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If you recently purchased the barrel, then it's a SPEC II as listed on their website. I haven't heard of anyone selling new 6.8 barrels that are the old SPEC I.

Most 6.8 barrel group decent, except some brands like Bear Creek which can be hit or miss. With that said, you can't go wrong with an ARP barrel. Every ARP barrel I've owned groups 1/2" or less depending on the load.

BTW: Welcome to the forum.
 

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Thanks bubba, that's great info. The barrel is stamped SPC but they sold and sick by it as SPC II. Kind of confusing but I read the reviews for ARP's and that's why I pulled the trigger on it. Fired a few rounds today to start seasoning the barrel and I was honestly impressed. I thought the Grendel was my new fav but this six eight I built is one heck of a steel ringer and is making me warm up to it as my deer rifle for within eighty yards or so. Killed a deer with my Grendel on my property this past season. Entry and exit were almost the same size but the vitals were turned to mush. Ran maybe forty yards. From what I've gathered, the 6.8 should drop em on the spot within eighty yards. Owning a small chunk of mountain with few places clear past that distance, that six eight should reign as King of the Mountain. Again, thank you and the others but one for your input
If you already have a 6.5 Grendel upper why did you build a 6.8? Out to 500 yards they are within 100 FPS typically with similar projectile weights and BC's. Past 500, 6.5 is better for paper punching, but neither offer expansion past 400 to 500 with the best loads. Or was it just for fun? I'm curious.
 

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Discussion Starter #24
If you already have a 6.5 Grendel upper why did you build a 6.8? Out to 500 yards they are within 100 FPS typically with similar projectile weights and BC's. Past 500, 6.5 is better for paper punching, but neither offer expansion past 400 to 500 with the best loads. Or was it just for fun? I'm curious.
First reason:'murica! Because I can. 2) military is switching to it and I wanted to be ahead of the curve when bulk U.S. ammo hits like it did for 5.56. 3) Gun grabbers never rest at trying to take guns and neither do I when it comes to buying or building them when I can. 4) the expansion in game seems to be better with the six eight within fifty yards and I need that for hunting on my property be it deer, coyotes or whatever.
 

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military is switching to it and I wanted to be ahead of the curve when bulk U.S. ammo hits like it did for 5.56.
From what I've read, if the military switches to a 6.8, it likely won't chamber in your gun. It will probably have some kind of plastic case rather than the brass 6.8 SPC case we on this forum use.
 

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First reason:'murica! Because I can. 2) military is switching to it and I wanted to be ahead of the curve when bulk U.S. ammo hits like it did for 5.56. 3) Gun grabbers never rest at trying to take guns and neither do I when it comes to buying or building them when I can. 4) the expansion in game seems to be better with the six eight within fifty yards and I need that for hunting on my property be it deer, coyotes or whatever.
The military has settled on a 6.8 caliber projectile, but they have NOT officially adopted the 6.8 SPC cartridge. And they are testing complete replacement's for the DI AR-15 series of rifles (yes, they are going with piston driven BCG's like every other combat rifle in the world, most likely the middle ground, a short stroke piston for which Sig seems to be the top contender right now).

The 6.8 SPC was more of a "proof of concept" to prove the point that an intermediate cartridge would better fill the role for medium and close range combat with maybe some limited longer range use with specialized loads. They have officially started a 27 month contract / field trials of various 6.8mm based cartridge and rifle designs including squad automatics, infantry rifles and heavy portable support guns using the .338 Norma Mag cartridge.

But your are correct, 6.8mm projectiles do have better terminal performance than 6.5mm projectiles at similar velocities. I meant no offense, I was just curious as to why build a 6.8 when you already had a 6.5.
 

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Discussion Starter #27
The military has settled on a 6.8 caliber projectile, but they have NOT officially adopted the 6.8 SPC cartridge. And they are testing complete replacement's for the DI AR-15 series of rifles (yes, they are going with piston driven BCG's like every other combat rifle in the world, most likely the middle ground, a short stroke piston for which Sig seems to be the top contender right now).

The 6.8 SPC was more of a "proof of concept" to prove the point that an intermediate cartridge would better fill the role for medium and close range combat with maybe some limited longer range use with specialized loads. They have officially started a 27 month contract / field trials of various 6.8mm based cartridge and rifle designs including squad automatics, infantry rifles and heavy portable support guns using the .338 Norma Mag cartridge.

