That’s crazy to do a 10lbs 300PRC for hunting. Don’t do it
A 308, 7mm08 and a well placed 6.5 will drop elk with proper shot placement and proper bullet.
A good 7mm bullet in the 150-180 range, shot at 2600-3000 FPS at the right place will kill anything on this continent. I mean a 243 will easily kill a mule dear.
If factory ammo is important to you get the 7 Rem Mag is probably easy choice but if you can find 280ai easily then for me it’s the best choice for all around cartridge in a long action, I’m recoil averse on hunting rifles, 280 AI performance loss vs as 7 REM mag is very little but you get less recoil, better inherent accuracy.
Personally I went with a 7SAW (similar to a 7mm-08 AI) but my hunting rifle is in a short action. Gets me 2725 out of 162s with a 22in barrel. Friend of mine likes his 7-6.5PRC, perfect for tikka length action but even out of that bigger case, not that much better performance than my SAW and uses 20 more gr of powder, is it really that worth it for an extra 100-150 FPS ? That’s for you to decide
7 PRC is great too but finding ammo will be harder initially. Took a while to get 6.5 PRC and it’s still kinda hard to get.