As Gary did, I thought long and hard about both.
The scales, for me, tipped slightly towards the 6.8 SPC.
and that is what I purchased. Mine is a 16" RRA upper with
a free float tube. I added a quad rail gas block, and
a tactical latch, to the upper, and pinned it to a Superior
Arms, lower, with lots of goodies on it. Regrettably, I
don't have pictures. I have not gotten a shot at a coyote
with it, but a couple of other vermin have taken hits
from my 110 gr. VMax loads. Pretty violent stuff.
I am sure it is not fur friendly. I am extremely happy
with this choice. So happy in fact, I am going to build
a 6mm WOA(6.8 SPC necked down to 6mm with a slight shoulder
change).
So why did I choose the 6.8 SPC over the Grendel?
First, the death grip on the case design, and the
premium price for the Grendel, because of it, stuck
in my craw. Second, the Grendel left very little on
the floor, in initial development. On the other hand,
the 6.8 initial development, by Remington, was poorly
worked, and left much potential left in development, when
they seemingly abandoned it. Second and third efforts,
have gotten much more velocity, out of round. Add some
improvements in bullets, better suited to the case
capacity, and efficiency, and I saw little difference.
Many comparisons one finds are with the Grendel vs. 1st
generation 6.8 SPC chambers, twist rates, and early bullet
choices. Comparisons with the Grendel vs. the 6.8 SPC,
in 1:11-1:12 twist barrels, DMR chambers, and new bullet
offerings, would show little to no advantages between
the two case designs, at ranges out to 400 yards. After
that, the Grendel get the advantage not by the case design,
but by better long range bullet offerings, in 6.5mm. The
6.8 gets a slight advantage in round count in magazines,
and in brass supply, and cost. More brass sources for
the Grendel may be in the future, driving prices down,
but the 6.8 has Remington making brass, which is a
far distant second to Silver State Armory brass. SSA
brass availability has never been an issue, and SSA sells
it direct, at a fair price, along with good deals on loaded
ammo.
Good Luck with the decision. Unless one is a Kool-Aid
drinker, in either cult followings, the choice will
probably boil down to factors other than real world
ballistics.
Squeeze