Standard throat? Who does that in a custom rifle??
I shoot 225 eldm out of both...the only difference is a slightly better ES out of the prc....
Bench
Custom rifles don't drive firearms and ammo sales. Even rifles like Cooper, Christensen, etc... that are a more "factory" option than a full blown custom or semi-custom build are the minority compared to things like Rugers, Tikkas, Brownings, Remingtons, etc...
Dog Hornady all you like, but the SAAMI spec chamber dimensions on the Creedmoors and PRC's allow for better accuracy out of FACTORY rifles and ammunition than what you can get out of many of the older generation factory/SAAMI offerings. The 300 PRC allows for heavier, lower drag bullets, and better accuracy potential out of a factory rifle than the 300WM.
For every guy here that posts a custom build in .300 Norma or a .300 wm with a custom match reamer, there's probably a hundred or more guys out there buying factory rifles that shoot 1.5-2 MOA. Well if changing to a .300 PRC factory rifle and shooting Hornady precision hunter makes that a sub-MOA combo... Might not die off like you think.
Also, to answer your question; I use SAAMI spec reamers in all of my PRC and Creedmoor rifles. No reason to dick with it.
There's also the military contracts... Which may not last forever, but the same principles apply here, that the original standard offering in the PRC is going to shoot/function better than the .300wm.
My personal opinion is that they probably won't, but belted magnums should go away. "We're better than that now"