RE: Antelope and 223???
Def check to see if its legal....if so, I'd say heavier bullets are better.....50-75gr....
talked to a guy in MT who loved using his .220 swift on antelope all the way out to 300-500yds.
course thats more powder/power....so I would assume the swift would shoot those heavier bullets faster and with more energy.
Either way you'd want a premium bullet, not a hollowpoint.....
.243-.270 is a better route to take I'd say.