...In a 16" bolt action, this cartridge would be a winner especially when suppressed. Not what I'd call 'amazing accuracy' but keep in mind, it's a 250 yard hunting round.
Finding a bolt action in 6.8 SPC has been difficult, to say the least. I think Remington produced a few, but on the rare ocassions when one of those turns up on GunBroker, they've been getting bid up over $1000 (which might possibly indicate some unsupplied demand). I've seen a few custom rifles, primarily based on Savage receivers, but even those go for very high prices.
Given the above, I think a run of RARs in 6.8 SPC would sell like hotcakes! I would prefer one with an AR15 magwell, but I would even buy one with a Ruger Mini magwell (if Ruger has a warehouse full of 6.8 Mini-14 mags they need to get rid of). In theory, Ruger could even go with a new mag well, designed to use LWRC Six8 mags (that won't fit a standard AR15 lower, but allow for seating bullets out, to a longer COAL).
For me at least, just being able to buy an American Ranch rifle with an AR magwell in 400 Legend is a possible (but more expensive) fallback option; I'm guessing it would likely be pretty simple to rebarrel one to 6.8 SPC.
As always IMHO, FWIW, YMMV, etc., etc.
