Currently I only reload for my .308, but would reload for either of those for the AR15 if I could only decide on one! Lol.
That would actually be ideal, but an AR10 is out of reach for me right now...If you are already set up for .308, why not get an AR chambered in .308? That way you can pretty much hunt any big game, and you don't have to worry about buying any new reloading supplies.
It's a trade off. As bore increases so does expansion ratio allowing you to use greater quantities of faster more energetic propellants. IE the velocity per unit of bullet mass increases.A 120g pill and powder in a 25wssm fills the case very well. A 30wssm would mean lower weight for cal bullets. You gain nothing but highly compressed loads.
I don't know why you think a 150g bullet is out of the question?Krochus, try putting a 150g pill in a wssm that fits in a AR15 mag. with powder... You will run out of room. The shoulder is hard to push back in a wssm. Compressed loads will make things more challenging. No free lunch.