But your are correct, 6.8mm projectiles do have better terminal performance than 6.5mm projectiles at similar velocities. I meant no offense, I was just curious as to why build a 6.8 when you already had a 6.5.
No problem hoss, thanks for the info
 

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I got my 6.8 spc from same place and it was stamped 6.8, no ll. I checked with seller who said all thier barrels were type ll chambers. I asked the same question on this forum as you did. I was told to put flat based bullet in fired case and put into chamber and carefully extract it. Measure the length and that would tell if it was a type ll chamber. I can't recall the length, but posted pictures of round in caliper, guys here said it was a type ll chamber. It shoots great. My best load hunting is Barnes ttsx 95 gr. 28 gr of aa2200.
 

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I got my 6.8 spc from same place and it was stamped 6.8, no ll. I checked with seller who said all thier barrels were type ll chambers. I asked the same question on this forum as you did. I was told to put flat based bullet in fired case and put into chamber and carefully extract it. Measure the length and that would tell if it was a type ll chamber. I can't recall the length, but posted pictures of round in caliper, guys here said it was a type ll chamber. It shoots great. My best load hunting is Barnes ttsx 95 gr. 28 gr of aa2200.
Awesome! Thank you hoss
 

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The military has settled on a 6.8 caliber projectile, but they have NOT officially adopted the 6.8 SPC cartridge. And they are testing complete replacement's for the DI AR-15 series of rifles (yes, they are going with piston driven BCG's like every other combat rifle in the world, most likely the middle ground, a short stroke piston for which Sig seems to be the top contender right now).

The 6.8 SPC was more of a "proof of concept" to prove the point that an intermediate cartridge would better fill the role for medium and close range combat with maybe some limited longer range use with specialized loads. They have officially started a 27 month contract / field trials of various 6.8mm based cartridge and rifle designs including squad automatics, infantry rifles and heavy portable support guns using the .338 Norma Mag cartridge.

But your are correct, 6.8mm projectiles do have better terminal performance than 6.5mm projectiles at similar velocities. I meant no offense, I was just curious as to why build a 6.8 when you already had a 6.5.
it wont be anything near 6.8 spc. They are trying to push the envelope. For a glance at the direction they are heading look no further than the .277 fury. SIG took what they have learned and been developing and made a civilian cartridge for it. If it lives up to the numbers, it gives you an idea of what the military is trying to do for the NGSW.
 

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.277 SIG Fury was designed for bolt guns, not semi-auto's. They wrote an article on that cartridge and specifically noted that the bolt lugs had to be "massive" to quote directly their term to handle the chamber pressures generated by that cartridge. It was intended achieve the performance of a much larger cartridge and out of a much shorter barrel to make a compact, lightweight long range rifle for military applications. i had thought the same thing until I started reading that article.

I suspect they will come up with a polymer case hybrid cartridge (to reduce weight) of similar size to 6.8 SPC that can push 2,700 to 3,000 fps out of projectiles in the 110gr to 130gr range for a typical assault rifle. Remember the more you jack up muzzle energy and projectile mass, the more recoil you have which is moving back towards 7.62x51...which they clearly don't want for an AR sized select fire infantry rifle.

Sure you can make a modern cartridge with similar or better performance than 7.62x51 with higher capacity and lower weight...but if it produces the same muzzle energy, it's also going to have substantial muzzle blast, substantial flash and recoil all of which which they feel are too high, especially on SBR's to be practical for infantry use. Hence why I suspect a refinement of the 6.8 SPC concept targeting slightly higher muzzle velocities to further enhance performance without being a 7.62x51 but with lower ammo weight than either.
 

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My personal opinion on the subject would be to take the existing 6.8 SPC cartridge, make a polymer hybrid variant of it and load it to the original military spec at 58,000 psi to hit 2700 fps on 110gr and then combine that with a 3R hammer forged chrome lined barrel in a SOCOM profile which is only 3oz heavier at the back than a "SCOUT" profile.

The better rifling design would allow them to push another 50 fps to 70 fps over what they achieved prior for further enhanced performance without any noticeable increase in recoil / muzzle flash, but hard chrome lining and hammer forging would provide better temperature resistance for full auto fire. Hard chrome will tolerate about 900F to 930F working temperature vs. nitrided steel at about 800F. Hammer forging provide rigidity when subjected to very high temperatures that a typical 4150 CMV barrel cannot provide.

Most modern military rifles use hammer forged barrels now days (SIG, HK, Izmash etc.). Basically what I'm proposing is a mass production version of ARPs 3R barrels but ruggedized for military use and using the original military loading specs or what we would consider "hand load performance" from a standard spec cartridge.
 

