New Cartridge Developments and Implications for Dismounted Infantry Soldiers

[stanc]

Having someone drop a case of 7.62 ammo to you out of a chopper when you are carrying a 5.56, and vice versa really sucks.

Do you know of any cases where that actually happened?

[LRRPF52]

I think the AR15's compact magazine profile is one of its biggest benefits, when considering who will primarily be carrying service rifles or carbines. Just loading out your kit for an AR/M4 versus an AK or an FN/SR25/M14 will illustrate quickly the implications of the individual soldier's load on the entire logistics chain in not only weight, but space. Also add in the benefit of being able to assume a much lower prone position than any other 30rd mag-fed assault rifle, as well as the compactness of such a weapon in trenches, bunkers, thick vegetation, vehicles, and urban areas.

Regarding Military experience: I have only walked in one set of boots in my life at a time, and there is a vast collection of usable experience being shared by very few veterans, as many guys may peruse a forum, witness streams of immaturity spew from countless keyboard commandos, and turn away quickly, realizing their input might be disrespected or their honor questioned by some pre-pubescent anonymous adolescent without a clue.

This is why I highly value the Grendel forum for the gentlemanly conduct, respect, and open sharing of experience without ego or fanfare. By no means do I speak from a pulpit of my military experience trumping logic or the experience of others. I can only relate my input from the context that I experienced usage of military small arms in dismounted Infantry and Airborne units in a broad range of duty positions and deployments, as well as my understanding of the big picture of TO&E, logistics, training, and doctrine. I still am learning more about these subjects as I continue to work in the security industry, and claim no special status above the next contributor to a discussion.

Regarding AUTO mechanisms in the M4(A1): The benefits are in the SEMI mode of fire more than anything, while providing certain units the discretion of using controlled burst fire by the user in the AUTO mode. If you have ever had the opportunity to feel the trigger of an M16A2 or M4 with the 3-round burst mech, you will immediately notice the difference in pull weights as the burst counter cycles through its varying notches against the burst disconnector (there are two separate disconnectors in a burst trigger mechanism).

For the hard-chargers in the isolated COP's in Afghanistan, the Taliban methodically reconnoiter their crew-served weapons and Command & Control structures, and target those with PKM and RPG fire with the initiation of the deliberate attacks they are known for against such outposts. (Their training comes from a former 10th SFG E-7 gone officer, who later went to the CIA and oversaw the comprehensive UW program for the Mujahaideen in Pakistan during the Afghan-Soviet conflict in the 1980's, so they are practicing US small unit tactics in very disciplined and well-planned operations.)

This elimination of crew-served weapons placed a heavy burden on individual riflemen, and attests to the resolve that these units have shown under extended engagements that no real small arms are designed to handle without barrel changes. If a SAW was subjected to the rates of fire these guys used, you would go through several barrel changes if you ran the gun by the book for sustained, rapid, or emergency rates of fire. The fact that they have repelled the attacks without being successfully overrun speaks volumes to the warrior spirit of the units in question. The next question in my mind is how would they have fared if riflemen had been armed with M14's, AK's, or some other rifle. AK's will actually catch on fire when shot in extreme high-volume. M14's with a .625 pencil barrel blasting 7.62...high volume...ouch!

[bwaites]

OK, as a complete civilian newbie, can I point a couple of things out?

1) Multiple sources now report that SAAMI II chambering for the 6.8 SPC and the associated ammunition does not safely provide the upgrade that the SAAMI II advocates have promised. In fact Dr. Roberts has stated; "Every professional ballistics facility, including USG, foreign military, and Industry, that I am aware of that has tested 6.8 SPC vs. 6.8 SPCII using industry standard equipment has reported only a 1000-1500 psi change." This is confirmed by Johan Loubser at AA/Ramshot powders; "Yes we did exactly that and the difference was negligible as to be ignored ca 20-30Fps and <1000Psi.
I know there is a lot of claims out there regarding this. Some apply the effects of other calibers (such as the 223Rem) with completely different expansion ratios to the 6.8SPC.
The 6.8Spc is not sensitive to the slight changes in dimensions between the std and SPEC II."

