My rifle shoots better with fireformed cases and cases that have been oncefired then body-sized.Can I shoot the new cases in another rifle of the same caliber and then body-size.I don't want to shoot 20 or so magnum rds down the barrel of my rifle to get cases to size.I would rather shoot them in a cheaper rifle that I have.Will this give me the same effect.

You will have to try this to find out. If the chambers were of very similar dimensions, it should work.

When you say "body-sized" I presume you mean the more commonly used term full length sized. Usually, neck sizing only is used to improve accuracy in a gun. If the chambers are similar ammunition neck sized for one gun could be used in another but problems could be encountered in guns with less caming force such as lever actions, pumps and semiautos with this approach.

In custom benchrest guns when the chamber is cut with the same reamer, you can fireform in the one gun, then use the formed brass in the other gun after (FLRS)full lenght resizing the brass in custom dies.The head spaceing has to be exactly the same. In a factory hunting gun the general rule is use only brass fired in that gun. No brass from a different gun. Tho many do it with no problems after FLRS.Its not a good idea to do it using neck sized only brass, but that sometimes works. If you try to force a round into the chamber thinking the bolt will size your brass for you, you will be making a trip to the gunsmith to remove a stuck shell from your gun. It wont go in and you can't get it out. I have seen it done. Remember, full length resizing does not fully size the brass all the way to the head/belt.

One thing you might try to is attempt to carefully (not too much pressure) chamber a fired and UN sized round from the cheaper rifle to see how the chambers compare. It could have a smaller tighter chamber to begin with!

Thanks!