[Nincomp]

Apparently the newer Grendel bolts on AR15's are a little more reliable than early-on, but they are still a weak area. Extractors are the weakest part and break fairly often. One of the problems is that the max chamber pressure for decent bolt life is 52,000 psi, which is well below where pressure signs on the case and primer normally appear. Reloaders who try to squeeze out maximum performance tend to add powder until they see pressure signs and end up with broken bolts, at least in AR15's.

Two of the advantages of the 6.8 SPC are its stronger bolt and its stronger case. It is considerably more tolerant of moderately overpressure rounds and the result of overpressure rounds tends to be poor brass life rather than poor bolt life. You can see the 6.8's beefier constructions near the base:

Some of the performance numbers that are posted for the 6.5 Grendel are from bolt-acton rifles which can utilize significantly higher chamber pressures. The 6mm ARC is based on the same case and Hornady publishes both "Gas Gun" and "Bolt Gun" loads. The "Bolt Gun" loads are at 62,000 psi, whereas the "Gas Gun" loads are at 52,000 psi.

 

[Hobbes96]

Apparently the newer Grendel bolts on AR15's are a little more reliable than early-on, on but they are still a weak area. Extractors are the weakest part and break fairly often. One of the problems is that the max chamber pressure for decent bolt life is 52,000 psi, which is well below where pressure signs on the case and primer normally appear. Reloaders who try to squeeze out maximum performance tend to add powder until they see pressure signs and end up with broken bolts, at least in AR15's.

Two of the advantages of the 6.8 SPC are its stronger bolt and its stronger case. It is considerably more tolerant of moderately overpressure rounds and the result tends to be poor brass life rather than poor bolt life. You can see the 6.8's beefier constructions near the base:
View attachment 75777

Some of the performance numbers that are posted for the 6.5 Grendel are from bolt-acton rifles which can utilize significantly higher chamber pressures. The 6mm ARC is based on the same case and Hornady publishes both "Gas Gun" and "Bolt Gun" loads. The "Bolt Gun" loads are at 62,000 psi, whereas the "Gas Gun" loads are at 52,000 psi.

I've wondered why the Grendel/7.62x39 case was used instead of the 6.8 case for the ARC; it seems to me the ARC would've been better off with the 6.8 case to start. Seating depth, which in turn affects case capacity; I'd assume, but, don't actually know.

 

[Woodstock]

Why did this have to be turned in to a Grendel vs 6.8SPC thread? Haven't we seen enough of those over the years?

 

[greentick]

It's been a while I guess.

 

[Nick M]

16" 6.8 spc the best I can find on a load chart

His channel is great. 2:40 in for our hero here.

 

[ozarkpugs]

Why did this have to be turned in to a Grendel vs 6.8SPC thread? Haven't we seen enough of those over the years?

You would think it was old news but there is a surprising amount of people new to the " larger than 5.56 " crowd that have not a clue what the facts are and fall for the " it's flatter shooting because of better BC . " hype . Just recently a couple of boys at the coffee shop/ general store had just built 16" 6.5gs for coyote hunting and we're telling me how I needed to upgrade from 6.8 to 6.5 . I didn't debate or even quote velocities I just suggested we compare the two using my chronograph and both factory SST ( what they shoot ) and hand loads of equal weight so I could see if the difference was enough to justify me swapping . I'm pretty sure I will not be replacing my 6.8s .

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[SOWACC]

I've wondered why the Grendel/7.62x39 case was used instead of the 6.8 case for the ARC; it seems to me the ARC would've been better off with the 6.8 case to start. Seating depth, which in turn affects case capacity; I'd assume, but, don't actually know.

The reason military went with an ARC in a Grendel case , is it shoulder set back makes longer bullets easier and more tolerable as far as case capacity is concerned. As pointed out earlier another advantage to the 6.8 brass is it is much better at preserving case for reloading. Two or three hot loads on Grendel and cases are pretty much done. It then gets into annealing and other issues preserving primer pockets. For Military it’s one and done. They sell their spent brass.

I do think think all the arguing and attacks on peoples mental acuity is totally out of line. Yes the Grendel case had advantages, yes the ARC has advantages over the Grendel. The 6.8 has advantages over both of these cases. It all comes down to what is the philosophy of use. Anyone who says the Grendel has no advantages over the 6.8 SPC is lying to themselves and anyone who says the 6.8 SPC has no advantages over the Grendel is lying as well.

Bottom line is if you are shooting at extended ranges and this is the primary philosophy of use, you would go Grendel. If are primarily hunting within 200 yds or using for self defense you go 6.8 . It’s just different primary philosophy of use. One fits better than the other.

