If different length shells suffer the same problem, then, more than likely, the mag spring is compressing.
Are the cartridges getting caught by the rim?
Check the shell latches, the long springy things that control cartridge feed.
There's two, right and left, with small hooked ends right at the end of the mag tube, inside the receiver.
One could be bent some and catching the cartridge rim.
Lock the doors, they're coming in the windows.