308 vs 6 ARC & 6.5 Grendel

[Bakwa]

Let's beat this horse while it's down.

It cannot be disputed that 308 produces more energy down range when compared to its small frame counterparts.
But for all practical purposes have any of you guys that hunt, target shoot, or obsess over in flight & terminal ballistics regretted moving from a large frame 308 to a small frame in 6mm ARC or 6.5 G for the weight savings. I know there are a lot of things which we can debate on paper, but for those that have actually traded the terminal performance for the weight savings, were your results on game or bad people, splash on steel targets, visible bullet trace, etc..., diminished to the point where you regret the trade off.

 

[DeathBeforeDismount]

At one time I had like 8 .308 rifles.

I now own 0.

The question is pointless unless you define what you want to do and what you want from the cartridge.

If you want a semi auto large frame, 6 or 6.5c are the obvious choices.

In small frame 6 arc by a country mile.

Energy doesn't mean shit if you can't put the bullet where it needs to go and a higher bc bullets will retain more energy at distance while being much more forgiving of wind calls. It will also be easier to shoot and spot your shot.

 

[Skeptic1]

I think the OP's question is worded well. I wish I had more experience with the smaller framed calibers so I could give an educated opinion on the matter.
I do ponder sometimes how that when the 6.5mm and 6mm (choose your acronym) cartridges became so popular that the 308 suddenly became inadequate at doing all the things that it had previously been so good at.

 

[DeathBeforeDismount]

308 was never "so good". It's always been a compromise. The only reason for the popularity was it being the standard military round for a number of years and still a NATO round today. The problem was the better options were not optimized for faster twist rate and modern bullet selection is much better today. Factory rifles had very limited options. Guys were running .260s 20 years ago and kicking .308s ass. A custom .243 with a fast twist barrel was the original 6 creed long ago. Modern bullets like the 185 jugger and copper solids have actually made the .308 much better than it was...but that same tech applies across the board so it's not like it gained any ground.

That doesn't mean the 308 won't kill or can't be used for long range. There are just much better options and not many situations where the .308 is a superior option given current offerings.

The 6 and 6.5 became popular when novices realized they like hitting targets...and high level shooters take advantage of that performance edge to win. Also less recoil makes them much easier to shoot and friendly to new shooters.

 

[Bakwa]

At one time I had like 8 .308 rifles.

I now own 0.

The question is pointless unless you define what you want to do and what you want from the cartridge.

If you want a semi auto large frame, 6 or 6.5c are the obvious choices.

In small frame 6 arc by a country mile.

Energy doesn't mean shit if you can't put the bullet where it needs to go and a higher bc bullets will retain more energy at distance while being much more forgiving of wind calls. It will also be easier to shoot and spot your shot.

I don't see the question as pointless as it stands.

I want the opinions of hunters, target shooter, and comp guys alike. All of which have people who have made a switch in the last few years to experiment with a small frame setup over large frames. Everyone is seeking good enough for their intended purposes.

Yes, 6mm CM will far outperform 6 ARC at longer ranges, but at the cost of weight. What I want to know is where these individual's draw that line with their desire for a lighter/handier setup.

I do appreciate your responses and agree with pretty much all of your conclusions.

Cheers

 

[charnicus]

I personally am fast tracking a 6ARC now. I was really close to picking up a large frame 6.5. It seems worth checking out. I have a bolt gun for longer rounds.

 

[thedude824]

My experiences are all over the place. I’ve got a 16” barrel for my SCAR 17 I occasionally use. I’ve also got a 24” 308 barrel for my MRAD. I just finished an 18” 6.5 Grendel. If I’m wanting the greatest accuracy and precision and the weight/size isn’t prohibitive. I’ll always grab the MRAD. That rifle makes everyone look like a precision marksman. My next choice would likely be the 6.5 Grendel. It’s lightweight makes accurate shooting a little harder for me, but I tend to keep the SCAR in its 13” configuration since these two cover the two main diverging criteria that determine which rifle I grab. The MRAD with the 169 SMK is outstanding out to 1k. I haven’t tried the other two to that distance. I would need to become a MUCH better shooter on a semi to approximate my accuracy with my MRAD. I’m still not convinced the the MRAD isn’t enchanted. I’m not a good enough shooter to produce the groups I regularly produce with it.

 

[45-90]

I own both 2, 6mm ARCs and 8, 308s.
I like the 6 mm ARC, no interest in the 6.5 Grendel, and the 308 is still a better caliber for most endeavors.
My light weight 6lb 2oz 308 with 16" barrel shoots about 100 fps faster with similar BC bullets .523 308 168 gr VS .536 6mm 108 gr and the 6mm ARC has a 18" barrel 2" longer and the AR 15 is 8 lbs 14 oz.... heavier than the AR 10 with its longer Proof barrel and rifle stock....the carbine 6 mm ARC is a bit lighter but still heavier than the lightweight AR10.
But compare the AR 10 18" Proof with Areo furniture is 9 lbs 2 oz....not much different the the AR15 with a rifle stock at 8 lbs 14 oz same barrel maker Proof same length 18".

