12.5 is very handy and in 6.8 you can push it as fast as a 16" 6.5 . I agree with you that with factory loads and 20" barrels there is not a lot of difference but those that roll their own and like shorter barrels definitely benifit from going 6.8 .The passion...I love it.
Owning an 18" 6.8, and a 20" 6.5G I'll go on record with this (opinion):
From moderate barrel lengths and same ammunition, you won't see a difference in terminal ballistics on game. The velocity and energy is going to be within 5-10% of each other. Occasional outliers in experience will create some strong opinions about this however. Jim Bob and Joe Deer-Te both shoot a deer/hog in the shoulder with the exact same round...one hits the bone, the other narrowly misses, giving full pass-through..then they both run to their computer and either laud or bash the exact same bullet as if what happened in that instance is 100 percent repeatable.
Energy dump is great, especially on CNS shots where you are trying to sever the spinal column and nerves. Generally though, enough penetration to exit is something I'd prefer as it makes for much easier times tracking downed game.
As a dreaded G*****l owner, I don't understand the clique that runs the 12.5" SBRs or pistols. Again, in my opinion they are neutering the cartridge...and unless I'm just biased, I see a heck of a lot more hogs on video that either run off or take quite a few more rounds on average to drop with these rigs. But I will never tell anyone why they can't purchase and run what they want.
I generalize down to this: If you want a 14.5-16" barreled rifle, the 6.8 gives a hair of an advantage usually. 18" kind of appears to be the dead-even ground. If you want to stretch out the range (and your barrel another 4-6", the Grendel maintains a bit of an edge.
Terminal effects can be altered by choice of bullet.
Neither of these cartridges are so much better than the other that you should sell your stuff and switch over.
Good stuff! I just read a different article that compared the 6.5 and 6.8. It also touted the 24" barrel for the 6.5 G and the 16" barrel for the 6.8 SPC. It wasn't until the very end did the guy mention if you have both in a 16" barrel that the 6.8 was better. He did however come to the conclusion that in a short barrel in a CQB type of environmet the 6.8 was better and for long range shooting in a longer barrel the 6.5 was better. When the USSF and the US Army Marksmanship team along with Remington researched these rounds the 6.8 was the clear winner. Your conclussion is correct. Even now, the USSOCM has determined that the 6.8 x 51 is the preferred round over the 5.56mm, 6mm, 7mm, 7.62mm and the 6.5mm. One of the biggest factors was penetration on barriers and class IV body armor. For long range, they have chose the 6.5mm Credemore.The writer of that article is either ignorant or has an agenda / bias. Hornady specs 2590 fps for their 6.5 Grendel 123gr SST from a 24" barrel. That's about 2390 FPS from a 16" barrel in typical 4-grove configurations. Hornady specs their 6.8 SPC 120gr SST in a 16" right out of the gate at 2460 FPS. Also remember that nearly all commercial 6.8 loads are loaded light to avoid issues with the original flawed SPC I chamber, there are still some floating around. There's a lot of headroom available for 6.8 hand-loads, milspec loads or custom loads like Wilson Combat etc. that you can't achieve with 6.5 Grendel.
Anyway, using an ARP 3R barrel (for which many 6.8 user run) you'll push another 60 FPS to 100 FPS faster than the specs. Lets go on the low end at +60 FPS. On an ARP barrel, the SST factory load will push 2520 FPS from the muzzle. Out to 500 yards, 6.8 is either pushing higher KE or drops to the same KE as 6.5 by 500 yards. But I digress, KE is not a useful predictor of terminal performance. It only shows us the available energy, not how well it is used upon impact which is what really matters. I also agree is Constructor that SD is meaningless. It has no value in determining terminal performance what so ever.
I also have yet to find any 3R nitrided 6.5 Grendel barrels except the couple left overs on ARP's site which are not in production any longer. So pretty much all Grendel barrels are standard 4 grove, mostly stainless, nitrided or chrome lined, you'll get the expected velocities, but not more.
Finally and most importantly, the US military disagrees with the results of that article as well. Some yahoo on the internet using theoretical numbers apparently knows more about terminal performance than the US Military's AMU who tested over 10,000 rounds of live ammunition during the development of 6.8 SPC.
See the attached reports of testing done by the US military including using actual 120gr OTM 6.5 Grendel loads (Hornady OTM projectiles) against 115gr OTM 6.8 SPC loads (also Hornady OTM projectiles of the same design) through auto glass at 100 yards....Terminal performance is something is that massively over-looked and poorly understood by nearly all of these purported "experts". Most people equate Kinetic Energy (KE) with "stopping power" when KE is meaningless without knowing how the projectile acts when impacting and traveling through the target body.