So the SpecII chamber simply doesn't give the advantages proposed.

2) As I understand it, barrels are not the issue with sustained fire, gas tubes are. There is a very good video online demonstrating what happens to an AR with prolonged auto firing, and the gas tube is destroyed first, leaving the shooter with essentially a straight pull bolt action rifle.

Here is the Colt test, note the sound deadening used in the test tunnel in the background!: http://www.youtube.com/watch?v=Kzfm4pYhIyY

So I simply don't think that adding a better/heavier barrel will solve the issue, the weak link appears to be the gas tube, not the barrel. It may be true that repeated auto fire that approaches but does not cause gas tube failure might cause the barrel to become progressively damaged, decreasing accuracy, but any M4/M16 variant being used that way isn't going to be used as a long range sniper rifle anyways!

[stanc]

Multiple sources now report that SAAMI II chambering for the 6.8 SPC and the associated ammunition does not safely provide the upgrade that the SAAMI II advocates have promised. In fact Dr. Roberts has stated; "Every professional ballistics facility, including USG, foreign military, and Industry, that I am aware of that has tested 6.8 SPC vs. 6.8 SPCII using industry standard equipment has reported only a 1000-1500 psi change." This is confirmed by Johan Loubser at AA/Ramshot powders; "Yes we did exactly that and the difference was negligible as to be ignored ca 20-30Fps and <1000Psi."

So the SpecII chamber simply doesn't give the advantages proposed.

I'm not sure why you're discussing 6.8 SPC, but I must comment.

In the testing cited, they used only a special SAMMI test load, which makes the results much less than definitive or conclusive.

SPCII ammo (such as SSA Tactical, and Wilson Combat) has not been tested to see what would be the effect on pressure and velocity in SPCII vs SAAMI chambers.

[bwaites]

Stan, I mention the 6.8 because of this statement:

Very true. Even the underpowered loads from Remington deliver flatter trajectory than that of 7.62x39, and SPC II ammo provides a significant overmatch.

AND...even though a SAAMI cartridge was used in the Remington test, we aren't sure at all what was used in the AA/Ramshot testing. We do know that Dr. Roberts and Johan Loubser both say that no significant difference was found in using a SpecII chamber when it came to pressure differential, and Dr. Roberts says that he is aware of NO test which demonstrates that, in any testing facility, either commercial or military. It is beyond my belief that if that that extra velocity was actually there that no one would have been willing to load that ammo, especially considering they already had the setup to do so, IF that performance was available simply with a chamber change.

Even using hotter Spec II loads, do you believe it is remotely possible to achieve the results that the proponents are claiming? To achieve 200 FPS increases with 30 caliber bullets you have to go from standard to magnum cases, ie. from 30-06 velocities to .300 WinMag velocities. That means A LOT more powder, not the couple grains or faster powders that the 6.8 proponents propose is available simply with that chamber difference.

There is one exception, and it took Hornady quite some time to develop, and that is by developing a unique powder with specific properties, that appears to improve the performance of at least some cartridges to near magnum levels in standard cases. Even then, though, the promises are not so excessive as what the SPCII chamber proponents advocate are possible.

[stanc]

...even though a SAAMI cartridge was used in the Remington test, we aren't sure at all what was used in the AA/Ramshot testing. We do know that Dr. Roberts and Johan Loubser both say that no significant difference was found in using a SpecII chamber when it came to pressure differential, and Dr. Roberts says that he is aware of NO test which demonstrates that, in any testing facility, either commercial or military. It is beyond my belief that if that that extra velocity was actually there that no one would have been willing to load that ammo, especially considering they already had the setup to do so, IF that performance was available simply with a chamber change.