The light 308 16" is capable of 2840 ft/lbs if muzzle energy.
The 18" 6mm ARC has 1700 ft/lbs of muzzle energy with 2" extra barrel.

The 308 is capable of flatter trajectory, and much more energy, with the 2" less barrel.
Plus the 308 16" can shoot 208 ELDM at 2440 fps mag length...for lots of LR energy and much less wind drift at 1000 yds than the 6 ARC.
I like both and enjoy shooting both,...both are super accurate, with good barrels.

So I'll continue to use both, but the 308 is a better all around cartridge with modern powders.
The 6 ARC has a bit less recoil, the 308 has cheap LC brass plus cheap bullets or tons of quality brass and bullets.
308 cartridges available everywhere...and can operate at higher pressures than the 6 mm ARC or Grendel in an auto loader...as the 308 can run the same pressure as its bolt gun counterparts.

 

[Old Man with Gun]

You have to consider the firearms as a whole and the intended purpose. There is no way a large frame will complete against a small frame in run and gun. Weapon handling favors smaller, lighter, higher capacity and lower recoiling.

The large frame will dominate at longer range as you can shoot the same bullets from either, but with significantly more velocity with a larger cartridge.

Hunting coyotes, doesn't matter, big hogs, probably will.

I own small frames in 9mm, 223, 300BO, 6.5G, and 458 SOCOM. Barrel lengths from 5" to 24'. Each is better at something than all the others.

I only have one large frame, a SP-10 in 6.5C but also several bolt guns in that caliber. Once I get to the larger cartridges I prefer bolt guns for the precision at distance.

 

[Bluedog82]

I’ve shot deer with .308, 6.5CM, 6 ARC, .300blk, and .223. All of them died just fine. The .300blk kill was a broadside doe at about 25yds, 150gr SP out of a 6” barrel. She ran maybe 20yds and dropped. The .223 (11.5”) was a neck shot at 10yds that dropped in its tracks. The 18” 6ARC was a quartering toward shot at 245yds through the front of the chest. Ran 100yds or so.

 

[ut755ln]

Let's beat this horse while it's down.

It cannot be disputed that 308 produces more energy down range when compared to its small frame counterparts.
But for all practical purposes have any of you guys that hunt, target shoot, or obsess over in flight & terminal ballistics regretted moving from a large frame 308 to a small frame in 6mm ARC or 6.5 G for the weight savings. I know there are a lot of things which we can debate on paper, but for those that have actually traded the terminal performance for the weight savings, were your results on game or bad people, splash on steel targets, visible bullet trace, etc..., diminished to the point where you regret the trade off.

At one point I had several iterations of the 308, all in bolt guns. I now no longer have any and I have moved to the small frame 6 ARC platforms. I currently own two, an LMT conversions with a D Wilson barrel and a Geissele GFR.

I find that self spotting on the 6 ARC has not been a problem but I have only gone to 1k yards once and I usually shoot it inside of 600 yards. To me, I am not sure that what you are doing is the right comparison. The 6 ARC is a way to improve the range, accuracy and lethality of the 5.56 small frame gas gun specifically. The fact that you are shooting a sub 10 lbs rifle and it has similar ballistic characteristics to a .308 gas gun is pretty amazing.

I think 308 should really be compared to other offerings in a large frame gas gun. The military recently adopted the 6.5 cm in their MRGG bid and again it is because they put a more modern, better designed, higher performing cartridge into the rifles and extended their range/accuracy ect.

Since I tend to shoot inside of 600 yards most of the time, there is really no need for me to pursue the larger frame/caliber 6.5 cm. This next part is purely my opinion but I have never had much trouble killing hogs/deer/coyotes with a 5.56. When they did not drop it was almost always bad shot placement on my part. It was very rare when I got a good heart/lung shot that any of them would run much. My go to hog gun now is the 14.5" Geissele in 6 ARC and so far nothing I have shot with it has run off (knock on wood). I do try to be ethical when I take shots and I have not shot at anything past 300 yards with this setup so far but would be comfortable taking a shot farther. The exit wounds with the 6 ARC are more substantial than the 556 (no surprise) and it clearly does more soft tissue damage.

 

[vmpglenn]

I currently shoot a POF Rogue 16" .308 (AR15 sized but shoots .308), 6.5 Grendel (18", 13.9") and 6mm Max (14.5").

The Rogue is light for a .308 and recoil is an issue if you're trying to spot your own shots at distance. I'd take it hunting for larger game but follow-up shots would be slower (just light any light .308).