6.8mm projectiles simply performed better than 6.5mm projectiles of the same construction type at similar velocities, both through barriers and directly impacting the target. While 6.8mm projectiles may loose energy a little faster than 6.5mm, they consistently provide better terminal performance. 7mm projectiles provided even more terminal performance than 6.8mm, however accuracy was lower and velocity loss was even faster. 6.8 provided the best middle ground. It may seem strange than 0.3mm in diameter affects how it acts upon impact, but it does. I suspect that's a threshold where 6.5mm doesn't have enough drag when traveling through the target to reliably expand and rapidly dump its energy.
I get sick and tired of people parroting "6.5 has lower drag" without realizing that while low drag is beneficial for exterior ballistics, it's NOT beneficial for terminal ballistics. You want HIGHER drag on impact...logical fail. So you have to balance velocity loss while in flight with fluid resistance upon impact. Bigger bullet leave bigger holes, but loose energy faster and have less ideal drop characteristics.
KE alone has little real value in evaluating performance. Momentum is more useful predictor than KE without consideration to projectile design. The primary factors are 1. shot placement 2. penetration depth followed by 3. terminal performance (aka leave as big of a hole as possible). 6.5 offers no meaningful advantages at usable ranges of either cartridge for #1 or #2, but 6.8 delivers better on #3.
Well said!Bottom line is if you are talking about killing paper farther than most people ever shoot paper and don't mind a long heavy barrel then the 6.5 is your best choice . For all other uses the 6.8 is superior in every way . ___ I personally don't think anyone who can't comprehend that should not be looked at as an expert or even a halfway knowledgeable source of information .
I agree with your dissertation. I originally was looking at the 6.5 Grendel, but after much reading, I have a 6.8 now. There is a lot of good information on the slide show and PDFs you provided. Anything over 500m is long range to me when it comes to rifles. I am more convinced then ever, that I chose the right caliber in the 6.8 SPC. Especially for what I am going to use it for.Right, terminal performance favors larger diameter bullets, you WANT high drag when it passing through the target body. Exterior ballistics (aka the characteristics of it in flight through the air) favor skinnier longer bullets (low drag, many 6.5mm based cartridges). Bigger projectiles simply cause more damage to the target, but loose energy faster while traveling through the air. You can compensate by using more powder and a bigger case, but that increases recoil and cost while also lowering ammo capacity to the soldier.
But what good is it to have 100,000 ft-lbs of energy if it never gets dumped into the target? 6.8mm projectiles really do perform better when impacting the target than 6.5mm projectiles of the same construction, the real data is there and irrefutable from multiple sources. But application dictates what properties are more desirable. If your just trying to land shots at very long distances and have some terminal impact on the target even if non-ideal, the simple act of actually getting the bullet to hit the target is more important than how it performs when it hits the target (aka favoring bullets that have better trajectories).
At closer ranges or even medium ranges, how the bullet acts when it hits the target is of a higher priority. 6.5 G does NOT retain enough velocity to expand past 400 to 500 yards with even the best projectiles and hottest hand loads, even then performance is degraded compared to 200 or 300 yards. Neither does 6.8 SPC. Both have about the same range where they are within expansion thresholds unless you use the military loadings of 6.8 that may extend that range another 50yds or so (they run about 2650 to 2700 fps for 110gr milspec hot loads from 16" barrels), but either way it does not make it a long range cartridge nor was it ever intended to be.
BTW, for those saying 6.5 G is a "long range cartridge" compared to 6.8 SPC, well the 6.5 G projectile has the muzzle energy of a .22 Long round at those ranges...won't expand and is traveling slow enough you can actually see it pass by on a normal camera...drop is hundreds of inches...long range my butt! You want long range, try .338 Lapua. That is highly lethal at 1k yds still.
I would say 6.5 Creedmoor is more of a medium range large game and long range target cartridge. It doesn't have the velocity at 1k yds to expand either. You need some serious power for very long ranges like .338 Lapua, .50 cal BMG etc. 6.5 G and 6.8 SPC are both medium to short range small frame AR cartridges for medium (aka deer, hogs, humans) and some larger game (with proper loading). 6.5 G does have more emphasis on long range target use while 6.8 SPC has more emphasis on terminal performance as it's intent was a medium and short range combat cartridge to replace 5.56 which has performance issues at both ranges even with the best loads, especially through barriers which is important for combat performance.
If you look at the actual Kinetic Energy dump wave forms from brass fetcher (see below / attached), you'll see .50 BW provides the best performance by far between 6.8, 6.5 and 5.56...at least at close range. Problem is, that projectile is just that, one that focuses on maximizing single shot performance all else be damned.Y’all all forgetting that the article stated that the 350 legend is as good or better than the other 3!!🤔