Army selects 6.8mm as the new common round... - Page 5

Bartholomew Roberts · October 14, 2018, 03:48 PM

Well, I think you nailed it rickyrick. SOCOM, Army, Marines, Navy... they’ve all looked at 6.8SPC and decided the juice wasn’t worth the squeeze. They’ve done about everything they can given the restraints of the AR15 action and magazine well.

There appears to be a strong desire to penetrate peer competitor body armor at 600m. I’m kind of skeptical that giving troops the equivalent of a .270 Magnum in a lightweight package with a short barrel is going to result in good things. Especially if you have a weapon and ammo that is too expensive to train with.

The Army stating this weapon is too expensive for them to arm everyone with it gives me pause.

davidsog · October 14, 2018, 05:27 PM

Just let em know they ask you!

marine6680 · October 14, 2018, 09:50 PM

In the Recoil article linked above...

They show a 6.5 caliber using the new bimetal case... That interests me more than a 6.8 does.

It appears to be similar in length to 5.56, but it may be a bit longer. The case looks like it has a bit more internal volume as well. Looks like what I have been talking about.

stagpanther · October 14, 2018, 11:32 PM

Quote:

It appears to be similar in length to 5.56, but it may be a bit longer. The case looks like it has a bit more internal volume as well. Looks like what I have been talking about.

Looks more like 2.8" xx308 to me--as do the weapons/magazine pics. The bimetal case design is what fascinates me--in the bigger scheme of things I can't see how a .0000x ounce per cartridge saving adding up to anything significant to the soldier lugging the ammo can around is going to notice. Case head is often what flows/fails when the pressures ramp up, so I'm thinking we might (?) be looking at a cartridge design intended to run at significantly higher pressures.

marine6680 · October 15, 2018, 03:04 AM

You think? It looks smaller than a 308 based case to me. I could just be seeing it wrong on my phone screen.

20% weight difference is not insignificant, if an ammo load weighed 5lb, it would be 4lb at 20% less weight.

Polymer hybrid designs are starting to be viable as well. I think they save a little more. My only concern would be the case holding up when loaded for a long time. Mag fed shotguns have the issue of deformed hulls when left loaded for a while. But shotgun hulls are fairly weak though.

When it comes to making good ordinance and weapon decisions... The US military has a spotty record at best.

The M14 was a flop of a rifle, that came about because the ones in charge didn't want to listen to the ones that did the studies and research, nor the Brits who had picked up on the idea of intermediate calibers very quickly after WWII.

The higher ups who hated the idea of the M16 deliberately worked to sabotage the rifle, including messing with the design, not training on proper care and cleaning, and knowingly sending out known bad ammo to the field... Things they knew would cause casualties.

You want a good rifle and ammo combination... Ask those outside the military. So long as they don't have any vested interest in the weapons and ammo the military may adopt... And they have a good grasp of ballistics and bullet design.

M855a1 works well from the reports coming in about it... But it is hard on the rifles. So a change in caliber does make sense. But you have to take a realistic look at the needs and realities. I still don't think a single caliber will cut it... You need the general issue to be very effective inside 300yds, but still useful out to 500yds give or take. For effective use past 500yds, you would need something else. And yet one more for use in an SBR, that is effective inside 100-150yds. I just don't think a signle round can do all those well. Maybe you could have a single caliber but different variations, and it would work.

But as was said... No matter what you choose, the military is limited on bullet design. So civilian ammo will still likely be better.

stagpanther · October 15, 2018, 06:11 AM

Take a look at the article linking to Sig's submissions. I think it's easy to see that's not a 2.26 cartridge. Take a closer look at the weapons--it's also easy to see the magazine is also not a short 2.3 +/-.

What's also interesting to see is that the carbine weapons are buffer-less designs by virtue of the lack of buffer tubes and folding stocks. Pretty obvious it's a gas-piston system with some sort of carrier system for absorbing recoil all within the upper receiver--might even be a side-charger. I'm going to guess there's some kind of facility for quick and easy barrel swap-out as well.

