Negative. I think what you're experiencing is a condition where the inferior attributes of your choice are setting in, so you transfer those attributes to something that is competitive and superior with your choice in many ways, even to the point of depositing this internal struggle all over a thread where a guy is looking for advice on eradicating predators from his property in a region where distance and wind are significant considerations, referring to your post even as the "OP". The original post is about looking for a viable AR15 under $1500, later quantified by the need to deal with predators.
Regional Considerations
If we were out in the Great Lakes Region, or the South, shooting from blinds within dense deciduous forest where the distances were 200yds or less, an animal won't know the difference if they were hit from a 120gr 6.8 SST or a 123gr 6.5 SST.
Out in the Rockies, the terrain and landscape are totally different. Average hunting distances, especially on predators, is often 2-3x what it is out East. That means you need a cartridge that will buck the wind well. If you use a 200yd zero, the Grendel will keep you in Point-Blank Range longer than a 6.8 SPC-just the way it is because of wind-deflection.
Echo chamber Statements
The reality is that you parroted a familiar statement about the 6.8 SPC:
For hunting under 400 yards go 6.8 spc II.....if you are target shooting over 400 yrds and reload go 6.5 Grendel
I've seen this statement now for years by those who are loyal-to-a-fault, dedicated advocates of the 6.8, to the point where someone who doesn't have experience with these matters reads it online in an echo chamber, sees it repeated over and over again, then posts it as gospel truth, and expects to let it stand as sound, logical advice.
Then when called-out, simply accuse the person pointing out the numerous falsehoods of the statements as "skewing data", when that data shows a real comparison. You have to remember and try to process this: I was in the same boat when 5.56 AR15's were all that were available. I had every intention of owning a 6.8 as soon as I heard about it, until the Grendel became available. I used to believe the statements about 6.8 being better for hunting because my initial interest in the Grendel was only as a lightweight target/DM system.
After seeing that my .260 Remington smoked my .270 Winchester at distance, from a 300fps handicap at the muzzle, I then started wondering about the 6.5 Grendel and 6.8 comparison from a hunting standpoint, back when we were being told that there were way more hunting projectiles for the 6.8, supported with the following picture:
http://www.hunt101.com/data/500/68bullets34am.JPG
It seemed to be a well-intended, reasonable statement, based on photographic evidence even. Only problem was, it was totally false by a factor of being maybe 25% of the available projectiles for the Grendel, even if we include all the GS Custom and discontinued Elite solids for the 6.8 SPC.
I'm still not sure how many projectiles are available for the 6.5mm, because there are so many to track down. There are well over 100. Here is an old photo with less than half of the 6.5mm bullets, before the 123gr SST even:
Magazines
For everyone I know that shoots 6.8, the ASC mags are the most popular, along with whatever CProducts mags are left over. Because of cost, the PRI mags are the least popular, but are preferred by a few hand-loaders who are trying to squeeze every last bit of OAL from the very limited 43mm case length when trying to get better BC pills seated on top of as much powder as possible to make up for BC deficiencies the 6.8 SPC suffers from, again with just a little more velocity. You need .157" more OAL to get decent BC pills to fit in the 6.8, so that would require a magazine with a usable (not total) COL of 2.457".
If I was building a 6.8 to be competitive with the Grendel, I would spec a tighter twist barrel for the Berger 130 gr Match Grade Classic Hunter with a .497 G1 BC at velocities 400-600fps slower than a .270 Winchester (which would use a 10" twist for that bullet per Berger's recommendation), have a magazine made to allow a usable COL of 2.450", and use the LWRC Six8 receiver set....only I wouldn't waste the time with the 6.8 case because I could just take the Grendel and do the same, giving me more powder capacity, and the ability to load 130gr class pills out long, like the 129 SST, 130gr VLD, 130gr Swift Scirocco, 129gr Nosler Accubond Long-Range, or even the 123gr SST even faster. If LWRC actually ever sells the Six8 receiver set, imagine the requests they will have to make sure it doesn't say "Six8" anywhere on it. This hypothetical situation isn't possible for us right now, so it has zero relevance to the OP's purchasing considerations.
BC is more important than velocity
My .270 Winchester also has impressive velocities with 130gr at 3050-3100fps. It stays home and collects dust, while my .260 Rem pushing 130gr at 2800fps gets taken out regularly. The short answer as to why is BC, less recoil, and way less powder. Even a 6.5x55 Swede pushing 140gr at 2600fps will give you a higher hit probability on game than the .270 at distance because of less wind drift.
What makes sense to the consumer?
From a consumer standpoint, the Grendel does plenty fine with affordable hunting bullets from Hornady, while the 6.8 tries to compete with it using premium bullets that cost way more, and still fails to match the Grendel. The fact that the 6.8 is trying to be a Grendel says a lot about the whole debate, as you don't see a lot of Grendel owners loading varmint weight bullets and running them at 2800-2900fps, even though we can. There are 24 different factory loads for the 6.5 Grendel, so there is no need to reload for it. Most of my shooting sessions with it involve the 123gr A-MAX from Hornady, although I have boxed ammo from AA, Precision Firearms, and PPU/Wolf Gold Line as well. I'll never own all of the factory options for the Grendel, there are that many choices.
