That's a great read, and very on-point with regard to communication and trusting your spotter. That lesson concreted itself at the Spring Shoot when a miss looked different from my perspective, yet trusting the spotters call got me on target in a jiffy, rather than adjusting by my data.
There's no wrong choice there, I'd personally base it on ammo availability right now. I think you'll have less trouble finding good 300 Win Mag ammo than you will good 6.5 Creedmoor, but if you reload that's all a moot point.
I have the TAC A1 in 6.5 Creedmoor. An incredibly accurate and smooth rifle. Beautifully engineered and well executed in it's design, it's a masterpiece of form and function. I highly recommend it.
You're absolutely right, ripping up squirrels with a saw would be unethical. That's exactly what the minigun was for, handling any over-aggressive tree rats that might take exception to the modification of their natural habitat.
That's a good idea, more useful working load, and can have a door gunner man the Dillon minigun, just in case some squirrels get out of hand, or something....
I don't know that your issue has a single cause, but I DO know that you've found and can correct a significant issue. When you have the right length gas tube, it'll end at or very near to the center of that cutout.
Quantify for me where it should be going and why. Bear in mind, this is not the standard AR platform, so I'm not interested in the old wives' tales from the standard AR side of things.... Where does the brass need to go, and more importantly, why?