Hi flatbow, yes, I'm saying once fired brass from any other gun will not fit even after full length resizing, unless you use a small base die.
You'll have no problems using brass 1st fired in your own chamber.
In a Contender, unless using light loads, you need to full length size your brass just enough so the action will lock easily, Hornady Manuals explained this for the 30 Herrett but it applies to any case with a shoulder being used in an action that does not have the camming power of a bolt-action. This can also be seen by "smoking" the case with a Bic lighter before resizing to "witness" the shoulder of the case being "bumped" back.