There's not a lot examples of the the Grendel out there. gr8santini has a new(?) one but hasn't posted up any accuracy results with it. I'm guessing if you've been watching the forum, your 2-3 reference is from what I posted in the 6.5 thread.
I'm a hobbyist (RIP EC), I've got way more guns than I need, so I don't devote all of my time to my M or L to figure out exactly what they like. From the factory and their shooters (keep in mind the source) it would seem the platform is capable of excellent accuracy. Hand loaders have had some great results as well. I've posted about my experiences on the forum several times. I'm just some dude that likes guns with no worthwhile formal training. Take it FWIW. My experience with accuracy has been spotty. I'd wager that any of my similarly equipped ARs are going to be more accurate than my XCRs. Most, if not all of my ARs are capable of sub MOA with the right ammo and if I do my part. I'd say my XCRs are 1-1.5. I've had some instances of hole in hole but when I've shot more than a few rounds the groups start to open up. My most consistent XCR is an 18" 5.56 that hovers right around 1 MOA, but it's consistent. I've had some other barrels shoot well for a few rounds but will throw 1 or 2 in a 5 round string. My experience with the accuracy and the deflated gun market have kept me from trying the M in 6.5. I don't want to gamble the money on a barrel that may just be OK.
I've been limited to 140yds max for all of my shooting. I'm hoping mid to late this year I'll be able to regularly get to 500yds but time/work will be the deciding factor for that. If I can get out further, I'll post up what I find.
RA is putting out a much more consistent product now. QC seems to be much better and the fit and finish on the rifles is way ahead of where they were when they started. I'd chalk up any issues with reliability to crappy mags (5.45 in general and older 762x39) and me messing with the gas system. I've only shot a bit of the 100gr wolf but it's been good so far. Using a mix of e-lander and ASC/cprod mags.
I love the platform, own several examples and will continue to do so.