I've been shooting Grendel for decades, and it is a fantastic do-all cartridge. Recoil, especially suppressed, is easily managed and you can spot your shots. Higher SD bullets than 6ARC give you more flexibility when hunting, and you can't beat the factory ammo offerings -- including the $0.70cpr stuff from AAC. I'm excited for the ICAR mags coming from Magpul - I already have a LWRCi Six8 receiver set.

6Max is basically a pussycat with recoil but you get 100gr 6mm bullets going 2600fps out of a 14.5" barrel. With a suppressor, 6Max is basically recoiling like a 5.56 gun. Ray Helms is winning DMR matches with 6Max and it is definitely a contender for comps in general due to its recoil characteristics and flat trajectory. I'm not a huge fan of the cost of ammo, which is sort of an issue for 6ARC as well.

I handload for all 3 cartridges using Ramshot TAC, which makes it easy not to mix up powders! 178 ELD-X for .308, 120 Barnes Match Burners for Grendel, and 103 ELD-X for 6Max. I enjoy shooting Grendel the most. Easily managed recoil, great performance out to the 600yd max range I have available, and I can lose a few spent cases and not feel bad about it.

 

[LRRPF52]

Let's beat this horse while it's down.

It cannot be disputed that 308 produces more energy down range when compared to its small frame counterparts.
But for all practical purposes have any of you guys that hunt, target shoot, or obsess over in flight & terminal ballistics regretted moving from a large frame 308 to a small frame in 6mm ARC or 6.5 G for the weight savings. I know there are a lot of things which we can debate on paper, but for those that have actually traded the terminal performance for the weight savings, were your results on game or bad people, splash on steel targets, visible bullet trace, etc..., diminished to the point where you regret the trade off.

Nope. I’ve owned a bunch of different AR-10s and consider myself a mega-geek AR-10 aficionado since the 1980s. I always wanted an AR-10 something bad back then, but all we had were Dutch import parts guns without the original lower receivers because they were select-fire. I thought almost all hope was lost.

Then KAC came along, in collaboration with Eugene Stoner himself, and introduced the SR-25 series. I couldn’t believe it. I wanted an SR-25K so bad I could taste it. When I was stationed in DC as a young PFC, I saw an SR-25 at a local Virginia gun store, but couldn’t snatch it on a PFC’s salary. That year, the Clinton AWB was passed and the prices started doubling on anything pre-ban. The pre-ban SR-25Ks were made in a lot of 100 limited editions, and they got even more out of reach for me.

Before the ban expired, I eventually got an ArmaLite 24” free-float rifle for shooting LR. Awesome rifle that grouped astonishingly-well. I later got a DPMS LR-308, an LR-260, and then had GA Precision just build me what I wanted from then-on in both .308 and .260 Rem. Amazing rifles that shoot phenomenally-well and actually run.

DPMS LR-308 in Häyhä 2007, Finland

I later got a DPMS SASS upper and a Savage MSR-10 impulse buy.

I’ve shot, competed with, and spotted boat-loads of .308 M118, M118LR, M852, and 155gr Scenar hand loads over the past 30 years now, so I am very familiar with what a .308 sounds like when it impacts steel. That is a sound that brings joy to my ears.


FinnSniper 2008 top 3 placements, GAP custom-built .308 w/ Hensoldt 3-12x56

I got into a 16” 6.5 Grendel barrel/bolt combo back in 2009, dipped my toes in the water with it just to kinda see what it was like, wasn’t really impressed at first with velocities, as I was primarily shooting .260 Rem at the time for LR. When I tried shooting it at 1200yds, I was shocked at how predictable it was and how easy it was to self-spot.

So I started getting higher-end pipes and building and shooting more of them and it really displaced almost all of my .260 Rem and .308 shooting. A 123gr 6.5mm hitting steel almost sounds like a 168gr SMK from .308, but you can just watch it go in yourself even with a lightweight AR-15.

I wish something like it had been available back in the 1980s and 1990s. I get way more loads on brass than I do with .260 Rem, and there are tons of factory loads that are all meant to run in gas guns, unlike .308 Win and .260 Rem.

So now I have a bunch of Grendels from 24” down to 8.5”. I focused on 16” from 2009-2014, then a 17.6” Lilja and a bunch of others from 2014-2017. Then I built 2x 12” Grendels meant to be suppressed and have primarily shot the 12” alongside 17.6” and 18” LaRue since then. I really enjoy the 12” Grendel out of all the AR-15s, M16s, and M4s I have shot since 1987.

10.5” Grendel

If I were to standardize my armory with one type of AR-15, it would be the 12” Grendel, suppressed with TBAC, Bootleg carriers, and some other things.

 

[ut755ln]

@LRRPF52 have you noticed any change in accuracy with the bootleg bcgs? For that matter any issues with them?

