Sorry Owen, I misunderstood your question. As far as being worth a purchase of an ARC when you already have a 6x45, I don’t see the need nor the gain. A 6x45 is probably a better choice for my intended purpose, that being shooting coyotes with lighter bullets. I think the Howa is a 1:7 1/2 twist, fast. I would be quite happy with an accurate bolt action 6x45, which to my knowledge is not available without doing a rebarrel. My 6x45 is an AR, a good one from Mike at Dtech.
Velocity of my specific 20" ARC is less than I was hoping for, putting it in the same velocity range of the 6x45. Brass for the ARC is expensive vs. the cost of .223 brass. Necking up a .223 is a simple process. As well, I load most of my bolt actions with Lee Collet neck sizing dies which have always given me very good accuracy. The ARC, however has an issue in that neck sizing alone doesn't allow it to chamber, thus the need for a body size die. I was not expecting that. According to AI, assuming it is correct, the Grendel / ARC brass by its design, needs to have the shoulder set back slightly, even for a bolt action.
I purchased the Howa Mini 6mm ARC for a couple of reasons. First, as you know, I like to mix things up a bit and as such like experimenting with various cartridges, bullets, rifles and platforms. It keeps my interest level up. Secondly, I wanted a bolt action platform, short heavy barrel that is more conducive to suppressor use, and a cartridge that would yield suitable velocity and accuracy as well as 6mm minimum bore size. After quite a bit of searching and reading, I settled on the 6mm ARC. I had originally thought of a .243, but also wanted a cartridge that would suppress well. The ARC uses considerably less powder than a .243.
So, having said all that, I really do like the 6mm ARC cartridge and the Howa Mini bolt action. The cartridge chambers well. The trigger is good from the factory and accuracy is generally 1/2" at my coyote shooting range of 80 yards, plus it is available in 20" heavy and threaded. If I had it to do over, I might would have kept looking for a different cartridge, simply because of the added work in reloading. Discounting that I have no issues with it. The velocity and accuracy are plenty good enough for my purpose, though I was hoping for a bit more.
I have a brand new, never fired Remington 700 SPS stainless in .223 that I purchased a few years ago for the express purpose of rebarreling to a 6x45. I haven't taken the step yet to do that since the rifle now is probably worth a premium as it is. I also have a camo stocked Stevens 200 .223 that I have considered rebarreling, and should be an easy barrel swap. Who knows, I may get a wild hair and acquire a 7mm08 !! lol.