I didnt test it with the 6.5 Grendel other than attaching it to a few of my different AR-15s. Honestly I think there is plenty of room for the brass to be ejected into the funnel shaped mag well adapter. You could leave the spent brass box off and the brass would drop straight down onto the ground.
For the price this brass catcher is worth considering. For hunters, a smaller spent brass box with room for few brass cases might be desirable. For hog or varmint hunters shooting off shooting stick or tripods this might be a handy accessory.
I also attached the Brass Goat to AR-15s with different hand guards. I tested it with Keymod and two different M-Lok hand guards with no issues.
For the price this brass catcher is worth considering. For hunters, a smaller spent brass box with room for few brass cases might be desirable. For hog or varmint hunters shooting off shooting stick or tripods this might be a handy accessory.
I also attached the Brass Goat to AR-15s with different hand guards. I tested it with Keymod and two different M-Lok hand guards with no issues.