I have one of the original 28" LW barrels that came out of Germany. I have a little under 1000 rounds through it, all done load testing.  I won't post all the details here, but the short line is that the results have been varied.  I bought it to make a long range varmint upper (500-1000+ yards). The cartridge is capable, but this barrel, at least, is finicky about seating length, powder/primer combinations, etc.  I have yet to find a magazine length load that will shoot much better than MOA. Seating out to the lands gets me pretty good groups (only out to 300 so far), but the best of them can open up substantially with a powder change of 0.2 gr of powder or a 0.010" change in seating depth.

Another 28" barrel is on the way, with a modified throat. I'm hoping this will be a better fit for me as I want to shoot magazine length ammo for dog shooting.  I have no experience with the 24" or the 19.2", but have heard that they are not throated for long-seating of the VLD-type projectiles. and are more consistent with mag-length loads.

As to mags, Walker is correct. I was having many feed and lock-back problems with mine. I got some machinable followers from Magpul and fitted them. (I'm the one who told Arne about using them to correct the problems with the original followers.) Before I had feeding problems that were significant. I could consistently shoot dual groups, about 2 inches apart at 100 yards. One group was from the left stack, the other from the right stack.  120 gr SMK's were just under an inch, just got two of them.

Zak,  I agree that a 6.5-284 in a bolt gun is tough to beat. But many, maybe most, will blow out the throat in 6-800 rounds.  In a week's dog shooting we often shoot 10k rounds or more.  (Not long range, obviously, but I would need a switchbarrel and a big sack of tubes to use one for this.) Plus, 30 gr of powder per, versus twice that for the bigcase .264 rounds bumps the cost (and recoil) up a good bit too. Lapua makes a 144 gr FMJ in 6.5 that shoots sub-MOA nearly forever. (Stays supersonic beyond 1200 yards.)  There is also some evidence that Sako may build a #1 action sporter in 6.5G. This would make a great lightweight rifle for mulies, antelope, etc. when you may need to make a long shot but not like humping a heavier rifle.  A 5-5.5# Grendel would not have punishing recoil, others in this caliber might if set up in an ultralight.

Al in all, I like the Grendel. ( I just got another 2k pieces of brass). I wish it were easier to load for, consistency-wise, but I like having the ability to shoot 1000 yards with a 600+ BC bullet that has minimal recoil.