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My personal opinion on the subject would be to take the existing 6.8 SPC cartridge, make a polymer hybrid variant of it and load it to the original military spec at 58,000 psi to hit 2700 fps on 110gr and then combine that with a 3R hammer forged chrome lined barrel in a SOCOM profile which is only 3oz heavier at the back than a "SCOUT" profile.

The better rifling design would allow them to push another 50 fps to 70 fps over what they achieved prior for further enhanced performance without any noticeable increase in recoil / muzzle flash, but hard chrome lining and hammer forging would provide better temperature resistance for full auto fire. Hard chrome will tolerate about 900F to 930F working temperature vs. nitrided steel at about 800F. Hammer forging provide rigidity when subjected to very high temperatures that a typical 4150 CMV barrel cannot provide.

Most modern military rifles use hammer forged barrels now days (SIG, HK, Izmash etc.). Basically what I'm proposing is a mass production version of ARPs 3R barrels but ruggedized for military use and using the original military loading specs or what we would consider "hand load performance" from a standard spec cartridge.
That’s no where near the parameters listed by military. The fury with a 16” barrel hits 3000fps with a 140gr bullet.


.277 SIG Fury was designed for bolt guns, not semi-auto's. They wrote an article on that cartridge and specifically noted that the bolt lugs had to be "massive" to quote directly their term to handle the chamber pressures generated by that cartridge. It was intended achieve the performance of a much larger cartridge and out of a much shorter barrel to make a compact, lightweight long range rifle for military applications. i had thought the same thing until I started reading that article.

I suspect they will come up with a polymer case hybrid cartridge (to reduce weight) of similar size to 6.8 SPC that can push 2,700 to 3,000 fps out of projectiles in the 110gr to 130gr range for a typical assault rifle. Remember the more you jack up muzzle energy and projectile mass, the more recoil you have which is moving back towards 7.62x51...which they clearly don't want for an AR sized select fire infantry rifle.

Sure you can make a modern cartridge with similar or better performance than 7.62x51 with higher capacity and lower weight...but if it produces the same muzzle energy, it's also going to have substantial muzzle blast, substantial flash and recoil all of which which they feel are too high, especially on SBR's to be practical for infantry use. Hence why I suspect a refinement of the 6.8 SPC concept targeting slightly higher muzzle velocities to further enhance performance without being a 7.62x51 but with lower ammo weight than either.
The 277fury round is sigs round for the nexgen which is an auto. So it was indeed made for semi auto full auto and belt fed. May have to be built heavier but it was most definitely developed for auto use.

“The U.S. military wants a new belt-fed machine gun and put out a contract for one. SIG entered a belt-fed machine gun hoping to win the contract. The military specified the caliber of 6.8 or .277. Of course, the military wants the cartridge lighter and more powerful so SIG began developing the .277 Fury for that contract. SIG has been selected as one of the three finalists for the contract and will be going into full production with the .277 SIG Fury for the military.”

 

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The article only specifies that cartridge to be developed for squad automatics and bolt guns, not a lightweight infantry rifle to replace the AR-15 and it's variants (aka small frame). Perhaps they will put it into an infantry rifle as well at some point or a DMR platform, but I have my doubts about them squeezing that into a small framed select fire for typical infantry use.

It has a .308 head diameter and it's length significantly exceeds the ability of most small framed rifles, recoil, muzzle energy and ammo capacity are that of or exceed a .308 which the military was clear that was not acceptable for typical infantry use except on support type weapons (bolt action or squad autos like the 240 B).

This article provides greater clarity and context: .277 SIG Fury Demystified

The case head is the same diameter as .308 and 6.5mm Creedmoor cases. The case has a similar OAL to a .308.
Testing is still being conducted on barrel life, and most of the focus has been on the full-auto belt-fed machine gun barrels SIG is pitching to the military. They have done lots of testing on the bolt guns, too, but SIG isn’t ready to release numbers quite yet.
Current FN SAW 249 is chambered in the rather anemic and problematic 5.56 NATO variant of .223 AND it's heavier than comparable squad autos from other developed countries. The 240 Bravo is chambered in .308 and is even heavier yet. The .277 Fury fits the bill as higher performance replacement for .308 based squad auto's like the 240B (even heavier than the SAW 249) but with lower weight than either.