 

[Bluedog82]

@LRRPF52 have you noticed any change in accuracy with the bootleg bcgs? For that matter any issues with them?

Not him, but I have a .308 that I’m very impressed with.

 

[LRRPF52]

@LRRPF52 have you noticed any change in accuracy with the bootleg bcgs? For that matter any issues with them?

They just allow you to adjust the cyclic rate for the load and suppressed use. They are my go-to carriers nowadays.

I put one in the 8.5” Grendel as well, so I’ll have some more data forthcoming as I work with that over the next 3-7 years.

I have had zero issues with them so far, dating back to 2017. I also dropped one in my 17.6” Lilja Grendel as it was gassed a bit hard with some loads. 18” MLGS Grendels are like a teeter-totter when you go down to lower bullet weights sometimes, so opening up the gas allows you to tune it to for the load.

For 18”, ILGS with a bit larger port is a better way to go I think. I have 18” Grendels coming out of my ears, so I never got an ILGS.

 

[Old Man with Gun]

I have a bunch of the bootleg BCGs and they are my go-to as well.

 

[thedude824]

They just allow you to adjust the cyclic rate for the load and suppressed use. They are my go-to carriers nowadays.

I put one in the 8.5” Grendel as well, so I’ll have some more data forthcoming as I work with that over the next 3-7 years.

I have had zero issues with them so far, dating back to 2017. I also dropped one in my 17.6” Lilja Grendel as it was gassed a bit hard with some loads. 18” MLGS Grendels are like a teeter-totter when you go down to lower bullet weights sometimes, so opening up the gas allows you to tune it to for the load.

For 18”, ILGS with a bit larger port is a better way to go I think. I have 18” Grendels coming out of my ears, so I never got an ILGS.

What buffer system and buffer weights are you using with your Bootleg carriers?

 

[LRRPF52]

What buffer system and buffer weights are you using with your Bootleg carriers?

Standard carbine buffer, extra power carbine spring in the 12”.

I think I still have a standard spring and buffer in the 17.6” Lilja barrel Grendel. I’ll have to look at it.

 

[Old Man with Gun]

What buffer system and buffer weights are you using with your Bootleg carriers?

I start with standard and adjust depending on how it runs. Hard to guess before you try any particular combo of barrel and suppressor.

 

[hlee]

I have 3 6.5 grendels and a 22arc. I’m a believer, if not a fanatic. But, it’s as true in firearms as it is in automobiles. There’s no replacement for displacement. That’s why I have a couple of 308s, a few long action rifles, and a few magnum action rifles as well. The grendels are much more fun to shoot, but the magnums have their place, and so do those in between.

 

[Longshot85]

Lots of people in here with far more experience using AR's long range than me

I'll drop this vid link mainly because 1. I was interested in results of both 6 ARC and 6.5CM in 14.5 in configurations and 2. both rifles were same barrel length

I have no idea if this dude is on here or not and I have zero affiliation with him or any gear in the video.....merely passing along

I have a 16 inch AR10 6.5cm I built so this gave a good heads up on capabilities

 

[Ledzep]

Let's beat this horse while it's down.

It cannot be disputed that 308 produces more energy down range when compared to its small frame counterparts.
But for all practical purposes have any of you guys that hunt, target shoot, or obsess over in flight & terminal ballistics regretted moving from a large frame 308 to a small frame in 6mm ARC or 6.5 G for the weight savings. I know there are a lot of things which we can debate on paper, but for those that have actually traded the terminal performance for the weight savings, were your results on game or bad people, splash on steel targets, visible bullet trace, etc..., diminished to the point where you regret the trade off.

EDIT: Ledzep is idiot. I thought it can be disputed but it can't .

No ragerts. I tried building .308 and 6.5 Creedmoor AR-10's and never could make one that I liked. Heavy "precision" rifles down to super-light weight 16" rifles I could never love using them. Tried to. Couldn't get there. My first 6.5 Grendel builds had me sold on that, and I've been drinking 6mm ARC coolaid since I first learned about it (~1-2 years before release).

For most of what I do, either of the smaller calibers handles it. A 16" ARC or Grendel offers enough bullet at enough velocity to hunt pretty much any medium/large game smaller than elk. The only situation I'd like the larger cartridge is very close range (<100yd) very large game (elk+ or something dangerous, brown bear or whatever).

 

[B Man]

Nope. I’ve owned a bunch of different AR-10s and consider myself a mega-geek AR-10 aficionado since the 1980s. I always wanted an AR-10 something bad back then, but all we had were Dutch import parts guns without the original lower receivers because they were select-fire. I thought almost all hope was lost.