For most sane purposes the 6.8 SPC set up has more advantages than Grendel. The Grendel has one real measurable advantage, down range performance. In order to get this though you are going to have to give up on a lot of advantages the 6.8 gives you.

Make your decision about what fits your philosophy of use and then go burn the barrel out and enjoy it. All the calling out of individuals who point out the obvious advantages of the Grendel and the surrounding drama serves no purpose. It does not promote discussion. It does not promote unity, it does not promote sharing of ideas. It is an attempt to promote suppression of thought.

I do not think that is why we have a forum. Forums are to promote free thought and exchange. I have all the calibers, my wife thinks I am a little touched. I have more reloading components for different calibers than carter has pills. Each rifle fits a different philosophy of use.

I’m open minded and I like to quantify the differences. So given what I want to accomplish that day will dictate what rifle in what cartridges I would use. That is the beauty of it all. If you can afford 20 different rifles with 20 different calibers great. Go for it. If you can afford one, that is great as well. Just be more particular in narrowing down just what your philosophy of use is.

Sometimes though it feels like you are entering a combat zone when we expound on different approaches to problems.
Just should not be like this. Every cartridge has pros and cons . Accept it and move on.

Everyone have a great day. Find what you like. Find what fits your philosophy and go use it.


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[Woodstock]

The reason military went with an ARC in a Grendel case , is it shoulder set back makes longer bullets easier and more tolerable as far as case capacity is concerned. As pointed out earlier another advantage to the 6.8 brass is it is much better at preserving case for reloading. Two or three hot loads on Grendel and cases are pretty much done. It then gets into annealing and other issues preserving primer pockets. For Military it’s one and done. They sell their spent brass.

I do think think all the arguing and attacks on peoples mental acuity is totally out of line. Yes the Grendel case had advantages, yes the ARC has advantages over the Grendel. The 6.8 has advantages over both of these cases. It all comes down to what is the philosophy of use. Anyone who says the Grendel has no advantages over the 6.8 SPC is lying to themselves and anyone who says the 6.8 SPC has no advantages over the Grendel is lying as well.

Bottom line is if you are shooting at extended ranges and this is the primary philosophy of use, you would go Grendel. If are primarily hunting within 200 yds or using for self defense you go 6.8 . It’s just different primary philosophy of use. One fits better than the other.

For most sane purposes the 6.8 SPC set up has more advantages than Grendel. The Grendel has one real measurable advantage, down range performance. In order to get this though you are going to have to give up on a lot of advantages the 6.8 gives you.

Make your decision about what fits your philosophy of use and then go burn the barrel out and enjoy it. All the calling out of individuals who point out the obvious advantages of the Grendel and the surrounding drama serves no purpose. It does not promote discussion. It does not promote unity, it does not promote sharing of ideas. It is an attempt to promote suppression of thought.

I do not think that is why we have a forum. Forums are to promote free thought and exchange. I have all the calibers, my wife thinks I am a little touched. I have more reloading components for different calibers than carter has pills. Each rifle fits a different philosophy of use.

I’m open minded and I like to quantify the differences. So given what I want to accomplish that day will dictate what rifle in what cartridges I would use. That is the beauty of it all. If you can afford 20 different rifles with 20 different calibers great. Go for it. If you can afford one, that is great as well. Just be more particular in narrowing down just what your philosophy of use is.

Sometimes though it feels like you are entering a combat zone when we expound on different approaches to problems.
Just should not be like this. Every cartridge has pros and cons . Accept it and move on.

Everyone have a great day. Find what you like. Find what fits your philosophy and go use it.


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Where has there been any arguing or attacks on anyone's mental acuity? The OP posted what he bought and why and you immediately tried to turn it into an argument about Grendel vs 6.8. Post #2 you said: "OK I will take up the challenge" where no challenge was offered to begin with and now that no one has agreed with you it is like you want to play the peace keeper for a fight you tried to start to begin with. Again, this is not arfcom and we don't play this nonsense here.

 

[SOWACC]

Where has there been any arguing or attacks on anyone's metal acuity? The OP posted what he bought and why and you immediately tried to turn it into an argument about Grendel vs 6.8. Post #2 you said: "OK I will take up the challenge" where no challenge was offered to begin with and now that no one has agreed with you it is like you want to play the peace keeper for a fight you tried to start to begin with. Again, this is not arfcom and we don't play this nonsense here.

Got it


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[Ducatim900]

Hmm, reading all this, just takes me back. Looking for an AR-15 platform, I read about the .223, 556 and then I came across the 6.8 SPC. Fell in love with it. Built the lowers, and the uppers are Stag left handed. 20.77 inch barrel and a 16. Bought a left handed 270 so I have bullets to play with for both guns.

