The 6.5 Grendel vs 6.8 SPC debate can get ugly.
However, I’m not out to bash either of them because there’s ZERO reason to. They are both Fantastic cartridges that allow the AR-15 to perform FAR beyond what it was originally designed for.
But they are different.
So I’m going to explain the differences between them WITHOUT any childish “my cartridge can beat your cartridge” talk.
Then I’m going to explain why it doesn’t matter as much as everyone thinks it does.
(Honest disclaimer: I like the 6.5 Grendel better, but the 6.8 SPC is an amazing cartridge)
First of all, The VAST majority of us don’t reload. As such I’m going to limit myself to factory ammo only.
Before 6.8 fans cry foul because of the 6.8 SPCII chamber, remember that the Grendel II chamber exists, and has the exact same amount of performance increase over the original Grendel.
(Both the 6.5 Grendel and 6.8 SPC were released with less than ideal chamber dimensions. These were corrected on BOTH of them. The changes allow for a roughly 100-200 FPS increase in velocity with BOTH cartridges)
That’s data only reloaders really need. The rest of us (me included) will be buying factory ammo. So again:
I‘m comparing factory ammo only and basing performance on that.
So, shall we?
6.5 Grendel vs 6.8 SPC: Ballistics
If you don’t know what Sectional Density is, I HIGHLY recommend reading My article on Sectional Density before continuing. Now that’s out of the way.
6.5 Grendel wins in Sectional Density. The 6.8mm bullet is larger than the 6.5mm bullet. There’s no getting around that.
You’ll be hard pressed to find 6.8 SPC ammo heavier than 120 grains (Sectional Density .223), but it does exist. 6.5 Grendel is available in factory loaded ammo up to 129 grains. (Sectional Density .264)
Neither cartridge does it’s best with heavier bullets though, and here’s why.
Notice how far the bullets stick into the case? Heavier bullets are even longer, and longer bullets mean less space for gunpowder. That means lower bullet velocities.
(Someone will ask “What about the SSA 6.8 140 grain loading?” First, it requires a SPCII chamber. Second, it’s longer than case spec at 2.300 inches vs the spec 2.260 inches. It MUST be loaded longer than spec or the ogive will be below the case mouth)
Anyway.
The 6.5 Grendel gets the optimum balance of velocity to bullet weight at around 100- 123 grains. The 6.8 hits this balance in the 100-120 grain range.
- The Grendel can do 123gr bullet Bullets with a Sectional Density of .252.
- The 6.8 SPC highest is .223 with 120gr bullet.
Higher Sectional Densities mean more aerodynamic bullets.
Fortunately, Hornady produces both the 6.5 Grendel and 6.8 SPC in their SST bullet (accurate, low drag hunting ammo) so we can compare them “apples-to-apples“. 123 Grains for the Grendel, 120 Grains for the SPC. Both velocities are out of 16” barrels.
Here’s what their trajectories look like:
Bullet “A” is the 6.5 Grendel. Bullet “B” is the 6.8 SPC
The 6.8 starts out 100 FPS faster. They’re almost identical at 250 Yards, and the Grendel is 100 FPS faster at 500 yards. Otherwise, until about 500-600 yards, they’re isn’t much difference.
Thanks to it’s more aerodynamic bullet, The Grendel and SPC are neck and neck for a long way even with the 6.8 SPC starting 100 FPS faster.
Move the barrel lengths up, the Grendel will start to take a more significant lead… But not enough to leave the 6.8 in the Dust. And that brings up another point
The 6.8 SPC’s Great Virtue AND Great Fault
The 6.8 really doesn’t gain a lot of velocity from barrels longer than 16″ inches. This is both a blessing and curse. It allows great performance from short barrels. However it doesn’t really allow you to get more velocity from a longer barrel. (you get some, but not as much a 6.5 Grendel)
This chart shows them starting at the same velocity (the 6.5 Grendel 24″ barrel velocity, which I suspect is around the 24″ 6.8 velocity, but I haven’t found data to support that)
Bullet “A” is the 6.5 Grendel. Bullet “B” is the 6.8 SPC
The Grendel’s lead widens a little, (about 200 FPS faster at 500 yards) but not enough to ignore the 6.8 SPC. Most 6.5 Grendel vs 6.8 SPC loadings will have similar results. (almost identical until about 400-500 yards where the Grendel gains an advantage)
For those who love the SSA 140 grain 6.8 SPC loading, let’s match it up against the 129 Long Range Accubond out of a 6.5 Grendel (available here) I’m assuming 24″ barrels on both.