IMO, that's due mainly to concerns about liability. Although most 6.8 gun makers have switched to SPCII chambers and 1:11 twist rifling, there are many SAAMI-chambered, 1:9.5 twist guns still out there. I imagine the ammo makers fear that some dummy is bound to use SPCII ammo in a non-SPCII gun.

A contributing factor is that they're selling all the SAAMI-spec ammo they can produce, so they have no real profit motive to change.

And at least one manufacturer IS willing to make SPCII ammo. See below.

Even using hotter Spec II loads, do you believe it is remotely possible to achieve the results that the proponents are claiming?

Bill, I don't pay any heed to what handloaders are claiming, since there's no way for me to know if their loads are safe or not.

I strictly look at what's available in factory ammo. And in that, Wilson Combat is listing their SPCII loads with 110gr bullet @ 2700 fps from a 16" barrel. That's 150 fps faster than SAAMI loads from SSA, Hornady, etc, a substantially greater difference than the mere 20-30 fps noted by Loubser.

[bwaites]

Bill, I don't pay any heed to what handloaders are claiming, since there's no way for me to know if their loads are safe or not.

I strictly look at what's available in factory ammo. And in that, Wilson Combat is listing their SPCII loads with 110gr bullet @ 2700 fps from a 16" barrel. That's 150 fps faster than SAAMI loads from SSA, Hornady, etc, a substantially greater difference than the mere 20-30 fps noted by Loubser.

Duly noted. Of course ammunition manufacturers never inflate their numbers! (However, that said, their numbers for their .223 and .308 loads are consistent with other loadings, so I can certainly believe their numbers.)

Generally, when 3 witnesses, particularly 3 unrelated witnesses, give similar testimony, the court will rule in their favor. So far as I know, Dr. Roberts, Johan Loubser, and Mr. Silver from Remington have no contractual or other connections. When they say there is no significant difference in pressures between the two chambers, I would tend to believe them.

It will be interesting to see what 110 grain Wolf loads run when they are available for the Grendel.

[LRRPF52]

As I understand it, barrels are not the issue with sustained fire, gas tubes are. There is a very good video online demonstrating what happens to an AR with prolonged auto firing, and the gas tube is destroyed first, leaving the shooter with essentially a straight pull bolt action rifle.

So I simply don't think that adding a better/heavier barrel will solve the issue, the weak link appears to be the gas tube, not the barrel. It may be true that repeated auto fire that approaches but does not cause gas tube failure might cause the barrel to become progressively damaged, decreasing accuracy, but any M4/M16 variant being used that way isn't going to be used as a long range sniper rifle anyways!

I watched one of my Team Leaders melt a SAW barrel one night firing excessive string after string of rapid fire without changing barrels. Through NODs, you could clearly see the fore end of the barrel start to slowly bend downwards, ever so slightly. The SAW barrel has twice the chrome lining thickness of an M16, and is of machinegun-rated steel designed for full auto high volume. I do agree that heavier barrels are not the answer to addressing this limited problem with the M4 that was encountered by Joes in COPs set up for failure.

They're trying to address barrel influence by the RAS, dynamic tension on the handguard, and accessory mass influencing POI shift with a heavier barrel, when free-float is the real answer. Free-float also is the best thing you can do for heat dissipation, as SF and other SOCOM units have been doing with the RIS II.

When we talk about heat transfer in a weapon under unusually high volumes of fire, there will have to be a compromise somewhere else. AK's have failures in the op rod assembly, handguards catch fire, parts break, etc. Barrels melt and gas system parts will exceed design limitations somewhere in all the designs I know of. This is why the FAMAS and L85 can't reliably shoot standard M855 ammunition, and run on much lower-pressure cartridges. I think the French even use steel cases in the FAMAS since it will blow brass cases apart.

