They may have already been lengthened, post market. I shoot small quantities oh the heavy field load out of my old 16s (1 1/8 oz shot at 1185 fps). iIt kicks quite a bit less than the faster load (express, Super X, etc) and works very well. N.I.Ds are pretty stout and you should be able to get by with just lengthening the forcing cones. I'd get the barrels and chambers checked by a good barrel man and go from there. I would be concerned with what heavy recoil can do to old wood than any actual damage to the barrels.
Last edited by Alder adder; 01/15/18 12:11 AM.
