Everyone talks about the Mauser action because they are strong, reliable, plentyfull and can be inexpensive. I have a 338-06 which I built on a Interarms Mauser action. Barrel, action, stock, replacement trigger and gunsmithing costs add up quickly. For me, picking a caliber was the most fun. I just can't see the reason for doing a custom hunting rifle in 30-06 or any other common caliber. If you reload the choices are almost endless. If not then pick something less common but still available and useful, maybe a 25-06, 257 Roberts or 7mm Mauser. Remember to have fun and enjoy your project. Oh, I'm starting another rifle as soon as I find an action.