Been off the forum for a while. Came back and saw this thread and thought my input might be useful.
I have the Ark30 (mine's the screw-on type, the 1st generation of Ark30). I use it on .308, 6.5 Grendel, 6.5 Creedmoor, 5.56 and 300 Blackout. On about 50% of the rifles tried, it reduces the size of the groups. About 40% of the rifles, the group size is same as with no suppressor. About 10% of the rifles, the group size enlarges. No big deal on the enlarging of groups...I have a Quicksand to try on those rifles. If a rifle doesn't play well with one of my suppressors, it typically plays well with the other. FWIW, the Quicksand only improves group size on maybe 25% of the rifles. I am VERY happy with my Crux Ark30, especially in the accuracy and weight areas. It is not as quiet as the Quicksand, but then the Quicksand is 1 1/2" longer so more volume in it.
Service - So one day I find a crack in my Ark30. I did not abuse it! Matter of fact, I normally let it cool to ambient temp after each 5 shots, via a Caldwell barrel cooler and/or external fan on it and the bbl (I'm easy on most of my barrels), and the only <16" bbl it's used on is the Blackout. Contacted Crux Feb 17th. Shipped Ark30 to them a day or two later. Crux tells me one time they are waiting on material. Crux tells me another time an extra employee has been hired to help with the volume of work. Crux says some pieces of the metal stock they were sent suffered from hydrogen embrittlement (whatever that is), and that is what happened to mine. Repaired suppressor is shipped back to me Jul 1st. It's been running fine since then. Oh, Crux told me they upgraded it to their heavy duty specs (but for the life of me I can't see what the difference is, as it looked the same). I suppose if I could get it apart, I could compare it to friends' Ark30's bought the same year (they've never had any problem or cracking with theirs).