Looks like they also are going with some kind of special coating on the projectile--I'm guessing they found a coating that reduces friction and increases velocity while reducing bore fouling. Or maybe it's just a coating to hide the new super-secret frickin-sharks-with-lasers projectile technology?

stagpanther · October 15, 2018, 06:32 AM

There's not only how well the system works--but how well it fails. I see a potential high pressure multiple-part cartridge design and my first reaction is "rut-rooh." Tiny little headspace or jam issues have a nasty way of potentially rapidly increasing pressure. Having blown up a couple of rifles myself--I'd be interested in what happens in a failure mode. Having troops in the field testing portable IED's isn't very fair way to test that.

Bartholomew Roberts · October 15, 2018, 11:39 AM

Speaking of pressure, even if they are using a low-friction coating on the projectile, throat erosion on that has got to be tremendous. Some type of new surface treatment that is extremely resistant to heat checking?

Jim Watson · October 15, 2018, 04:43 PM

The USMC tried real Teflon coating on bullets.
Some promising early observations could not be reproduced, so they gave up on it.

marine6680 · October 15, 2018, 04:57 PM

I was looking at the recoil article that Bart linked to.

It had a cartridge that was labeled using a lable maker, as 6.5 on it's side. I do not recall seeing that in the original links. With those being obviously larger than typical 5.56 dimensions.

Failure can be factored in... A case rupture is bad all around, exactly where it fails is less of a concern in the end.

Lots of testing will be required to know if the new type of case works long term.

Barrel wear can be controlled with good design of the caliber. The ratio between the case diameter and neck diameter plays a role, as well as other factors.

davidsog · October 16, 2018, 10:06 AM

SIG actually states their 6.8mm is based on existing 7.62mm casing. SOCOM’s uppers are going to piston instead of gas impingement.

Has anyone of importance got a hold of you guys for your input yet? Seems ashame not to...

marine6680 · October 16, 2018, 01:31 PM

You have been consistently wrong... Yet remain smug.

Dunning-Kruger would have a field day with you.

davidsog · October 16, 2018, 01:43 PM

Exactly what do you think I have been wrong on?

5.56mm is not very good for stopping power for home defense and no wonder bullet exist to fix it?

Measured engineering study agrees with my battlefield experience.

Or are you unable to see the fact the Army’s search for a replacement to fix that shortcoming began with 6.8 mm and ended with the same?

I want to know why not one single post of mine has attacked anyone personally but that is all you seem to be capable. Intellectually that is a sign you have nothing factual to defend a position.

davidsog · October 16, 2018, 02:09 PM

By some folks logic.....

The 1903 Flyer has nothing to do with Space Shuttle.

Sharkbite · October 16, 2018, 02:36 PM

Quote:

Exactly what do you think I have been wrong on?

5.56mm is not very good for stopping power for home defense and no wonder bullet exist to fix it?

Yep, thats a good start.

Again, there are NUMEROUS loading avail to civilians and LE that the Military cannot/will not use that are MUCH better at stopping people in HD/SD scenarios then the current Mil loadings.

stagpanther · October 16, 2018, 02:39 PM

David's right to the extent my reflections are just an armchair quarterback's--but then that's part of the reason we have this forum--else he can hang out on a "for operators only" forum if the "who swings the biggest pair in the jungle" is what he really wants to establish. It's for that reason I make it clear that I'm not an expert with any real experience in every post I make.

marine6680 · October 16, 2018, 04:25 PM

Haha... Seriously?

You have been very snide to others quite often in your time posting on this forum.

Don't try to throw out your falacy fallacy on me, trying to claim my irritation is an indication of error in my judgement...

Myself and several others have provided you ample data and information. We have argued this with you over several threads on this forum. Not only from those of us, like myself who have a decent academic knowledge of the subject, but even those with direct experience of the effects of and/or testing done on LE and Civilian ammo. (I myself have never claimed expertise, only a decent overall understanding, with a background studying engineering and physics, and a passion for learning about firearms and ballistics.)

I have just simply reached a limit on dealing with your willful ignorance. (It borders on that of flat Earth nuts)

Your inability to understand the actual facts, and the vast amounts of evidence that counters your point of view has grown tiresome. I am just simply disinclined to continue being cordial in my interactions with you. I can only repeat myself so many times before I grow too weary for civility.

