I do not have any direct experience, but do have experience with getting a 6.5x55 CZ to feed...once it was converted to 9.3x62...

Watch the rounds as you feed them thru the action. Watch the RELEASE of the round from the mag and where that puts the case head vis-a-vis the extractor. I found that the shorter 6.5 round popped out of control of the action rails before it was under the control of the extractor. It never popped up under the extractor, rather...jumped head of it.

You comment on the Lott feeding more reliably than the shorter Win Mag got my attention.

If the case releases from the action rails prematurely, I don't think there is anything you can do except go to a longer case, meaning in this situation, the Lott.