I got a prime chuck For the same price as a choice cut. I put mine in at 10:00 and it was done at 1:00 cooking at 250. I foiled at165. Does prime take that much less time? Oh yeah, mine was 2.6 pounds.
I have heard that, because of the Marbling, but from me it's only Hearsay.
I never bought anything Prime, because I never saw a Good price on anything Prime.
Bear