[IronJack]

What the heck is a “lifter?” Is that a legitimate term or just more profound ignorance on the part of the author?

[Paladin2]

Part to go from tube mag to chamber, I assume.

[thackney]

[KrisKrinkle]

The rifle in question has a tubular magazine located under the barrel, as do many other lever action, slide action and semiautomatic firearms. Partially working the action allows a spring in the tubular magazine to push a cartridge back onto the lifter. Continuing to work the action allows the lifter to lift the cartridge up in line with the barrel so it can be pushed into the chamber.

So far as I know, it's a legitimate term, although there may be others.