the ones where the muzzle brakes extend past the underlever a few inches? MK1's? The only 97's I've ever shot have been new models. Hmm, I can't remember if I ever tried a 77.
I'm wondering if the they are "better" than current production guns, in terms of tolerances and overall quality.
Back when I started working on spring rifles that was the new model. I always thought the HW77 long barrels shot better than any of the K models but most shooters found them muzzle heavy. Before the 97 was introduced, custom shops were into chopping them back and adding a muzzle brake. They did get less muzzle heavy but on a good many became violent when they were oversprung with the shorter barrel. On some with suspect barrels they also became less accurate due to loosing the choke.
Out of the box from the factory there isn't much difference in shot cycle between the older 97 and the newer ones. The longer barrel 97's that you refer to earlier on had 25mm ID compression tubes and toward the end had the 26mm that we have today. One is not better than the other and they have the same random issues that pop up with use.