Going from memory, as usual, my early K-22's have the narrow rib and more noticeably tapered barrel. I have a 17-3?, with a somewhat wider rib and a straight tapered barrel but I also have a 17-5?, with a wider rib and no taper to the barrel, similar in appearance to a model 19. Subsequently, Smith went with the full underlug barrel, I had the opportunity to shoot a 617, with the full underlug, felt like a small child was hanging onto the barrel but I never had the opportunity to buy a 17 with the full underlug.