Then KAC came along, in collaboration with Eugene Stoner himself, and introduced the SR-25 series. I couldn’t believe it. I wanted an SR-25K so bad I could taste it. When I was stationed in DC as a young PFC, I saw an SR-25 at a local Virginia gun store, but couldn’t snatch it on a PFC’s salary. That year, the Clinton AWB was passed and the prices started doubling on anything pre-ban. The pre-ban SR-25Ks were made in a lot of 100 limited editions, and they got even more out of reach for me.

Before the ban expired, I eventually got an ArmaLite 24” free-float rifle for shooting LR. Awesome rifle that grouped astonishingly-well. I later got a DPMS LR-308, an LR-260, and then had GA Precision just build me what I wanted from then-on in both .308 and .260 Rem. Amazing rifles that shoot phenomenally-well and actually run.

DPMS LR-308 in Häyhä 2007, Finland

I later got a DPMS SASS upper and a Savage MSR-10 impulse buy.

I’ve shot, competed with, and spotted boat-loads of .308 M118, M118LR, M852, and 155gr Scenar hand loads over the past 30 years now, so I am very familiar with what a .308 sounds like when it impacts steel. That is a sound that brings joy to my ears.


FinnSniper 2008 top 3 placements, GAP custom-built .308 w/ Hensoldt 3-12x56

I got into a 16” 6.5 Grendel barrel/bolt combo back in 2009, dipped my toes in the water with it just to kinda see what it was like, wasn’t really impressed at first with velocities, as I was primarily shooting .260 Rem at the time for LR. When I tried shooting it at 1200yds, I was shocked at how predictable it was and how easy it was to self-spot.

So I started getting higher-end pipes and building and shooting more of them and it really displaced almost all of my .260 Rem and .308 shooting. A 123gr 6.5mm hitting steel almost sounds like a 168gr SMK from .308, but you can just watch it go in yourself even with a lightweight AR-15.

I wish something like it had been available back in the 1980s and 1990s. I get way more loads on brass than I do with .260 Rem, and there are tons of factory loads that are all meant to run in gas guns, unlike .308 Win and .260 Rem.

So now I have a bunch of Grendels from 24” down to 8.5”. I focused on 16” from 2009-2014, then a 17.6” Lilja and a bunch of others from 2014-2017. Then I built 2x 12” Grendels meant to be suppressed and have primarily shot the 12” alongside 17.6” and 18” LaRue since then. I really enjoy the 12” Grendel out of all the AR-15s, M16s, and M4s I have shot since 1987.

10.5” Grendel

If I were to standardize my armory with one type of AR-15, it would be the 12” Grendel, suppressed with TBAC, Bootleg carriers, and some other things.

Before I reply an opinion I want to acknowledge this man’s experience with the platform and cartridge. It can not be argued it works.

 

[B Man]

The opinion, simple.

If you are handloading with temp stable powders then pick one, flip a coin a shoot it. 6 arc has no advantage with any really good temp stable powders I am finding out.
For hunting and steel 6.5 Grendel, purely steel 6arc, for love of a 30cal 308 ar10.
The Grendel is a lighter packaged 308win. The 6 arc with factory ammo is the more hot rod for the best ballistics LR if running factory ammo.
Honestly, the three are so close though it does not matter much. I can outpace and on a hit challenge connect more repeatedly at 900 yards With my 20” 6 arc with 108 eldm’s. For for the life of me I just love the hell out of my 308 win 16” with 178 eldm’s. It would be THE rifle I grab.

6.5 Grendel

6 arc

308 win cold bore shot

Edited to add when I said purely steel in 6 arc, do not think I am not acknowledging it as a great hunting cartridge

 

[LRRPF52]

My whole interest in AR-10s since the 1980s was an AR-10 “CAR-15” concept of a lighter, more compact carbine but in 7.62 NATO.

I never realized that goal because I got into long barrel AR-10s for shooting LR.

My youngest son has been asking about when we’ll get to shoot the .308s, so I’m sure it will happen eventually.

It would be fun to do an XM177E2 style build in 7.62 NATO, using a smaller frame receiver size.

My focus is on 8.5” Grendel though for the time being.

 

[TonyTheTiger]

Let's beat this horse while it's down.

Nah.
There's nothing we could cover in this thread that hasn't been covered ad nauseum in the other 50 threads on the subject.

 

[Jsp556]

You’re not going to see much difference in terminal performance shooting small and medium game unless you’re regularly shooting them past 400 yards.

You will see a difference in how much easier the Grendel and ARC’s are to shoot, spot, and get a quick second shot off on running pigs or coyotes.

 

[Makinchips208]

I think it can be disputed. 110gr A-tips or 109 ELD-M's vs. any .308 match bullet that will fit in an AR-10 magazine at some distance (although it may be 500+yd) is going to catch up on retained energy barrel length for barrel length. From muzzle to target the gap is shrinking.

