IC/M. Does lengthening the forcing cones weaken the barrel for 3" or heavier 2 3/4" shells? Thanks to anyone who knows!