Put an oiled, fired case in the chamber and let the extractor hook snap closed over it. Then move the slide back by hand and see if you feel added resistance to its travel somewhere around the point where the hammer passes half-cock but before the case clears the chamber? Also put an empty case in the magazine while you do this in case of rubbing there. If you can't distinguish an increased resistance from the hammer cocking effort, cock the hammer manually and try feeling for resistance again. Try the whole exercise without the recoil spring in place to see if you feel anything you can't account for.
Well that's an interesting test.
1) Hammer back, no recoil spring in the gun, no shell in the chamber. The slide rolls back smooth with barely any effort, like it's on roller bearings. Slight resistance when it touches the cocked hammer and pushes on the hammer spring, but not a lot.
2) Hammer back, no recoil spring in the gun, spent shell in the chamber with the extractor hooked over the rim. The slide goes back almost 1/8" then still locked, get's very hard to pull back. If I put a lot of force into it, maybe 10 lbs, the barrel unlocks and the slide goes back ejecting the shell.
So it's the barrel link then?