Can you provide numbers or proof? Cause im thinking that 6arc probably doesnt even come close to 308 even at 1000, talking energy only.

From what i see, a 168 in a 308 always has more energy than a 108 in 6arc within 1000 yards. Even more so if they have equal barrel lengths.

Yes “the gap is shrinking” but i think even to nearly 1500 a 308 has more energy.

Other than that? Yeah i think 6arc and 6.5 Grendel both are stellar.

 

[Bakwa]

Nah.
There's nothing we could cover in this thread that hasn't been covered ad nauseum in the other 50 threads on the subject.

Yeah, but if we could recap it all in one thread. T’would be helpful for everyone. Would it not?

 

[Old Man with Gun]

Can you provide numbers or proof? Cause im thinking that 6arc probably doesnt even come close to 308 even at 1000, talking energy only.

From what i see, a 168 in a 308 always has more energy than a 108 in 6arc within 1000 yards. Even more so if they have equal barrel lengths.

Yes “the gap is shrinking” but i think even to nearly 1500 a 308 has more energy.

Other than that? Yeah i think 6arc and 6.5 Grendel both are stellar.

Why the focus on energy? Is it intended to rank one cartridge over another for effective hunting kills. If both cartridges do the job well, they are equal.
I am more concerned if there are accurate bullets with the right combination of expansion and penetration at the impact velocity I expect.

As long as you can punch paper, see splash and hunt at ethical ranges, what is the advantage of more energy?

 

[diggler1833]

Having killed at least a hundred pigs with the .308 and again with a 6.5 Grendel, I'll share my opinions on terminal performance.

(Terminally) The .308 is a clear winner. CNS shots are going to produce equally good results, but when you start shooting runners and hitting poorly, that is when you'll notice the difference. I actually documented fewer shots to recovered pigs with a (cheap) .308 bullet, than I did with the expensive 6.5 projectiles...same with the 6.8 SPC.

I had a significantly higher ratio of shots to the vitals where an animal dropped in place (like a CNS hit) with the .308 too. It occasionally happened with the Grendel, but it occurred about 25% of the time with the .308.

My bottom line after watching the footage and counting the hits etc... is that the .308 with a 35 cent soft point is going to outperform the small frame guns with 80 cent bullets.

*****

Now, if you're going to be primarily target shooting, it isn't a bad idea to step down. Not only is the .308 going to give you a weight penalty, but also a recoil one, and BC disadvantage too.

 

[db2000]

25CM SP10

 

[Old Man with Gun]

I rarely hunt anymore, but I had no complaints with my 6.5G on hog, coyotes etc. when I did. I used 123g SST @ 2,600. For much of what I did, having a handy rifle with fast follow up shots was important. I'm sure a few that made it a short distance would have been DRT with my SP-10 in 6.5C, but I wouldn't have gotten off as many shots and we were trying to get rid of many pests as we could. No big hogs where I was either. I think the biggest we got was 135lbs. I guess it depends a lot on the environment and the game.

 

[TonyTheTiger]

Yeah, but if we could recap it all in one thread. T’would be helpful for everyone. Would it not?

Maybe, but I'm not sure how you'll achieve that. This thread will end up with all the same rabbit trails and random opinions as all the other threads.

 

[Makinchips208]

Why the focus on energy? Is it intended to rank one cartridge over another for effective hunting kills. If both cartridges do the job well, they are equal.
I am more concerned if there are accurate bullets with the right combination of expansion and penetration at the impact velocity I expect.

As long as you can punch paper, see splash and hunt at ethical ranges, what is the advantage of more energy?

Why focus on energy? Only because a claim was made about the retained energy of 6arc.

Whats the advantage of more energy? Not much if you make a neck shot.

 

[six67]

I went with 6.5grendel for hunting. 6mm would be fine too but it excels over grendel at 400y+ where i wouldn't take a shot anyway. There used to be dirt cheap wolf steel ammo and that sealed the deal for grendel for me. Wolf is not very cheap or available now so it would be a harder decision between 6 and 6.5.

Easy to make a 6arc or 6.5g around 5lbs before optic. I have some 308s and even the lightest one is still kinda heavy. And the parts cost more and also aren't as readily available in stock or on sale to replace parts if you damage them in the field.

 

[Ledzep]

Can you provide numbers or proof? Cause im thinking that 6arc probably doesnt even come close to 308 even at 1000, talking energy only.

From what i see, a 168 in a 308 always has more energy than a 108 in 6arc within 1000 yards. Even more so if they have equal barrel lengths.

Yes “the gap is shrinking” but i think even to nearly 1500 a 308 has more energy.

Other than that? Yeah i think 6arc and 6.5 Grendel both are stellar.

Good call. I'll edit my post. I got wires crossed. Everyone gets to be an idiot sometimes.

