We've been down this road before. Building a rifle for 1 match. Yeah, there are other Area or rifle only matches that use USPSA rules (and some that say they're using USPSA rules), but the reality is that the ONLY major 3-gun match that major PF is acknowledged is Nationals. I'd wager that the $10k bonus money from AAC factored into Daniel decision to use it at Nat's.
The only thing going for 300AAC/Blackout/Whisper is that the brass is easy to manufacture if you have a Dillon trimmer and the trim die from M4C (or whoever). They feed in Magpuls with some tweaking, so you can load 48 with Nordic extensions. However...making power factor is a different story. It's been done, as evidenced by Daniel, but I'll wager there was some work done to that barrel to make it get there. I wasn't there, but I would wager it barely made major. On top of all of that, unless something new has come out, from everything I've seen trajectory wise, it sucks. After about 175 it drops out of the sky faster than just about anything.
We had one local guy use it at the BARC in Heavy Optics, but the MD dropped the power factor down for him and one of the match sponsors using an AK. So...surprise, surprise that they took 1st and 2nd with 48 and 30 round mags respectively and the 308 shooters, shooting 320 pf and 20 round mags trailed behind.
I'm considering rebarreling an old rifle to it, just for plinkin', but that's WAAAAAY down on the priority list.
Rich