Bullet “A” is the 6.5 Grendel. Bullet “B” is the 6.8 SPC
That narrows the gap considerably. Note the trajectories are within 5 inches all the way to 1000 yards. The velocity crossover point is just over 500 yards. Note: the 6.5 Grendel still drifts less in the wind. (please also note that this 6.8 SPC loading requires a SPCII chamber and special magazines. The Grendel loading is in spec for length and doesn’t have a Grendel II chamber)
I can sum up all three charts like this: inside common hunting range (20-200 yards) there is ZERO effective difference. Let me say that again:
Inside common hunting range there is ZERO effective difference.
If you want a Tactical Cartridge, things don’t really change because there’s ZERO effective difference in lethality.
Both are VERY lethal. (assuming good shot placement)
The only real differences show up at longer ranges. The Grendel drops less and more importantly, the Grendel Drifts less in the wind.
The 6.5 Grendel drifts 6-7 inches less at 500 yards depending on barrel length. Not a lot, but it might be the difference between a hit and a miss.
Further out, things change.
The 6.5 Grendel drifts up to 19 inches less at 750 yards. That’s a huge difference in ability to land shots at long range. Granted, that’s a long way and most soldiers couldn’t hit an enemy at that range.
But don’t forget:
In Afghanistan, half of the combat took place under 300 yards. (where they are basically dead even)
A further 30% took place between 300 and 600 yards. (even until 500-ish yards then slight advantage Grendel because of drop and drift)
about 20% took place between 600 and 900 yards. (where the Grendel wins because it drifts less in the wind)
It doesn’t matter how you slice it, beyond 500 yards the Grendel has an advantage because it’s going faster, drops less and drifts less in the wind. That’s inherent in high sectional density bullets: they are more aerodynamic.
However, the differences don’t show up until 400-500 yards, and they aren’t large.
Which brings me to part everyone misses.
Neither animals nor enemy soldiers can read the headstamp on your brass.
They don’t care.
Both combat and hunting are about the same thing: Accuracy. You can’t miss fast enough to win a gunfight or fill a hunting tag.
That’s why I like the Grendel better. The 6.5 Grendel isn’t more accurate than the 6.8 SPC. They are both VERY accurate cartridges. However, the long, high Sectional density 6.5 mm bullets ignore the wind better and retain velocity better.
Less wind drift = better shot placement at long range.
The 6.8 is no slouch, but 6.8mm bullets can’t buck the wind like 6.5mm bullets because the 6.5mm bullets have a higher sectional density.
Another huge component of accuracy is practice.
Here the Grendel also has an advantage in cost of ammo. As I write this in October of 2015, the cheapest 6.8 SPC ammo is around $0.75/round. That’s for just plain old FMJ, which is best for punching paper because it’s not effective for hunting or combat.
You can buy Grendel Ammo for only $0.28/round.
FYI: If you buy after clicking most of the product links on this page I'll make a few bucks. It's not much, but it keeps the website going and I would appreciate your support. 🙂
A little math tells me that 6.8 SPC is almost 3 times more expensive than Grendel. Plus, that $0.28/round Grendel ammo is Wolf’s 100 grain “military classic”, which is constructed like the infamously lethal 7N6 bullet. It’s deadly stuff.
However, don’t get so wrapped up in the “which cartridge is better” debate that you lose some crucial focus and forget an all important truth:
Your ACCURACY matters WAY more than the cartridge you pick.
I would suggest working on your accuracy because You can’t miss fast enough to win a gunfight or fill a hunting tag.
(NOTE: One of the most accurate 6.5 Grendel barrels is also one of the least expensive. It’s made by Saturn, has the improved Grendel II chamber, a reputation for excellent accuracy, and comes with a matched bolt of very high quality. It goes out of stock regularly, so I would grab one when you can.)
P.S. To the Grendel and SPC Fanboys: Girls you’re both pretty. Now can you stop bickering and move along?
you gave me just the info I wanted, with no BS and Ballistic data to back it up. This offically pushes me to the 6.5 so long as I can source ammo or reloading equipment. I know it’s a older article but I just wanted to say thanks for telling it like it is.
Thanks. 🙂 Also, everyone is welcome to comment on any article here, regardless of how old it is.
I went with 300 blk on my alternate build, but I think on the next one it’s 6.5. Thanks for the article.
Your figures are are off by quite a bit by my own testing with the Hornady 120SST factory load. Velocities confirmed with two different chronograph.
120SST factory load
1) Wislon Combat 16″ 1-11″ twist 4 groove mid gas= 2510fps average velocity
2) AR Performance 20″ 1-11.25″ twist hybrid 5R rifle gas= 2620 average velocity
So with those numbers what would you surmise the 24″ barrel velocities to be considering my 20″ barrel is quite easily surpassing you 24″ estimate.
