My beater is one that has to be immune to the occasional incident in the high country after goats. A couple of tumbles off rocks has a few scars but I am not afraid to use it in these conditions. Not a big cartridge as this is not needed for these animals but the 6.5 Grendel Max is my own wildcat so I have a soft spot for it. A heavily modified Mark X mini mauser in a self made laminate stock.
I started out with a suppressor but its length was an issue so I made a muzzle weight to keep the balance the same as in this pic but found that a slight muzzle lightness was no impediment for off hand shooting so now it has neither and the handy 21 3/4 in length makes it a nice 6 1/2 lb to carry up to the steep places.
Can your AR magazine take the 2 4.5 length of the Grendel - Max cartridge. Some have tried and not got much more than 2.3something. It really is optomised in the bolt rifler with either a modified micro action like the mini mauser or the standard short actions. Being able to use the standard Grendel dies was one of the things I wanted to stay with for the cost effectiveness of a simple re-chambering and spacers for the dies.