I would consider this choice of cartrige for Moose and Elk inappropriate even for hunting at normal ranges say under 400 yards. It is not that it won't kill one. That is not the point. You can kill a Moose with a .22 rim fire but that does not make it a good idea. The point is that with a less than ideal hit or a hit in bone the smaller calibers are less likely to make a clean kill. Now you start talking about long range hunting you need to look at the terminal performace of the bullet at 800 or 1000 yards. The light bullets do not have much left at that range. Look at the math and you can show it to yourself. Throw in the fact that your going to spend a lot of money to build a custom rifle
for a specific purpose it does not make sense to choose such a light caliber for your stated purpose. If you were limiting your self to Antelope, Deer, and other smaller game then I would say that your choice is fine.
The minimum bullet weight I would recommend is a 180 grain but the heavier the better. Any of the 7MM, 30 caliber or larger calibers are the best choices.
My 2 cents worth,
Good Luck and have fun.