Op-rods on M14's break, gas pistons become fused in the block with excessive heating and cooling, and HK's will warp the stamped receivers under extreme high-volume, even in an MP5. Extreme heat is extreme heat at the end of the day. Combine that with extreme hot or cold climates, and the material expansion/contraction characteristics exceed design limitations quickly. If one were to attempt to solve this challenge by using an op-rod system, the problem just gets relocated and exposed to more environmental debris in the process, making failures under normal conditions more likely, a la HK416.

The one area I do see the Grendel offering an advantage in the heating challenges is that it operates at significantly lower pressures than 5.56 NATO, 6.8 SPC, and 7.62 NATO. An 85-100gr assault rifle load would also have comparable recoil characteristics to 5.56 NATO, as I have seen in my own 100gr Nosler Ballistic Tip loads with 29gr-31gr of TAC.

[stanc]

Generally, when 3 witnesses, particularly 3 unrelated witnesses, give similar testimony, the court will rule in their favor. So far as I know, Dr. Roberts, Johan Loubser, and Mr. Silver from Remington have no contractual or other connections. When they say there is no significant difference in pressures between the two chambers, I would tend to believe them.

I accept what they said as being true, insofar as it went. I don't feel like going back and rereading the two or three threads on the subject so as to link to verifying posts, but here is what I recall:

• Silvers said that to his knowledge, SPCII ammo had not been tested in the manner he described Loubser doing. That is, firing in a SAAMI chamber, then reaming the chamber to SPCII and firing again. Silvers agreed that testing SPCII ammo in this manner is something that really should be done in order to establish what differences there are in velocity and pressure.
  
  
• Roberts carefully avoided saying anything about what type of load(s) had been used in the pressure tests to which he alluded.

It will be interesting to see what 110 grain Wolf loads run when they are available for the Grendel.

Indeed.

[bwaites]

I accept what they said as being true, insofar as it went. I don't feel like going back and rereading the two or three threads on the subject so as to link to verifying posts, but here is what I recall:

• Silvers said that to his knowledge, SPCII ammo had not been tested in the manner he described Loubser doing. That is, firing in a SAAMI chamber, then reaming the chamber to SPCII and firing again. Silvers agreed that testing SPCII ammo in this manner is something that really should be done in order to establish what differences there are in velocity and pressure.
  
  
• Roberts carefully avoided saying anything about what type of load(s) had been used in the pressure tests to which he alluded.

Indeed.

I'm admittedly belaboring the point, but it doesn't REALLY matter what load you are using. If they saw less than a 30 FPS and 1500 PSI difference, in a SPCII chamber, than stepping up the load to anything short of a magnum load isn't going to bring that back to the results the SPCII adherents are claiming.

Lets say the SAAMI load produced 55,000 PSI in the standard chamber, and 53,500 PSI in the SPCII chamber. That means that just to MATCH the SAAMI load from a SAAMI chamber to an SPCII will require a load that would produce close to 56,500 PSI in a SAAMI chamber.

Then you want to increase velocity by 200 FPS or so? That's going to require a load that would run somewhere in the 62,000 or better range, comparing the 6.8 SAAMI and SPCII loads.

Not real likely that any manufacturer is going to put that one into production!

To get higher velocity, you need higher pressure, and to get pressure from a longer throat requires more powder, which is in short supply in these little cases!

[LRRPF52]

One thing I have noticed is the numerous references to 6.8 loads with the 85gr bullets at velocities at or over 2800 fps, and then using that as an example of the superiority of the 6.8 SPC to the Grendel, when I don't even recall anyone trying any 85gr projectiles in the Grendel yet, since 100gr is considered on the light end of the scale.

