When it hangs up the rim of the case is not fully engaged in the extractor correct? The heavy wide flat bullets have less room for error when it comes to feeding. Smaller round nose or jacketed have a fast taper to the nose and can be off center to the chamber a bit and still feed. Not so with the wide flat nose bullets. All of your room for error is lost by that big wide nose You say the extractor spring looks like my second pic. Did you pinch the spring where it attaches to the extractor that was the clincher for me. The bigger bullets need the brass to engage the rim quicker than the round or tapered bullets. While the rim is trying to engage it is pushing on the extractor and compressing the spring and opening the extractor to accept the rim. The weaker the spring the easier the rim will engage. If that fails polish the extractor between the claw and the nub below. You might have to make that gap just a bit larger. Do not loose the 90% angle of the claw while polishing. When I say polishing you may have to remove a tiny bit of material then polish smooth. Load up some dummies and work them through the action. I asume you have a good crimp on your bullets also. Remember when the 44 mag was developed it was based on a 250gr bullet I believe of the Kieth design for a pistol. Thats probably what a Marlin was meant to feed not what you or I are trying to stuff down them. Be patient you will get it. Good luck.