2damnold4this · October 16, 2018, 04:40 PM

Will the Army be replacing the millions XM8 rifles it purchased at great expense just a few years ago? : )

Sharkbite · October 16, 2018, 06:04 PM

Quote:

I have just simply reached a limit on dealing with your willful ignorance. (It borders on that of flat Earth nuts)

Goes to show the mentality of some of the “top tier” guys.

rickyrick · October 16, 2018, 06:25 PM

The fact that the 5.56mm (in some form) is still in use by the military after all these years is a testament to its effectiveness. If the 5.56 had been a failure in the 60s it would have been replaced in the 1970s for sure. The army is pretty good about replacing equipment that isn’t performing: trucks, tanks, nbc masks, uniforms, wrenches and so forth. Heck the hmmwv has almost came and went in the time the 5.56mm has been in service. It’s pure BS to think that the military is keeping a sub-par cartridge out of spite or any other nefarious reason... fact is, nothing has been able to replace the 5.56mm satisfactorily yet.

I’m not the smartest, and sometimes I become a troll... but there’s at least one person here that needs to brush up on middle-school physics and a touch of biology.

Nothing wrong with trying to find something better. I’m sure eventually something will come along to replace the 5.56 and I think something between 6-7mm in a longer cartridge might do the trick...

ed308 · October 17, 2018, 08:58 AM

Exactly. Very deadly at close range too.

I'm certainly no expert. But the Army figured out the 5.56 doesn't have the mass the defeat the body armor of enemy combatants. They decided the 7.62 has too much mass. So they've picked a bullet in between the two by settling on 6.8. That surprised me with all the rage of the 6.5 gets. But they've made their choice.

stagpanther · October 17, 2018, 09:10 AM

Quote:

So they've picked a bullet in between the two by settling on 6.8. That surprised me with all the rage of the 6.5 gets. But they've made their choice.

Not really--the .277 lies between the .264 and .284--both calibers that have a very long record of proven intermediate and intermediate-long range performance with ideal BC and SD characteristics. The .277 has come a long way and now has a wide selection from shorter flat base to long high SD/BC bullets. Makes perfect sense to me.

Bartholomew Roberts · October 17, 2018, 09:25 AM

Yeah, 6.5-7mm is pretty much the ballistic sweet spot. 6.8 is kind of splitting the baby. I mean, how long has .270 WIN been around now?

As for CQB performance, they are saying they’ve somehow achieved a revolutionary increase in velocity - as in this will launch a 125gr 6.8 bullet at 3,500fps. That’s twice the mass of M855A1 and traveling about 450fps faster to boot.

Apparently, they are also going to be relying on a new integrated optic system to keep qualification scores from plummeting across the board: http://soldiersystems.net/2018/10/15...omment-1097021

So, if the cartridge is 20% less weight and you can save another 5% by a smaller bullet, polymer mags, etc. You are looking at decreasing the basic load to about 175 rounds (using 7.62x51 weights as a rough basis for calculation since it uses that action). You are also going to be creating a ton of heat it would seem - with less barrel mass to act as a heat sink. I wonder what they are going to do about that?

**Mike Irwin** · October 17, 2018, 09:28 AM

Personally, my bet is that the US will still be using the 5.56 as its primary military round in 2050.

marine6680 · October 17, 2018, 09:44 AM

Unless caseless or some other revolutionary advancement in ammo is developed before then... Probably so.

The reason I think 6.5 is a better choice over 6.8 is a few things.

You want more mass, you want to keep velocities where they are now or higher, you want to minimize any weight increase and recoil increase. You want it to be effective out to intermediate ranges with a barrel around 16in give or take.

I think to get 6.8 to be efficient ballistically, you need projectiles that are over 100grs, for the larger width to diameter ratio that seems to make for good BC.

Heavier bullets mean more powder to keep velocities high... More recoil, and overall a much larger jump in total ammo weight.

I think the job can be done with projectile weight around 85-90gr... So a smaller caliber can get an efficient bullet design with lower weight. Then using projectile design like the m855a1 can provide good terminal effects and decent armor defeating.