ETA: Just remembered why. The original purpose was to achieve greater terminal performance (energy delivery), not necessarily retained energy. The leg up is the way the 106 TAP bullet performs vs. issued OTM designs for down-range terminal. When you go low-drag hunting bullets on both you're going to get better terminal with the .308. Trajectory will be slightly better on the 6mm ARC, wind drift will be better on the 6 ARC.

 

[Makinchips208]

Good call. I'll edit my post. I got wires crossed. Everyone gets to be an idiot sometimes.

ETA: Just remembered why. The original purpose was to achieve greater terminal performance (energy delivery), not necessarily retained energy. The leg up is the way the 106 TAP bullet performs vs. issued OTM designs for down-range terminal. When you go low-drag hunting bullets on both you're going to get better terminal with the .308. Trajectory will be slightly better on the 6mm ARC, wind drift will be better on the 6 ARC.

Yer not an idiot. Far from it.

Makes sense on that bullet. Thanks for the clarification.

And for the sake of the thread, the advantages of 6arc (and 6.5grendel?) with their advantages and increased hit potential over 308, we could say a lower energy hit is better than a high energy miss?

 

[Bakwa]

Maybe, but I'm not sure how you'll achieve that. This thread will end up with all the same rabbit trails and random opinions as all the other threads.

You’re probably right.
This thread is probably no more than analytical masturbation for me inspired by boredom. I’m lazy as well, so that doesn’t help.

I still thank everyone for their responses and hope to continue these conversations as this thread is giving me things to ponder.

Carry on gents.

 

[45-90]

It's really a non argument the 308 W wins, for most hunting and shooting applications.
Their are a few gaming areas in timed events where 223 or 300 blkout would be better.
Here is a 6 lb, 16" 308 starting a test with various 155 gr bullets over 2800 fps.
The 168 eldm at 2756 fps shooting 1/2" 5 shot groups, with flatter trajectory.
The 16" 308 has 1100 ft/lbs of advantage over my 108 gr 18" 6 ARC.
The 208 gr eldm at 2442 fps brings the energy and much less wind drift, longer supersonic range.

For killing game its like the difference between the 338 WM and 308 win, when comparing these small AR cartridge to tbe 308.

The large frame AR can run 300 WSM and 338 RCM at full power book loads around 65,000 psi. I own one....(as pictured a 338 RCM) not limited to the weaker low pressure AR 15 bolts.

The 338 RCM would be a better cartridge than the 308 of lage game were considered.

last pic a mag full of 208 eldm .691 BC, much more potent and better BC than the 6 mm AR or 6.5 Grendel.

Cheap to shoot...
A thousand rds of primed LC, (who cares if ya loose it brass) plus factory seconds will kill a truck load of hogs...loaded on a Dillion progressive, and still capable of fine accuracy as the targt pictured.

So you can make a AR 10 308 light like 6 lbs, it has much higher operating pressure safely in the AR platform, larger diameter, even better BCs in some bullets.

And most anyone can handle 308 recoil.

Making the 308 W the easy winner for most applications.
It would be illogical to argue against the evidence presented.
But you can own whatever caliber ya want for what ever purpose ya want...choice

Still like my 6 mm ARCs but for many serious things the 308 is better, like for hunting.
Many deer and most everything has been killed with a 22LR, but there may be better choices...I'd choose the Grendel or 6 ARC over the 22LR for that endeavor, but some may not under certain circumstances.
Your choice...

 

[AR-180]

@45-90,

I see the one recipe. Can you share some more data and groups? Are you using any special upgrades to your 308? That’s pretty incredible performance.

This is a great thread.

 

[45-90]

To get the 308 AR 10 light, I used a JG carbon fiber handguard, a magnesium upper, titanium muzzle brake, titanium bolt carrier, WC 16" fluted recon barrel, Areo lower with Minimalist stock, and 1 oz titanium muzzle brake was machined at home for free, but are available without making your own.
Shop sales, prices very, look for discounts, Back Friday and "Deals".


Load data is in the Speer #15 Manual, 2000MR is the top velocity powder.
It's accurate and fast in several barrels I own.
Change powders when going over 200 grs.
Like the 208 grs at 2442 in the 16" barrel...but there is a cut off area may be 208 Berger still up to snuff with 2000MR.

ROAM has magnesium, lowers, and uppers for AR 10 build...
Or they offer a 5.48 LB AR 10 rifle called Red River for those who don't build their own, with a pencil barrel.

I did not go for the pencil barrel, the few I seen or used are not accurate, instead I chose a slightly heavier 16" WC fluted barrel. A medium priced barrel that often is very accurate in other calibers I own...but no guarantees, I had to send one back after scoping it.

You can use cheap LC brass and still shoot 3 bullets through the same hole, 5 shots around 1/2" sometimes less with this light setup.

