Thanks Hazcat - I'll take a look tonight. I have taken the tube spring out, and all looked fine (to me). It's like the loading gate is too stiff - some times when I push a round into the tube, there is so much resistance that it scratches the outside of the brass cartridges. Really, I'm concerned that it will damage the bluing on the loading gate in a very short time.
I watched a video of a kid loading his Marlin 1894 in .357 Mag., and he just popped them right in the tube with only his thumb. The kid couldn't have been more than 10 yrs. old. Either I'm an idiot, or something "ain't quite right...".
Thanks again - I'll check for debris tonight. The gun has been a safe queen since my step-dad bought it new, and he fired less than a dozen rounds through it. My guess - he thought it was too hard to load, and just put it back in the safe after cleaning it. OR, he just bought it on a whim to add to his collection, and the lube has dissipated from the hinge of the loading gate, and I need to squirt some CLP or something in there...