As far as I know. Investarms doesn't make a 28" 1-60 twist.
The 1-48 twist is fine for PRB as long as you don't use huge powder loads. They really aren't needed with a PRB.
It should also shout conicals pretty good too. No too short though. That would be more for a slower twist barrel. Bullets like the maxi ball should do well, but you need to try them to see for sure.