But a squad automatic allows one to use a heavy duty bolt head and lugs that an AR sized rifle would not. Ammunition capacity in an AR-15 sized rifle would be signfiicantly lower and recoil would increase to levels beyond a .308...can't get around the recoil energy from the exiting muzzle gasses and the mass of the BCG...

I think the requirements are quite different for squad autos and short barreled bolt guns for precision long range use than for typical infantry use and I have a hard time believing that they would build a low capacity infantry rifle based on .277 fury with very high recoil and increase the frame weight even more than an AR-15 when they are saying they need to either decrease it or keep it the same while improving performance.

I'm just saying that doesn't make much sense to assume the .277 Fury will be used as a replacement for 5.56. It does make perfect sense as an over match replacement for .308 or competing cartridges like 7.62x54R which has very similar performance to .308 / 7.62x51.
 

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The article only specifies that cartridge to be developed for squad automatics and bolt guns, not a lightweight infantry rifle to replace the AR-15 and it's variants (aka small frame). Perhaps they will put it into an infantry rifle as well at some point or a DMR platform, but I have my doubts about them squeezing that into a small framed select fire for typical infantry use.

It has a .308 head diameter and it's length significantly exceeds the ability of most small framed rifles, recoil, muzzle energy and ammo capacity are that of or exceed a .308 which the military was clear that was not acceptable for typical infantry use except on support type weapons (bolt action or squad autos like the 240 B).

This article provides greater clarity and context: .277 SIG Fury Demystified





Current FN SAW 249 is chambered in the rather anemic and problematic 5.56 NATO variant of .223 AND it's heavier than comparable squad autos from other developed countries. The 240 Bravo is chambered in .308 and is even heavier yet. The .277 Fury fits the bill as higher performance replacement for .308 based squad auto's like the 240B (even heavier than the SAW 249) but with lower weight than either.

But a squad automatic allows one to use a heavy duty bolt head and lugs that an AR sized rifle would not. Ammunition capacity in an AR-15 sized rifle would be signfiicantly lower and recoil would increase to levels beyond a .308...can't get around the recoil energy from the exiting muzzle gasses and the mass of the BCG...

I think the requirements are quite different for squad autos and short barreled bolt guns for precision long range use than for typical infantry use and I have a hard time believing that they would build a low capacity infantry rifle based on .277 fury with very high recoil and increase the frame weight even more than an AR-15 when they are saying they need to either decrease it or keep it the same while improving performance.

I'm just saying that doesn't make much sense to assume the .277 Fury will be used as a replacement for 5.56. It does make perfect sense as an over match replacement for .308 or competing cartridges like 7.62x54R which has very similar performance to .308 / 7.62x51.
But yet what you are saying flys in the face of the competition. Each entry of the 3 prototypes. ow is to replace the current infantry weapon.
 

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The article only specifies that cartridge to be developed for squad automatics and bolt guns, not a lightweight infantry rifle to replace the AR-15 and it's variants (aka small frame). Perhaps they will put it into an infantry rifle as well at some point or a DMR platform, but I have my doubts about them squeezing that into a small framed select fire for typical infantry use.

It has a .308 head diameter and it's length significantly exceeds the ability of most small framed rifles, recoil, muzzle energy and ammo capacity are that of or exceed a .308 which the military was clear that was not acceptable for typical infantry use except on support type weapons (bolt action or squad autos like the 240 B).

This article provides greater clarity and context: .277 SIG Fury Demystified





Current FN SAW 249 is chambered in the rather anemic and problematic 5.56 NATO variant of .223 AND it's heavier than comparable squad autos from other developed countries. The 240 Bravo is chambered in .308 and is even heavier yet. The .277 Fury fits the bill as higher performance replacement for .308 based squad auto's like the 240B (even heavier than the SAW 249) but with lower weight than either.

But a squad automatic allows one to use a heavy duty bolt head and lugs that an AR sized rifle would not. Ammunition capacity in an AR-15 sized rifle would be signfiicantly lower and recoil would increase to levels beyond a .308...can't get around the recoil energy from the exiting muzzle gasses and the mass of the BCG...

I think the requirements are quite different for squad autos and short barreled bolt guns for precision long range use than for typical infantry use and I have a hard time believing that they would build a low capacity infantry rifle based on .277 fury with very high recoil and increase the frame weight even more than an AR-15 when they are saying they need to either decrease it or keep it the same while improving performance.