One advantage that some PDW builders using the SPC have related to me at SHOT is the unusually high velocities out of that cartridge from 7"-10" barrels, which is nice for a select few organizations out there in the diplomatic/VIP security arena, aside from the logistics and magazine capacity issues. I don't think anyone has even tried that with the Grendel yet, since most Grendel advocates are really pushing the downrange capabilities of the cartridge with longer barrels. I will say that before I loaded up some 100gr Nosler BT's, I had pretty much written the Grendel off as an assault rifle cartridge. After shooting those out of my A2 comp'd 16", a new bug started scratching me, but I'm still a well-convinced 5.56 Nazi when speaking strictly about an assault rifle or carbine for riflemen and special operations soldiers acting in an assaulter of dismounted shooter role, without any specialized tasks based on precision marksmanship.

We haven't even really looked at the potential of the Grendel in the CQB to 300m range as far as dedicated lightweight projectile loads go. I'll bet that the 100gr NBT out of the Grendel also makes a great 400m pill too. I really need an enhanced bolt from AR Performance if I'm to push the loads to where I think they can go for light projectile/high velocity in the Grendel. Harrison makes those bolts for the 6.8 and 7.62x39 already.

[stanc]

I'm admittedly belaboring the point, but it doesn't REALLY matter what load you are using. If they saw less than a 30 FPS and 1500 PSI difference, in a SPCII chamber, than stepping up the load to anything short of a magnum load isn't going to bring that back to the results the SPCII adherents are claiming.

If you mean what the handloaders are claiming, I agree that 200 fps increase while maintaining 55,000 psi isn't possible.

However, the 20-30 fps difference observed by Loubser doesn't correlate to the 80-100 fps gain listed for the SSA Tactical loads, and the 150 fps increase shown for Wilson Combat ammo. That can't be dismissed as inflated marketing numbers because it's too easy to verify by anyone with a chronograph.

[stanc]

One thing I have noticed is the numerous references to 6.8 loads with the 85gr bullets at velocities at or over 2800 fps, and then using that as an example of the superiority of the 6.8 SPC to the Grendel, when I don't even recall anyone trying any 85gr projectiles in the Grendel yet...

The greater popularity of 6.8 SPC has enabled development of a broader range of cartridge-specific bullets than for 6.5 Grendel.

However, even if 85gr .264" bullets were to become available for 6.5 Grendel, it still couldn't match muzzle velocities of 6.8 SPC. For one thing, there's a 5,000 psi difference in chamber pressure. For another, the larger "piston area" of .277" bullets lets them be pushed faster, even if chamber pressure were the same.

[LRRPF52]

Combined with significantly less bearing surface, and I can see how the short, fat .277 projectiles can be driven faster. It seems to me that after a few years of gaining pretty significant traction in the civilian sector, the 6.8 SPC doesn't stand a chance of being adopted by any military.

While the Grendel was slowly, ever so slowly gaining traction, it now seems to have really picked up in the civilian side. I commend Bill Alexander's commitment to maintaining rigid standards on chamber dimensions for Grendel-licensed barrels, which has most likely contributed to avoiding what happened with the SPC and the incorrect 80 degree shoulders in those Ko-Tonics barrels. That one Kaboom posted on barfcom was impressive, to say the least. A piece of the bolt carrier blew right through the mag well and wooden bench he was shooting off of, and completely fragmented the upper receiver. He had the SSA ammo with large rifle primers, and a Ko-Tonics pipe. I do believe Ko-Tonics made him happy after the incident, but examples like that illustrate the importance of standardization, QC in the industry as a whole, especially as something new starts to take off.

[stanc]

Combined with significantly less bearing surface, and I can see how the short, fat .277 projectiles can be driven faster. It seems to me that after a few years of gaining pretty significant traction in the civilian sector, the 6.8 SPC doesn't stand a chance of being adopted by any military.

Jordan reportedly plans to equip some of the Royal Guards with the 6.8 LWRC PSD, and acquired a license to make that model and a longer-barrel carbine version. Don't know why they'd want to go to the expense of setting up for local manufacture if they only wanted a few guns for VIP protection. OTOH, it's difficult to imagine them switching the entire military from 5.56 to 6.8 SPC. Time will tell.