Assumptions made in answering:
1. Animal is in the clear.
2. Load is adequate (180gr or better).
3. Wind is minimal.
4. Visibility is good (nothing between you and said moose).
5. Broadside shot - I mean really - 9" kill zone is not so hard at that distance....
6. You're not standing (prone or supported shot).
Given those conditions, I would be 100% go on a kill shot at 400 yrds and less.
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Im not really advocating what exactly what the .308 can or can't do.
The assumtions you have stated, well, I figures they not need to be stated.
1. Animal is in the clear....well I don't shoot at animals that aren't, and at 400 yrds, I figure many others don't.
2. Load is adequate...again...
3. Wind is minimal,.. this is a different one. Knowing the limitations should address this.
4. Nothing between you and the moose...

I hate shooting when there are schoolbusses driving between me and the moose.. (seriously, this one?)
5. Broad shot, 9" ...knowing your limitations, and that yours aren't necessarily others.
6. You are not standing... (????) or eating pie
I'll add some...
7. You are not on your cell phone at the time...
8. The anaimal is the right ### for your tag
9. You see no other hunters near the moose.
10. It is not night time.