In regards to how far it can shoot. I hunt in the woods. If you are lucky to get a clear 100 yard shot, you do it. With the trees and limbs, there is so much that can get in the way. I prefer the 95 TTSX to shoot. I will reload whatever I can get. It's one of my hobbies. Now I am going downstairs to reload 35 Remington. Note to self. Buy a 35 Remington. Can't get my brother to give up our dad's old 35 Remington.

 

[chewbacca]

That’s a slow 115gr load considering I get a 120 cavity back at 2500 out of a 12.5”.

Here is my actual dope from said 12.5” with that load.

I hunt/shoot suppressed so having a short barrel keeps the rifle handy. The 6.8 (loaded properly, not SAAMI neutered loads) smokes a 12” G, and both shouldn’t be used passed 300 (400 tops) anyway for deer sized game. This is why I chose the 6.8. My buddy has a 12” G and I load for his rifle, so I have apples to apples comparison.

 

[greentick]

What's your load data @chewbacca? I'm fixing to update the consolidated data and the 120mkz data is thin.

ETA: found it in an older post 27.5 loaded to 2.35" in a windowed mag.

 

[chewbacca]

Correct, 2200.

Also, I do shoot suppressed so there is a little free bore boost.

 

[Bull000]

Okay I'll accept the challenge comparing a 6.8 spc 115 making load to a 6.5 Grendel 120 gr pro hunter, not even going to use the 130 gr Nosler but just for some comparison. The objective being energy at 500 yards at sea level. 6.8 SPC 20" barrel seems we can get 2,590 out of it. At muzzle approximately 2,575 fps which equates to 1,693 ft lbs. Assuming 100 yd zero 10 mph crosswind . At 500 yards 1,396.8 fps, 496 ft lbs. Drop 4.17 mills drift , 1.92 mils.

For 6.5 Grendel 20" barrel, 120 pro hunter, we can get about 2,585 fps, 1,780 ft lbs. At 500 yds, 1,617 fps, 697 ft lbs, 3.63 mils drop, 1.39 mills drift. So at 500 yds the Gendels carries 221 fps more, 201 ft lbs more energy , .57 mils less drop, and. 53 mils less drift.

So the numbers speak. Is the Grendel better? Yes by a wide margin. . Is it enough to justify another boom stick? Depends what your shooting. Is the Grendel superior . Pretty much. Cheaper to buy a new upper that build a LR308? A lot. But it is subjective as to what all these numbers mean to different individuals. Enjoy the 6.8 it is a great rifle.

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My brain exploded.

 

[Yamaraja]

What's your load data @chewbacca? I'm fixing to update the consolidated data and the 120mkz data is thin.

ETA: found it in an older post 27.5 loaded to 2.35" in a windowed mag.

We load the 120 MKZ at 2.27 with 27.5 grains of AA2200 in our loaded ammo.
RL 10x 27.5 grains
H335 27.5 grains

 

[Yamaraja]

The Grendel bolt issue has never been fixed.
Grendel forums are still full of "what mags are reliable" posts.
The Grendel loads posted here are over pressure, you dont get those speeds at 52,000 PSI.
The 115 Sierra is the worst. bullet. ever. made for the 6.8. Hence why no one uses them.
Also why its always used in a comparison. Also usually Rem underpowered ammo

Heres the real numbers.
A 6.8 120 MKZ vs a 6.5 118 MKZ ( 16in barrel 6.8 and 20in 6.5) both hold 750 lb-ft of energy at 425 yards.
This with the Grendel at 52,000 PSI and the 6.8 at 58,500 SPCII pressures.
The BC difference of the 6.5 projectile cannot over come the pressure difference of the 6.8 SPCII

Now you all know I build bullets for and test both extensively.
I own 3 Grendels nowdays.
18in ARP barrel
22in Criterion barrel
18in McGowen barrel

Of course more 6.8s

The Grendel is fine for what it is. But its boasted up like a Creedmoor.

 

[41bear]

The Grendel bolt issue has never been fixed.
Grendel forums are still full of "what mags are reliable" posts.
The Grendel loads posted here are over pressure, you dont get those speeds at 52,000 PSI.
The 115 Sierra is the worst. bullet. ever. made for the 6.8. Hence why no one uses them.
Also why its always used in a comparison. Also usually Rem underpowered ammo

Heres the real numbers.
A 6.8 120 MKZ vs a 6.5 118 MKZ ( 16in barrel 6.8 and 20in 6.5) both hold 750 lb-ft of energy at 425 yards.
This with the Grendel at 52,000 PSI and the 6.8 at 58,500 SPCII pressures.
The BC difference of the 6.5 projectile cannot over come the pressure difference of the 6.8 SPCII

Now you all know I build bullets for and test both extensively.
I own 3 Grendels nowdays.
18in ARP barrel
22in Criterion barrel
18in McGowen barrel

Of course more 6.8s

The Grendel is fine for what it is. But its boasted up like a Creedmoor.

