First-time moose hunter, and long-time whitetail hunter.  I've been told the shots will likely be under 300 yards, and I'm decently accurate at that range.  Working with different 130 -143 factory loads designed for deep penetration.

It's the only center-fire bolt gun I own and I'm not very interested in buying another.  If I wait for a standing broad-side shot I think I'm OK.  

What do you think?

Put it through both lungs then yes.

Shot placement gonna be key. Im willing to bet most will say it’s not enough if you make a mistake and don’t hit the heart/lungs dead on.

I totally agreed.

I'm decently accurate at that range. What does this mean? It sure doesn't inspire confidence in you making a longish shot in field conditions. Go shoot 3 shots from a  cold bore at 300 yards and post the group. If it's bigger then 6-8 inches from a field position, not a concrete bench at the range.   that's not a  reliable shot for you if over that size.

I would have no issues using a 6.5 creed at the ranges you listed. If you try and do tricky stuff like anchor the animal with an offside shoulder hit to anchor in place, the 6.5 creed probably ain't got enough ass behind it to do it, say like a 300 win mag.

It would be better to use something in the 30s, but I don't know anyone that's shot one in Idaho outside of 100-150yrd. Also a co-worker used a 30-30.

Regardless of what you use, plan to keep firing until the moose goes down.

Thanks, Guys.  Good responses all.

To clarify, I'm good in the field.  I'd say 2 -2.5 MOA.  All the hunting I've done was with 30 cals, but I've only got the 6.5 now.  

I've reloaded for 20ish years and it looks like a Hornady 143 ELD-X is packing 2000ish foot-pounds at 300 yards.  My common sense says this should work.  Several posters seem to agree a 6.5 is enough.

New gun, new caliber, new animal, but maybe I'm overthinking a little bit.

Why chance it with the 6.5 Creedmoor? Sometimes moose will be on a far hillside at distances of 500 meters other times less than 100 meters.