as long as your barrel is threaded 5/8x24 it will work
Yes this works great with 6.5 Creedmoor. I have this mounted on my 6.5 Ruger Precision.
Yes. The Midwest Industries 30 Caliber Muzzle Brake is compatible with 300 Win Mag which has a bullet diameter of 0.308".
Yes. The bore of your .300WM is .308" the same as a .308 WIN. It will work perfectly.
Yes........
The Midwest Industries 30 Caliber Muzzle Brake will use any .308 or 30 cal crush washer. I will link the JE Machine Tech AR-10 .308/7.62 Crush Washer below:
https://www.opticsplanet.com/j-e-machine-tech-ar-10-308-7-62-crush-washer.html
That information is not provided by Midwest Industries. I believe it to be right around 3 inches long, but to get an exact measurement you will need to reach out to Midwest Industries directly here:
https://www.midwestindustriesinc.com/Articles.asp?ID=259
There are plenty of options as the 6.5 Grendel has a .264" diameter projectile. This muzzle brake specifically is meant to accommodate .30 calibers which means it should also accommodate the smaller diameter of .264.
Yes, it comes with a crush washer.
That information is not provided by Midwest Industries. I believe it to be right around 3 inches long, but to get an exact measurement you will need to reach out to Midwest Industries directly here:
https://www.midwestindustriesinc.com/Articles.asp?ID=259