WB
I have experiented with several rounds like that.
Friday, December 06, 2019, 14:39

Many of the GNR rounds can fireform perfectly like that. .30-30/.30 GNR, 7x30/7 GNR etc. You cannot fireform .256 Falcon from loaded .25-35 Win. It splits! As do many reloaded versions of the aforementioned numbers. Once fired the brass can become work hardened, as it can simply with age. Expanding it too much too fast results in splits.

Even firing .22 Hornet to K-hornets sometimes results in neck splits. I have even fired loaded 7.62x39 in an ancient .401 Winchester making rimless brass. It worked too.

Answer; maybe. New ammo may fireform from .204 to .257 Raptor just fine. The TC holds the case by the rim-notch and will fire it for sure. But that is a pretty big jump from .204 to .257 and might split. Sometimes we even anneal brass necks to expand in a step or three up to that .257 just to be sure. Like .22/.243/257 It's better safe than sorry. It's part of the fun too. You can't get a 100% definitive answer but you have to make your own choices given the information.