They are both great rounds and if I was looking for a pure paper puncher I would most likely go with the Grendel and keep my loads mild enough as to not have to worry about breakage.
But I use my rifles for hunting and am quite impressed with the 68SPC for that purpose with either spec I or spec II loads as long as it isn’t Remington factory ammo.
Ammo availability and selection in my area is another key issue for me with factory ammo I can always find Hornady 68SPC on the shelf.
Okay, using your numbers my basic point changes very little. The two cartridges are more alike than different. The Grendel and SPC both throw similar weight bullets at similar velocities. The SPC starts faster, the Grendel keeps it’s speed better and drifts less in the wind.
Giving the SPC a little more velocity only makes the two rounds even for longer.
Let’s guess the 24″ SPC gets 2700 FPS with the 120 SST out of your barrel. (120 FPS faster than the Grendel, about the same difference as with the 16″ barrels) They’re still pretty even until about 500-600 yards.
The 6.8 SPC is a GREAT hunting cartridge, and the 6.5 Grendel is too. Again, they’re more alike than different inside 400-600 yards.
I am running a 22in ARP Triad with 130 grain Berger Classic Hunters and VLD’s
These are running in the 2830 fps range with 34.4 Grains of LEVER.
The Grendel cannot touch them. Do the math on that.
When you put hand loads into the equation the 6.8 moves up a lot over factory ammo.
This is why you never see the comparison done with hand loads to hands loads between the 2 cartridges.
That is a potent loading. Do you know what pressure it’s running at? I ask because I’ve seen lower 6.8 SPCII velocities being called very hot handloads.
He’s faster than my 22″ .260 Rem with 130gr Berger VLD, and I’m using way more powder than that, at or slightly over the edge of working pressure for .260 Rem, which is higher than 6.8 SPC.
Must be working with a new set of physics the rest of us have not learned yet…
…or is a brave hand loader with promising results on the chronograph outweighing safety.
Interesting article. Based on what I know about the 6.8, its more similar to the 6.5 Grendel than most know. Both are great cartridges IMO. But for hunting, the 6.8 is the better choice due to the shorter barrel length as mentioned on your article. The 6.5 Grendel can also be hard on bolts too. And that FMJ ammo you’re were talking about, I’ve seen it as cheap as $9.99 a box. For punching paper at distance, I’d probably pick the Grendel over the 6.8. Or even better, one of the newer 6.8 Wildcats or a 270AR. But those are Wildcat cartridges for now.
Nice article with practical advice. Liked the technical considerations you provided for powder capacities, chamber pressures, chamber design, factory vs hand loads, etc.
One, non-technical term was mentioned a couple of times when discussing wind drift. No bullet “bucks the wind.” More aerodynamic bullets produce less drag and lose less velocity during flight. Less wind drift by a bullet is due to less time in flight due to a higher average velocity for the flight.
It’s true that “bucks the wind” is an entirely slang term with no real world meaning. However, bringing up Form Factors, G7 vs G1 drag profiles, and flight time was beyond the scope of the article (no pun intended) so I used slang.
Also, don’t forget that flight time is only part of the wind drift equation, and a small part too. The bullet’s shape is more important than flight time. Example: look at the 16″ barrel chart, you’ll see that at 250 yards, the Grendel has less wind drift even though the 6.8 has a shorter flight time at 250 yards. (because it started faster)
Well, Abe. It was time for me to go back to “school.” You are absolutely correct. Bullet aerodynamics are what matters unless flight times are significantly different. I was severely over-simplifying the phenomenon of bullet flight in moving air.
That is what I learned be spending a couple of weekends studying all eleven sections of exterior ballistics at http://www.exteriorballistics.com/ebexplained/index.cfm
I had to dust off a couple of my engineering textbooks but it was worth it. I have a whole new appreciation for long distance shooting.
Thanks.
One point your article does not mention, and I only bring this up because it’s somewhat important only in self defense scenarios, is that the design of the 6.5G cartridge causes a higher rate of feeding malfunctions. Keep in mind the guys who came up with 6.8 tested 6.5 but discarded it “due to reliability concerns” which may have also included the bolt issue with 6.5G. If you are a long range shooter than by all means 6.5G is the better cartridge. But I am a firm believer that for 0-500 encounters with human opponents, 6.8 is the bullet I want in my rifle’s chamber. I still have about 120 rounds of the 140 grain Bergers too.
Do you have a credible source for the Grendel feeding problems? I’ve heard that objection many times but haven’t found solid evidence for it.
