Six Eight Debate

6.8x43mm SPC was developed by a group of SF soldiers to fill a need they perceived they had.

It failed in this limited role because the firearms industry made a couple of errors.  That's a debate for a different discussion.

The round did manage to capture the imagination of some dedicated hobbyists and they discovered the errors made and got the fixes adopted as the de facto standard for 6.8.

In fact, the new standard is so much improved it's caused a great many people to wonder if it should be considered to replace 5.56 now.

People have been wanting to replace 5.56 since about 1967, so this is not new.  What is new is that 6.8 seems so easy to transition to.  You don't even need to replace the entire gun!

Some history.  Just after The Great War The War to End All Wars World War One all of the involved armies looked hard at what guns they'd brought to the fight and if they'd been used in the manner for which they'd been designed.  Pretty much everyone agreed that they had not.  "What would be ideal for the war we'd just fought?" they all asked.  After killing a good many goats and pigs it was determined that a 7mm round with a max range around 600m would be about right.  The British were actually ahead of this curve having adopted .276 British for the Pattern 13 rifle just before the war.

"Oh shit there's a war on!" meant it was a bad plan to change over to .276 from .303 in 1914.  In 1919, there just wasn't any money to make any great changes, so .303 soldiered on until after WW2.  However, the studies led the US to adopt the .276 Pederson cartridge for the new M1 semiautomatic rifle.  10 rounds, clip loaded, gas operated!

"What about the mountains of .30-06 we have in warehouses?" asked Gen Douglas MacArthur?  Damn!  Well, 8 shots of .30-06 should do, no?  And it did.

Zee Germans were aware of these studies too, but were spending all their money on airplanes, tanks, ships and hiding that spending from the rest of the world.  They had a wonderful 7x35mm round from Switzerland they thought would be just perfect!  If only there were funding.  Well, maybe after the war...  They very nearly did adopt it during the war, in 1944.  That's when some irritating facts about tooling came to light and it became expedient to stay with a 7.92 caliber round; thus was born 7.92x33mm Kurz.

The Soviets were behind the curve, but aware of the studies.  When they decided that they'd like to take advantage of this knowledge, they hit the same tooling realities as the Germans and so their intermediate round ended up the same caliber as their old full-power round; so 7.62x39mm.

After the war yet another round of studying comes along.  AGAIN 7mm is identified as ideal and this time it's determined that riflemen very rarely shoot at anything beyond 400m so having a round that's lethal at 1,500m is unnecessary.  Everyone was impressed with the 7.92x33mm StG.44.  So much so that Fabrique National of Belgium designed the FAL round this round for NATO consideration.

The British remembered their research from 1913 and updated it with the 1945 material and came up with .280 British.  Then they adopted it and a rifle to shoot it.

But the US said, "Hey, those heavy thirty caliber rounds just won the war!  We shouldn't give up proven war winning capability just because nobody was utilizing it.  Plus they did fine in Korea too, so there!"  Enter 7.62x51mm...

Go ahead and keep your antiquated round say Belgium and Britain.  "Fine, pay for NATO without us!" says the US.  Thus the ideal round is tabled once again and 7.62x51mm remains our standard service rifle cartridge to this very day!

Wait... what?

There's another study creeping around the edges of the small arms design world.  Since it's mass times velocity squared, can't we substitute velocity for mass and get the same result?  Now we're in the world of Small Caliber High Velocity (SCHV).

This idea was embraced by a team at a little start-up splinter off of Fairchild Aircraft Corporation.  Armalite.  They downsized their AR10 into what's now known as the AR15 and pitched it at the Air Force, who were looking to replace their far from full-sized/power M1 carbines.

And Armalite made the sale!  They let out production to Colt and went around the world peddling their new whiz-bang space-age gun.  What emerges from the heady waters of Southeast Asian military sales/support is the wholesale adoption of the M16 over the "proven war winning standard" of the M14.  Enter 5.56x45mm M193.  The transition was neither smooth nor uncontroversial.  Reams have been written on it, but suffice it to say that 5.56 is a crown that rests heavy on the minds of many.

NATO was less than pleased by the US abandoning the standard NATO round.

The pesky Belgians enter into the fray again when NATO decides to adopt 5.56 as a standard.  They develop SS109 and L110 ball and tracer.  NATO put a requirement that any round that replaces 7.62x51mm NATO be able to punch a steel M1 helmet at 600m.  M193 couldn't.  SS109 has a steel portion to its core that does.  HUZZAH!  Everyone is happy for all time!

Except...

The US version of SS109 is M855 and it doesn't seem to do so well against unarmored people at much closer than 600m ranges, and this caused quite a stir in Mogadishu, Somalia.  Nevertheless, we stuck to our guns and called the situation there unique and not a good example of its typical performance.  After all, it seemed to work fine in Iraq.

Then there's the war on Tara (run Scarlet, RUN!).