On your site you say your Grendel ammo, the 118 MKZ, does 2550 fps out of an 18 inch barrel versus your 68 SPC 120 MKZ does 2550 with no barrel length stated but I presume to be a 16 inch ARP "as you state above". I'm not questioning you but it seems to me that (and I own both 68 SPC and 65 Grendel ARP barrels along with SB's in both. Given the 2 inch difference of what, maybe 30/50 fps difference, is that deer/hog really going to know the difference? Dead is dead, right?

I like both and shoot both but my pride and joy are my 2 SIX5's which are both far more accurate, consistently, than any other upper I own.

 

[Nincomp]

The Grendel loads posted here are over pressure, you don't get those speeds at 52,000 PSI.

This is a point that a lot of people do not seem to understand, and it drives me nuts! Many reloaders rely on "pressure signs" like cratered primers or enlarged case-head while somehow believing that these signs only appear close to the SAAMI max pressure. These signs typically appear at significantly higher pressures, and loads showing no overpressure signs can still be well above SAAMI Max. Farther above SAAMI Max, in the case of the Grendel.

The fact is that SAAMI max pressures for both the 6.8 SPC and the 6.5 Grendel are based on the strength of a standard-diameter AR15 bolt, not their respective cases. It just so happens that the 6.8 SPC can tolerate moderate overpressure in the AR15 without damaging the rifle. That is a tremendous advantage for reloaders who like to load for max velocity and also for those who, like me, have been known to make the occasional mistake.

The Grendel and 6mm ARC cases are based on the 6mm PPC, which is routinely run well over 60,000+ psi. As I mentioned before, Hornady publishes 62,000 psi "Bolt Gun" loads for the ARC. Why on earth would the case say to itself: "Gee, I am in an AR15 today, so I think I'll start showing pressure signs 10,000 psi earlier"?

I am not saying that the Grendel is a bad cartridge. It is arguably easier to find high-BC 6.5 bullets and that might be important if you like to punch paper at 800 yards. When it comes to hunting though, I consider the 6.5 Grendel and the 6.8 SPC to be functionally equivalent.

 

[Strawdawg]

The fact is that SAAMI max pressures for both the 6.8 SPC and the 6.5 Grendel are based on the strength of a standard-diameter AR15 bolt, not their respective cases. It just so happens that the 6.8 SPC can tolerate moderate overpressure in the AR15 without damaging the rifle. That is a tremendous advantage for reloaders who like to load for max velocity and also for those who, like me, have been known to make the occasional mistake.

I believe it would be more correct to state that SAMMI pressures relate to the original specs for provided with the original SPC chamber and have no relevance to the chamber used by ARP, et al today that we call SPC II or whatever and which have no SAMMI approval or rating. Pressure testing was conducted and published by Harrison, Tim, Art of SSA, and HTG as I recall. Let's not put us into a breach of SAMMI corner as we are not.

 

[Yamaraja]

On your site you say your Grendel ammo, the 118 MKZ, does 2550 fps out of an 18 inch barrel versus your 68 SPC 120 MKZ does 2550 with no barrel length stated but I presume to be a 16 inch ARP "as you state above". I'm not questioning you but it seems to me that (and I own both 68 SPC and 65 Grendel ARP barrels along with SB's in both. Given the 2 inch difference of what, maybe 30/50 fps difference, is that deer/hog really going to know the difference? Dead is dead, right?

I like both and shoot both but my pride and joy are my 2 SIX5's which are both far more accurate, consistently, than any other upper I own.

The 6.8 ammo is rated in a 16in barrel.
However a 120gr 6.5 MKZ would only do 2500 fps in testing with an 18in barrel. Which is why I went with a 118gr, its the sweet spot to get the speed up.
So its really 100 fps + with the same barrel length and MKZ weight in the 6.8's favor.
The Grendel looses more with barrel length reduction than the 6.8 does. I have never tested a 16in Grendel so its all conjecture.

Functionally at 425 yards and 750 fb-ft of energy they are dead is dead equals. With the Grendel having a longer barrel.
However in functionality they are not. The 6.8 is more reliable. Bolt, extractor, mag etc.
As I have said I like them both. That is why I tried to build the best bullets we could for the 6.5G. As well as the 6.8 SPC.

Something I seldom see stated is while the 6.8 is very forgiving pressure wise the 6.5G is not.
When the 6.5G hits max pressures it does so very quickly. With a 6.8 you can look for pressure in .5 grain increments, a Grendel should be done in .2 grain increments.