Anyone can build a light, accurate 308, and do the same thing if they care to.

 

[B Man]

The 168 eldm at 2756 fps shooting 1/2" 5 shot groups, with flatter trajectory.
The 16" 308 has 1100 ft/lbs of advantage over my 108 gr 18" 6 ARC.
The 208 gr eldm at 2442 fps brings the energy and much less wind drift, longer supersonic range.

What load are you using for 2750 from a 16” barrel with 168’s? 2000mr but what charge weight?

 

[rlsmith1]

Let's beat this horse while it's down.

It cannot be disputed that 308 produces more energy down range when compared to its small frame counterparts.
But for all practical purposes have any of you guys that hunt, target shoot, or obsess over in flight & terminal ballistics regretted moving from a large frame 308 to a small frame in 6mm ARC or 6.5 G for the weight savings. I know there are a lot of things which we can debate on paper, but for those that have actually traded the terminal performance for the weight savings, were your results on game or bad people, splash on steel targets, visible bullet trace, etc..., diminished to the point where you regret the trade off.

This summer I plan to shoot 14.5" 6 ARC and 6.5 CM side by side as much as possible. I really like the ARC but if I can get more energy on target while still having a manageable platform, I'll likely go that route.

6 ARC Pros:

• Good (relatively cheap) factory ammo
• High BC bullets
• Small frame
• Sounds very nice suppressed

6.5 CM Pros:

• Stronger bolt
• More common ammunition (tbd if cheap PSA ammo is accurate enough)
• High BC bullets
• More energy on target

My gut tells me to get the 6.5CM where I want it I'll need to shoot the FGGM 130 AR Hybrids, but the $1 / round AAC ammo with decent bullets should be good enough for practice. Have been shooting 80 ELD VT's mostly in the ARC for coyotes but I'll also shoot 108's and 103's this summer too

 

[45-90]

What load are you using for 2750 from a 16” barrel with 168’s? 2000mr but what charge weight?

You can see the charge weight in one photo...But you are encouraged to go get the Speer reloading manual #15 and work up to their maximum loads, which is what I did, to be safe and see if its the right powder for your needs.
Each barrel is different my 16" is almost as fast as the 18" in 308.

 

[B Man]

You can see the charge weight in one photo...But you are encouraged to go get the Speer reloading manual #15 and work up to their maximum loads, which is what I did, to be safe and see if its the right powder for your needs.
Each barrel is different my 16" is almost as fast as the 18" in 308.

Mine runs fast for 16”. But I have not came close to this with 2000mr without pressure. My 24” barely got to those speeds without pressure. Why I was asking what charge you are using.

 

[45-90]

Mine runs fast for 16”. But I have not came close to this with 2000mr without pressure. My 24” barely got to those speeds without pressure. Why I was asking what charge you are using.

Page 416 Speer reloading manual 168 gr bullet almost 2900 fps in a 24" barrel and over 3000 for the 150 gr....I'm using a .5 grain to .3 grain under their max load.
No problem with pressure. But it is a max load or close to it, obviously, and should be worked up to.
These are my normal 308 manual loads...I use 30" barrel, long action, and hybrid cases if ya want to go 3255 fps for a 168 gr. In 308 win.

 

[Bakwa]

This summer I plan to shoot 14.5" 6 ARC and 6.5 CM side by side as much as possible. I really like the ARC but if I can get more energy on target while still having a manageable platform, I'll likely go that route.

6 ARC Pros:

• Good (relatively cheap) factory ammo
• High BC bullets
• Small frame
• Sounds very nice suppressed

6.5 CM Pros:

• Stronger bolt
• More common ammunition (tbd if cheap PSA ammo is accurate enough)
• High BC bullets
• More energy on target

My gut tells me to get the 6.5CM where I want it I'll need to shoot the FGGM 130 AR Hybrids, but the $1 / round AAC ammo with decent bullets should be good enough for practice. Have been shooting 80 ELD VT's mostly in the ARC for coyotes but I'll also shoot 108's and 103's this summer too

I understand your dilemma.
There is a part of me that wants to jump on the MRGG-A band wagon and get a 14.5” 6.5cm barrel for my MWS. Shave the rails off and lighten it a bit… it will still probably be a heavy beast though.

 

[ut755ln]

Page 416 Speer reloading manual 168 gr bullet almost 2900 fps in a 24" barrel and over 3000 for the 150 gr....I'm using a .5 grain to .3 grain under their max load.
No problem with pressure. But it is a max load or close to it, obviously, and should be worked up to.
These are my normal 308 manual loads...I use 30" barrel, long action, and hybrid cases if ya want to go 3255 fps for a 168 gr. In 308 win.

When I read stuff like this, it makes me want to go down the reload rabbit hole so bad.