A couple of things to look for are residue under the ejector "star", and primers backing out from light loads.
You said you were shooting PMC factory loads, which should shoot fine in your handgun, but sometimes, even with factory loads, they will bind. When the firing pin detonates the primer, the primer backs out of the primer pocket. When the primer ignites the powder, the expanding gases then produce pressure, which pushes the bullet down the barrel, and at the same time, drives the case back onto the primer. If there isn't enough pressure, the primer is backed out and will bind a cylinder.
In the case of the extractor star, if there is any residue under it, that will reduce the clearance between the cylinder and the backplate. If this were the case, I would think the same condition would exist with both types of loads, but sometimes they do differ, so it's something to check.
Just a couple of thoughts.
Hope this helps.
Fred