October 15, 2018, 06:11 AM	#106
stagpanther Senior Member Join Date: March 2, 2014 Posts: 11,784	Take a look at the article linking to Sig's submissions. I think it's easy to see that's not a 2.26 cartridge. Take a closer look at the weapons--it's also easy to see the magazine is also not a short 2.3 +/-. What's also interesting to see is that the carbine weapons are buffer-less designs by virtue of the lack of buffer tubes and folding stocks. Pretty obvious it's a gas-piston system with some sort of carrier system for absorbing recoil all within the upper receiver--might even be a side-charger. I'm going to guess there's some kind of facility for quick and easy barrel swap-out as well. Looks like they also are going with some kind of special coating on the projectile--I'm guessing they found a coating that reduces friction and increases velocity while reducing bore fouling. Or maybe it's just a coating to hide the new super-secret frickin-sharks-with-lasers projectile technology? __________________ "Everyone speaks gun."--Robert O'Neill *I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!* Last edited by stagpanther; October 15, 2018 at 06:19 AM.

October 15, 2018, 06:32 AM	#107
stagpanther Senior Member Join Date: March 2, 2014 Posts: 11,784	There's not only how well the system works--but how well it fails. I see a potential high pressure multiple-part cartridge design and my first reaction is "rut-rooh." Tiny little headspace or jam issues have a nasty way of potentially rapidly increasing pressure. Having blown up a couple of rifles myself--I'd be interested in what happens in a failure mode. Having troops in the field testing portable IED's isn't very fair way to test that. __________________ "Everyone speaks gun."--Robert O'Neill *I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!* Last edited by stagpanther; October 15, 2018 at 06:37 AM.

October 16, 2018, 01:43 PM	#113
davidsog Senior Member Join Date: January 13, 2018 Posts: 1,326	Exactly what do you think I have been wrong on? 5.56mm is not very good for stopping power for home defense and no wonder bullet exist to fix it? Measured engineering study agrees with my battlefield experience. Or are you unable to see the fact the Army’s search for a replacement to fix that shortcoming began with 6.8 mm and ended with the same? I want to know why not one single post of mine has attacked anyone personally but that is all you seem to be capable. Intellectually that is a sign you have nothing factual to defend a position. Last edited by davidsog; October 16, 2018 at 01:48 PM.

October 16, 2018, 02:39 PM	#116
stagpanther Senior Member Join Date: March 2, 2014 Posts: 11,784	David's right to the extent my reflections are just an armchair quarterback's--but then that's part of the reason we have this forum--else he can hang out on a "for operators only" forum if the "who swings the biggest pair in the jungle" is what he really wants to establish. It's for that reason I make it clear that I'm not an expert with any real experience in every post I make. __________________ "Everyone speaks gun."--Robert O'Neill *I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!*

October 17, 2018, 09:25 AM	#123
Bartholomew Roberts member Join Date: June 12, 2000 Location: Texas and Oklahoma area Posts: 8,462	Yeah, 6.5-7mm is pretty much the ballistic sweet spot. 6.8 is kind of splitting the baby. I mean, how long has .270 WIN been around now? As for CQB performance, they are saying they’ve somehow achieved a revolutionary increase in velocity - as in this will launch a 125gr 6.8 bullet at 3,500fps. That’s twice the mass of M855A1 and traveling about 450fps faster to boot. Apparently, they are also going to be relying on a new integrated optic system to keep qualification scores from plummeting across the board: http://soldiersystems.net/2018/10/15...omment-1097021 So, if the cartridge is 20% less weight and you can save another 5% by a smaller bullet, polymer mags, etc. You are looking at decreasing the basic load to about 175 rounds (using 7.62x51 weights as a rough basis for calculation since it uses that action). You are also going to be creating a ton of heat it would seem - with less barrel mass to act as a heat sink. I wonder what they are going to do about that? Last edited by Bartholomew Roberts; October 17, 2018 at 09:30 AM.

October 14, 2018, 03:48 PM	#101
Bartholomew Roberts member Join Date: June 12, 2000 Location: Texas and Oklahoma area Posts: 8,462	Well, I think you nailed it rickyrick. SOCOM, Army, Marines, Navy... they’ve all looked at 6.8SPC and decided the juice wasn’t worth the squeeze. They’ve done about everything they can given the restraints of the AR15 action and magazine well. There appears to be a strong desire to penetrate peer competitor body armor at 600m. I’m kind of skeptical that giving troops the equivalent of a .270 Magnum in a lightweight package with a short barrel is going to result in good things. Especially if you have a weapon and ammo that is too expensive to train with. The Army stating this weapon is too expensive for them to arm everyone with it gives me pause.

