[Brian Pfleuger]

Gravity still applies inside a firearms chamber so unless there's a reason that it is forced not to, a cartridge first of all sits in the bottom of the chamber.

In addition, any pressure from an ejector will slightly cant the cartridge if there is any space to move it.

A "properly headspaced" cartridge will have 1 or at most 2 thousandths of an inch of space (length) in a bolt gun or 3 thousandths or so in a semi.

If the dies are made for the gun, the entire body will have 1 thou or so space around the sides.

If the dies are generic (which almost all are unless they're custom), you'll have whatever space is the difference. No way to know. The die could be SAAMI minimum and the chamber could be SAAMI max or anywhere in between.

In any case, gravity applies, so unless the cartridge is (improperly, BTW) "crush fit" in the chamber, it will sit on the bottom and be pressed slightly to the side by the ejector.