If that’s a Tacstar side saddle, it’s a notorious piece of shit that will definitely squeeze the receiver if tightened too much. Not tightened enough and it falls apart. Then it starts scratching up your receiver.
Any aftermarket shell elevators in use?
I’d take the magazine tube apart and clean it well inside. Do not apply oil inside the magazine tube at all. I’d recommend making a polishing jig for the magazine tube. I put a 12 gauge cleaning rod in my drill gun, then wrap fine steel wool around a 12 gauge chamber brush. Then go to town up and down the inside of the magazine tube for 5 minutes. Clean out the residue and admire the mirror finished magazine tube. Note the difference in sound once you reinstall the spring and follower. The magazine spring won’t be fighting the resistance inside the magazine tube as much so that it can deliver more of the spring energy to loading shells onto the elevator. This is particularly important when it is the last round or two being loaded from the magazine. The polishing can be done on steel, titanium or even the Briley carbon fiber magazine tubes.