October 14, 2018, 05:27 PM	#102
davidsog Senior Member Join Date: January 13, 2018 Posts: 1,326	Just let em know they ask you!

October 14, 2018, 09:50 PM	#103
marine6680 Senior Member Join Date: July 24, 2012 Location: Parker, CO Posts: 4,594	In the Recoil article linked above... They show a 6.5 caliber using the new bimetal case... That interests me more than a 6.8 does. It appears to be similar in length to 5.56, but it may be a bit longer. The case looks like it has a bit more internal volume as well. Looks like what I have been talking about.

October 15, 2018, 03:04 AM	#105
marine6680 Senior Member Join Date: July 24, 2012 Location: Parker, CO Posts: 4,594	You think? It looks smaller than a 308 based case to me. I could just be seeing it wrong on my phone screen. 20% weight difference is not insignificant, if an ammo load weighed 5lb, it would be 4lb at 20% less weight. Polymer hybrid designs are starting to be viable as well. I think they save a little more. My only concern would be the case holding up when loaded for a long time. Mag fed shotguns have the issue of deformed hulls when left loaded for a while. But shotgun hulls are fairly weak though. When it comes to making good ordinance and weapon decisions... The US military has a spotty record at best. The M14 was a flop of a rifle, that came about because the ones in charge didn't want to listen to the ones that did the studies and research, nor the Brits who had picked up on the idea of intermediate calibers very quickly after WWII. The higher ups who hated the idea of the M16 deliberately worked to sabotage the rifle, including messing with the design, not training on proper care and cleaning, and knowingly sending out known bad ammo to the field... Things they knew would cause casualties. You want a good rifle and ammo combination... Ask those outside the military. So long as they don't have any vested interest in the weapons and ammo the military may adopt... And they have a good grasp of ballistics and bullet design. M855a1 works well from the reports coming in about it... But it is hard on the rifles. So a change in caliber does make sense. But you have to take a realistic look at the needs and realities. I still don't think a single caliber will cut it... You need the general issue to be very effective inside 300yds, but still useful out to 500yds give or take. For effective use past 500yds, you would need something else. And yet one more for use in an SBR, that is effective inside 100-150yds. I just don't think a signle round can do all those well. Maybe you could have a single caliber but different variations, and it would work. But as was said... No matter what you choose, the military is limited on bullet design. So civilian ammo will still likely be better.

October 15, 2018, 11:39 AM	#108
Bartholomew Roberts member Join Date: June 12, 2000 Location: Texas and Oklahoma area Posts: 8,462	Speaking of pressure, even if they are using a low-friction coating on the projectile, throat erosion on that has got to be tremendous. Some type of new surface treatment that is extremely resistant to heat checking?

October 15, 2018, 04:43 PM	#109
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,541	The USMC tried real Teflon coating on bullets. Some promising early observations could not be reproduced, so they gave up on it.

October 15, 2018, 04:57 PM	#110
marine6680 Senior Member Join Date: July 24, 2012 Location: Parker, CO Posts: 4,594	I was looking at the recoil article that Bart linked to. It had a cartridge that was labeled using a lable maker, as 6.5 on it's side. I do not recall seeing that in the original links. With those being obviously larger than typical 5.56 dimensions. Failure can be factored in... A case rupture is bad all around, exactly where it fails is less of a concern in the end. Lots of testing will be required to know if the new type of case works long term. Barrel wear can be controlled with good design of the caliber. The ratio between the case diameter and neck diameter plays a role, as well as other factors.

October 16, 2018, 10:06 AM	#111
davidsog Senior Member Join Date: January 13, 2018 Posts: 1,326	SIG actually states their 6.8mm is based on existing 7.62mm casing. SOCOM’s uppers are going to piston instead of gas impingement. Has anyone of importance got a hold of you guys for your input yet? Seems ashame not to...

October 16, 2018, 01:31 PM	#112
marine6680 Senior Member Join Date: July 24, 2012 Location: Parker, CO Posts: 4,594	You have been consistently wrong... Yet remain smug. Dunning-Kruger would have a field day with you.