Also, the 6.8 SPC and the 6.5 Grendel were both introduced at the 2004 SHOT show. Given that, how could the 6.8 designers reject the Grendel design if they didn’t know about it?
Incorrect. The guys who concocted the 6.8 thought there was some terminal performance advantage to a bullet with a .007″ larger diameter, with lower impact speed and less chance of hit potential. They were offered professional assistance at the AMU, but refused it, and chose one of the worst bullet diameters possible for the case length of the SPC.
This is the first I’ve heard someone pull that argument out of the air, and I’ve been following the program from the start before it was even known to civilians, to include assistance with assembly of some of the original uppers, before they even had a 6.8 magazine, where we were told that it ran fine using 5.56 mags with a different follower. That proved to be bogus, with all sorts of malfunctions, indicative of a low-rate, unprofessional program of marketing to military units, with no testing to back up their claims.
Within 500 yards, a shorter barrel Grendel has higher hit potential than the 6.8 all day long, due to BC. Within 175yds using the same barrel length, 120gr SST vs. 123gr SST, there is more retained energy and impact speed with 6.5 Grendel, but not much practical difference. Within 250yds, the 6.5 Grendel SBR still is within PBZ, whereas the 6.8 is not because of wind drift.
Interesting article. For sure the 6.8 was purpose built for a shorter barrel, the 6.5 for a longer barrel. Putting a longer barrel on the 6.8 regardless of bullet weight won’t recover the difference in BC. Example the Hornady 120/123 bullets the 6.5 has a BC of .510 the 6.8 .400. Big difference which manifests itself like you said in the 300-600 range. For handloading with a properly headspaced and matched bolt/barrel assuming my magazines will allowing longer OAL of the cartridge I still like the 6.8. My barrel is a ARP 20″ with 6.8 ARP chamber (similar to Wylde) allowing for for customizing of the load and OAL (all subject to ability to fit into the magazine. With those variables I think you’ll find the 6.8 to be about dead even with the 6.5.
Farther out and I’m .338 Lapua with its HUGE BC 600-2000.
Zzzzt! Nomenclature of the charts above throws everything into question. First, the bullet “drop” normally refers to the actual drop of the bullet from the muzzle downward over distances in charts, and “path” is the position of the bullet above and below the ZERO point (2nd line of intersection between a straight line out of the barrel and the bullet arc). Are you zeroing at 100, 200, or what in this chart? Clearly the chart must mean PATH not DROP. And obviously there is NO DROP at the muzzle! Now, a 120gr SST launched at 2460fps yields a DROP of 100″ at 500 yards, at sea level, 70 degrees F, 29.85″ barometric pressure, not the 74″specified here. Zeroed for 200 yards, it has a 64″ drop, so clearly it is referring to the PATH based on some intermediate ZERO distance. OR it’s just 26″ off in it’s calculations. Drift in a 90 degree 5MPH wind is 14″. Where did 22″ come from?? Mine are based on Nikon’s ballistic program. Also though it might be the same for both cartridges, what it the wind speed?? Not specified anywhere I can see. So anything other that the relative velocities vs. energy in these charts are suspect and should be double checked by the reader. Velocity vs energy disregarding distances, etc., seem to be about right. I won’t go into the other holes (pun noted) I see here.
All of these cartridge limitations are based on the assumption that we are limited to an AR15 platform. Okay, fair enough. ARs are fun, no doubt. But one should first ask why establish that limit? Because of weight? Because they’ll carry 20 rounds? You don’t need a mag larger than 5 rounds for hunting. Human wave attacks, and battles well that’s another story. It seems that people are looking for a “one size fits all” solution. Small light weapon, little recoil, able to take on 20 humans at a time, or kill an elk at 400 yards. Seems like nonsense to me to ask one cartridge to fill all these roles. One autoloader solution I have for hunting is a BAR in 270 Win. Good out to 500 yards with authority, semi auto 4+1, heavier and longer than an AR15, but not so burdensome that I can’t hike 10 miles / day in the mountains with it and a backpack, and I’m over 60 y/o. Shoots cloverleaves with handloads @100 yards. 130gr SSTs or TTSXs, 2940fps. But indeed I’m interested in a 6.5G for target shooting and hunting out to 200 yards of wild pigs. Remember, you want some margin for error in the form of power when hunting unless you limit yourself to close enough ranges to guarantee head or neck/spine shots. Authoritative anchoring is important in my book. Just my H.O.
For me, the benefit is once I go through the legality of owning an AR lower, I can simply change the upper receiver and I have a zombie gun, a range gun or even a hunting gun all in one platform. That is something you cannot do with a BAR.
