Congrats on the new rifle the cooper excalibur I own is one sweet shooter ITS IN 6.5X284. I shoot a 270 win Weatherby mark v Accumark and it shoots 130's .5moa the 130 VLDH is emphatic with 100 pound whitetails. It is destructive though with exits in the baseball size range. They don't travel far though. The 150 partition is also an excellent choice not as destructive and just as emphatic.
I would think the 140's would be a good choice but cant get the 140 NAB to shoot from mine as well as 130's and 150's. Going to try the 140 SST when I can get around to it. But the performance of the 130 HIB has not been very good from my rifle.
Check out this article from terminal ballistics.
Good luck and shoot straight
You are an inspiration to me..the 270 winny is as good as it gets anywayHere is the reason I chose the .270 Win instead of a large caliber. Because I am paralyzed from the neck down I have to use a shooting rig on my wheelchair and cannot have a huge recoil. Here is a picture of what it looks like. I was setting up for my bear hunt last September.