I'm just saying that doesn't make much sense to assume the .277 Fury will be used as a replacement for 5.56. It does make perfect sense as an over match replacement for .308 or competing cartridges like 7.62x54R which has very similar performance to .308 / 7.62x51.
No one said it was going to be a small frame gun. However, if you actually look into the nexgen weapon system and the 3 contenders for it you will see that you are clearly wrong. the entire program is designed to find a replacement for current infantry weapon systems in 556. The army isnt trying to adapt M4's to work with a new round, they are looking at implementing an entire new weapon system. There are multiple threads on it here Military & Law Enforcement Discussion

Here is an article from G&A about the fury and the other next gen weapons and rounds.
NGSW Update: Push for the 6.8mm Continues

Or you can watch this video to get caught up quikly

 

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They seem to be going full circle in some ways because they clearly stated .308 was not suitable due to recoil, ammo capacity and muzzle flash in previous testing (2008 Roberts report)....SIG fury is even worse in recoil and flash, it also offers no gains in capacity over .308. The platform to support the cartridge in a semi-auto rifle is going to be heavier than an AR-15 frame.

It will be interesting to see how it all pans out. But that information you have provided along with some other articles / videos seem to indicate they are looking for a higher performance replacement cartridge for both DMR and Squad Automatic uses, not a direct replacement for 5.56, not at this point.

I suspect they still see the benefits of a higher capacity lightweight platform for close to medium ranges, but realized it's not suitable for extended ranges. There's a good reason squads used to have both smaller caliber weapons and at least one larger caliber weapon in a squad automatic or DMR rifle for suppression and longer range shooting.

You can outfit every man in the squad with that new Sig rifle using the .277 fury, but ammo capacity is going to suffer as will speed at close ranges. Mags are quite a bit longer as well, so it's not just capacity per a mag, it's how much you can carry on your rig.

Your always trading something off. Seems to me that history has shown us that the ability to mix and match for the mission is better than a "one size fits all" approach on average, even if two cartridges mean some members cannot share common ammo.

For example, units operating in the countryside of Afghanistan would have benefited significantly from using rifles chambered in the .277 SIG Fury where there was an emphasis on long range performance. But those same units would be at a disadvantage for urban warfare with the higher recoil, muzzle blast and significantly lower capacity of the .277 SIG Fury along with a heavier weapon that's slower to transition. Weight matters more than you think, especially when fatigue sets in.

6.8 SPC, 6.5 Grendel or 5.56 NATO are all better suited to close and medium ranges due to their low recoil, blast and higher capacity along with a lower weight platform.
 

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They seem to be going full circle in some ways because they clearly stated .308 was not suitable due to recoil, ammo capacity and muzzle flash in previous testing (2008 Roberts report)....SIG fury is even worse in recoil and flash, it also offers no gains in capacity over .308. The platform to support the cartridge in a semi-auto rifle is going to be heavier than an AR-15 frame.

It will be interesting to see how it all pans out. But that information you have provided along with some other articles / videos seem to indicate they are looking for a higher performance replacement cartridge for both DMR and Squad Automatic uses, not a direct replacement for 5.56, not at this point.

I suspect they still see the benefits of a higher capacity lightweight platform for close to medium ranges, but realized it's not suitable for extended ranges. There's a good reason squads used to have both smaller caliber weapons and at least one larger caliber weapon in a squad automatic or DMR rifle for suppression and longer range shooting.

You can outfit every man in the squad with that new Sig rifle using the .277 fury, but ammo capacity is going to suffer as will speed at close ranges. Mags are quite a bit longer as well, so it's not just capacity per a mag, it's how much you can carry on your rig.

Your always trading something off. Seems to me that history has shown us that the ability to mix and match for the mission is better than a "one size fits all" approach on average, even if two cartridges mean some members cannot share common ammo.

For example, units operating in the countryside of Afghanistan would have benefited significantly from using rifles chambered in the .277 SIG Fury where there was an emphasis on long range performance. But those same units would be at a disadvantage for urban warfare with the higher recoil, muzzle blast and significantly lower capacity of the .277 SIG Fury along with a heavier weapon that's slower to transition. Weight matters more than you think, especially when fatigue sets in.

6.8 SPC, 6.5 Grendel or 5.56 NATO are all better suited to close and medium ranges due to their low recoil, blast and higher capacity along with a lower weight platform.
It comes down to technology. As armor gets better, weapons have to as well. They are looking for more power. .277 for rifle and light machine gun, 6.5 Creedmore for Marksman, and .338 for medium / heavy machine gun. The Marksman rifle is already fielded. NGSW will pick the rifle / light MG. There are prototypes of .338, including the dillion minigun.
 
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