One point you seem to gloss over is fact that different barrels (twist) don’t necessarily favor the same bullet weight. My 6.8 Rem gives sub MOA with 110 grain bullets. With heavier weight bullets the groups open up to 3+” at 100 yd.
One of the most overlooked aspects of shooting, hunting, and charts is wind drift. We really don’t focus as much on drop, because we are going to use some common method to compensate for drop. Even within common hunting distances, you will find that wind drift is your main determining factor in point blank zero (PBZ).
That’s where we hand the rifle to our wife, nephew, niece, uncle, etc., and tell them to aim right behind the deer’s shoulder, and slowly pull the trigger straight, back, to the rear with the crosshairs/red dot aligned with the vitals. With a 200yd zero, drop within 400yds is very similar, but drift limits the lower BC projectile to a shorter PBZ, while also increasing the likelihood of a miss of the vitals with a wind shift.
Chambers: There was and is no deficiency with the 6.5 Grendel SAAMI chamber. That is an incorrect statement peddled by PTG reamers, so he doesn’t have to worry about holding himself and his monkey shop to industry standards. Once he convinces you that he has a better reamer design, he can now send you whatever he likes, with no way of most shops being able to verify, so don’t fall into that trap.
6.5 Grendel SAAMI chamber works extremely well, and is one of the only chambers I know of that shoots different bullet shapes the way it does into MOA or less. Normally, rifles I have had custom built are throated for one specific ogive shape, usually some kind of VLD or secant ogive bullet that I will stick to in that gun. With 6.5 Grendel, both tangent and secant ogive bullets shoot equally well.
Another big difference between 6.5 Grendel and 6.8 is twist rate. 6.8 simply does not as tight of a twist, and RPM on terminal performance is beneficial to nose deformation, rapid expansion, and multiple helical wound cavities within the same length of penetration space.
So even within 200yds, you get more speed on contact with the tissue or barrier, less deflection, more penetration, more wound cavity helix within the medium, and more likely hit through the intended aiming point (POA).
For the guy pushing his 22″ 6.8 to 2830fps with a 130gr, that’s faster than a 22″ .260 Remington or 6.5 Creedmoor, both of which operate at higher working pressures than the 6.8, with way more case capacity. Something doesn’t add up there.
Shorter barrels? 6.5 Grendel is still superior in every parameter you can measure, despite what has been claimed. People just don’t have a basic understanding of physics, so they have to rely on other uneducated people to form their opinions for them, which are incorrect.
Both of these cartridges were designed for very different purpose. They are NOT and apples to apples comparison, as you try to portray above. The 6.8mm was specifically designed as a system that would not lose much if any velocity therefore range from barrels under 16″ down to 10″. Even the 8.5″ PSD can still be effective out to 300m due to this design.
The 6.5 on the other hand was made specifically for long range shots out of an AR-15 system, with long barrels, for precision shots out to 1000m. What the 6.5 possesses in long range, it loses when used in super short barrels.
These are two completely different tools, that you should pick depending on mission requirements. I went with 6.8 because I wanted a 10.5″ barrel that would still be lethal to around 450m. I would pick a 6.5 if I wanted a DMR style rifle with long barrel to make long range shots. You are right about one thing at the end, both cartridges are very attractive, but one out shines the other, only depending on your usage.
I’ve been very enraptured with the 6.5 caliber ever since I bought a Swedish Mauser chambered in 6.5×55. it is, in my honest opinion, the most accurate bullet diameter out there. I really enjoyed your article. I’m about to start building a new AR and I’d been debating between 300 blackout, 6.8, and 6.5. Hoping to make a dual function hunting and target rifle.
Jeez my brain hurts now ! I am an average joe that just wants to hunt blacktail, muleys and porkers with a AR platform (DS Arms lower).backed with a RockRiver 2 stage trigger and currently sporting a Fulton Armory 20″ match grade bull barrel. This is my bench set up.
I’m looking for a complete upper that I can just swap and go. Places I hunt in CA. mostly offer short shots 20-100 yds but sometimes out to 150-300, nothing over. I mostly track n stalk so weight and length are prioritized and some of the territory is thick stuff with clearings here and there and good humps
Mag capacity cant be more than 10 rounds any way so that issue is mute. I will buy new mags anyway.
You Gentlemen seem very honest and knowledgeable so which caliber would be recomended ? I reload for my bolt guns so ammo availability is not an issue but I am justa novice.
Looking in the range of 5-600 $ maybe a bit more.
Sooooo… all input is appreciated. Going complete upper so I can hold only one outfit responsible for warranty, etc.
Thanks again !