The same sort of reports about M855 hitting, but not stopping the bad guys we saw in 1993 start happening again.  Then there are some reports that our guys can hit a long range, but the bullet is about useless out that far.

Several solutions to that have been put forward without changing chambering.  Mk 262 is a 77gr round based on a commercial hunting round.  Mk 318 is a 62gr bullet with a more conventional construction than M855.  Both seem to perform better on soft targets than M855 at all ranges.

Both the old M193 and newer M855 depend on the bullet flying to pieces when they hit.  A certain minimum velocity is required to cause that to happen.  It turns out that the impact angle of the bullet is critical too, and M855 is erratic about this.  Mk 262 and Mk 318 aren't and they fly apart at lower velocities which makes them more effective at longer ranges when the round has slowed.

6.8 is a solution to the erratic behavior of the M855.

The Army Marksmanship Unit helped develop the round and they dusted off the hoary old reams of data about the ideal round.  They wanted a round that fit in the M4 package with minimal changes.  They made lots of experimental cartridges.  They found that 7mm did the most damage and 6.5mm was most accurate and 6.8 the best compromise between.

So they finalized their design and Remington helped out a bunch and the wheels came off.

The commercial powder Remington used for the "issue" ammo was intolerant to the treatment it would receive in the hands of SF troops.  It lost velocity compared to virgin ammo and the round failed to perform as designed.  Failed experiment.

Remington got involved because they saw a lot of commercial appeal to a round that could fit in an AR with minimal changes.  Somewhere along the line, their submission to SAAMI contained an error in the chamber dimensions.  An error that raised the chamber pressures to dangerous levels.  To reduce the pressure, the amount of powder in the cartridge was reduced and thus velocity was reduced... another failure.

The AMU, SF and Remington all made the same error with regards to rifling.  A standard .277 barrel has 1:9 to 1:9.5 rifling because .270 Winchester has used this for decades.  It's less than ideal for the much lighter bullets required of the AR's magazine dimensions.

Enter the hobbyists!

The first thing that was attempted was to slow the rifling down.  It was immediately noticed that pressure signs on the brass were greatly reduced, so they experimented with adding more powder.  Velocities improved and pressures stayed in the safe range.  Increasing the leade back to where the initial order for the SF from Barrett had it also helped reduce pressure; so more velocity could be added.  This is now known as 6.8 SPC II.

In so many ways 6.8 is now far better than any 5.56 load.  Nearly twice the mass at 5/6 the velocity for a 115gr FMJ v M855.  Bigger hole even without fragmentation.  Reliable fragmentation at longer ranges with Sierra Matchking bullets.  Win, win; right?

Tactically, it's a huge win.  But amateurs study tactics, professionals study logistics.

A single round of 6.8x43mm is 44% heavier than M855.  A 25 round magazine is the same size and shape as a 30 round USGI magazine, but is 30% heavier.  A 30 round magazine doesn't fit existing pouches and is 70% heavier!  This extra mass must be transported and carried.

Pound per pound you can carry 5.38 (so five) 25-round 6.8 magazines or just four 30 round magazines where the 5.56 equipped soldier is packing seven 30 rounders.  Meaning that a 6.8 equipped troop has 120-125 rounds instead of 210.  That means it needs to be twice as good, but it's really only about 20% better.

If we make our troop carry 9 25-round mags to get the number of shots back up (225 rounds), we've got to take 4.7 pounds out of something else.  We're already crippling our grunts with the loads we make them haul.

The thing is, this is attainable.  It could be done.  Should we?

We have mountains of existing ammunition.  There's an eager market for surplus that would buy it at more than it cost to buy in the first place.

There's a huge training gorilla in the room.  6.8 hits the shoulder just a little harder and that affects follow-up shot speed.  6.8 really shines out past 300m as compared to 5.56 and we don't train to hit out there.  Both of these things require more shooting in training and more expenditure of ammo; which we're already reluctant to do with the cheaper 5.56.

5.56 costs less than 6.8; but the present price disparity might be because nobody is making millions of rounds of 6.8 in any loading.  Still it will cost more, regardless, because it uses more material.

The time to change over is when a unit is turning in its guns from wear, in peacetime.  The very time when budgets are tightest and there's the most number of unissued guns available at sunk cost.

As you can see, I like 6.8 and think it's viable.

But we don't need to change to it.

Rounds like the Mk 318 SOST are showing that you can eliminate the erratic behavior of M855 and keep 5.56.  And that's all that needs done.  Dropping the gravel-belly Cold War requirement that the round punch a helmet at ranges we call for artillery fire for is all that's needed to let SOST become standard.  If it weren't for the rebarelling issue, I'd say go back to M193 (oh and it has the same erratic behavior with regards to entry angle).

We've got to decide what we want our infantry rifle to do and then train our troops to do that with it.  Presently we've not made that decision and our training is not serving a defined end.