I've never been prong horn hunting, but judging by their size I would say anything from .224 to .308 caliber would work well with 24s, 25s, and 26s, being about perfect.
However for me, the .270 Winchester would be my first choice simply because I love it.
My hunting bud and I have killed them with .270 (his), 6.5-284 and .240 Wby. All dead, mostly DRT. One was still breathing, moving his head (hit with .270) Guide finished him off with a .22 WMR Ruger revolver. All the rest were DOA when we got to them.
Easier to kill than to hit.
DF