October 16, 2018, 02:09 PM	#114
davidsog Senior Member Join Date: January 13, 2018 Posts: 1,326	By some folks logic..... The 1903 Flyer has nothing to do with Space Shuttle.

October 16, 2018, 04:25 PM	#117
marine6680 Senior Member Join Date: July 24, 2012 Location: Parker, CO Posts: 4,594	Haha... Seriously? You have been very snide to others quite often in your time posting on this forum. Don't try to throw out your falacy fallacy on me, trying to claim my irritation is an indication of error in my judgement... Myself and several others have provided you ample data and information. We have argued this with you over several threads on this forum. Not only from those of us, like myself who have a decent academic knowledge of the subject, but even those with direct experience of the effects of and/or testing done on LE and Civilian ammo. (I myself have never claimed expertise, only a decent overall understanding, with a background studying engineering and physics, and a passion for learning about firearms and ballistics.) I have just simply reached a limit on dealing with your willful ignorance. (It borders on that of flat Earth nuts) Your inability to understand the actual facts, and the vast amounts of evidence that counters your point of view has grown tiresome. I am just simply disinclined to continue being cordial in my interactions with you. I can only repeat myself so many times before I grow too weary for civility.

October 16, 2018, 04:40 PM	#118
2damnold4this Senior Member Join Date: August 12, 2009 Location: Athens, Georgia Posts: 2,526	Will the Army be replacing the millions XM8 rifles it purchased at great expense just a few years ago? : )

October 16, 2018, 06:25 PM	#120
rickyrick Senior Member Join Date: March 15, 2010 Posts: 8,236	The fact that the 5.56mm (in some form) is still in use by the military after all these years is a testament to its effectiveness. If the 5.56 had been a failure in the 60s it would have been replaced in the 1970s for sure. The army is pretty good about replacing equipment that isn’t performing: trucks, tanks, nbc masks, uniforms, wrenches and so forth. Heck the hmmwv has almost came and went in the time the 5.56mm has been in service. It’s pure BS to think that the military is keeping a sub-par cartridge out of spite or any other nefarious reason... fact is, nothing has been able to replace the 5.56mm satisfactorily yet. I’m not the smartest, and sometimes I become a troll... but there’s at least one person here that needs to brush up on middle-school physics and a touch of biology. Nothing wrong with trying to find something better. I’m sure eventually something will come along to replace the 5.56 and I think something between 6-7mm in a longer cartridge might do the trick...

October 17, 2018, 08:58 AM	#121
ed308 Senior Member Join Date: November 5, 2016 Location: DFW, TX Posts: 1,147	Exactly. Very deadly at close range too. I'm certainly no expert. But the Army figured out the 5.56 doesn't have the mass the defeat the body armor of enemy combatants. They decided the 7.62 has too much mass. So they've picked a bullet in between the two by settling on 6.8. That surprised me with all the rage of the 6.5 gets. But they've made their choice.

October 17, 2018, 09:28 AM	#124
Mike Irwin Staff Join Date: April 13, 2000 Location: Northern Virginia Posts: 41,389	Personally, my bet is that the US will still be using the 5.56 as its primary military round in 2050. __________________ "The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza Baby Jesus cries when the fat redneck doesn't have military-grade firepower.

October 17, 2018, 09:44 AM	#125
marine6680 Senior Member Join Date: July 24, 2012 Location: Parker, CO Posts: 4,594	Unless caseless or some other revolutionary advancement in ammo is developed before then... Probably so. The reason I think 6.5 is a better choice over 6.8 is a few things. You want more mass, you want to keep velocities where they are now or higher, you want to minimize any weight increase and recoil increase. You want it to be effective out to intermediate ranges with a barrel around 16in give or take. I think to get 6.8 to be efficient ballistically, you need projectiles that are over 100grs, for the larger width to diameter ratio that seems to make for good BC. Heavier bullets mean more powder to keep velocities high... More recoil, and overall a much larger jump in total ammo weight. I think the job can be done with projectile weight around 85-90gr... So a smaller caliber can get an efficient bullet design with lower weight. Then using projectile design like the m855a1 can provide good terminal effects and decent armor defeating.