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New American 6.8mm rifle

U

Uncle Bob

SOC-14 1K
Well, it is mostly a M16, but the cartridge is a new 6.8mm SPC (.270) round. (AKA 6.8x43, 6.8 Remington)
http://64.177.53.248/ubb/Forum78/HTML/000512.html
(go to the "Terminal Effects" forum.)
7.5 g bullet at 808 m/s from a 47 cm barrel. Cartridge has nearly the same dimensions as the 5.56x45 (.223). You have to load 28 rds in a 30 rd magazine and each loaded magazine will weigh 100 g more than the same mag with 30 rd of M855 5.56).

The current US weapon is an M16 modified for special forces by Barrett (the .50cal rifle guys) but any 5.56mm Assault rifle can be rechambered to shoot it. Including the AR-18, G36, L85A2, AK-101, Galil, Stey AUG, etc, etc...

Look for the XM-8 to be issued in 6.8 SPC
 
Originally posted by Uncle Bob:
Well, it is mostly a M16, but the cartridge is a new 6.8mm SPC (.270) round. (AKA 6.8x43, 6.8 Remington)
http://64.177.53.248/ubb/Forum78/HTML/000512.html
(go to the "Terminal Effects" forum.)
7.5 g bullet at 808 m/s from a 47 cm barrel. Cartridge has nearly the same dimensions as the 5.56x45 (.223). You have to load 28 rds in a 30 rd magazine and each loaded magazine will weigh 100 g more than the same mag with 30 rd of M855 5.56).

The current US weapon is an M16 modified for special forces by Barrett (the .50cal rifle guys) but any 5.56mm Assault rifle can be rechambered to shoot it. Including the AR-18, G36, L85A2, AK-101, Galil, Stey AUG, etc, etc...

Look for the XM-8 to be issued in 6.8 SPC
Click to expand...
If the universe follows it's normal course this round is doomed. No 6-7mm round has made it into widespread service since before WWI, even though it's been proven again and again that this is the ballistically optimal size for a military round.
 
The .276 Pdersen was killed by the great depression.
The .280 British and 7mm intermediate were killed by a couple of fossils in the US Ordinance Corp.

But after forty years of the 5.56 they may be ready for a heavier round.
 
It would be interesting to see the SAW re-chambered in this round, it would become a light support weapon with more punch than the just sheer volume of fire it produces now.
 
The M249 Minimi could be re-chambered, but the Army has not been happy with the Minimi's durability.

There is a SAW version of the XM8 with a heavy 50 cm barrel, bipod, and 100 rd "C" magazine (double-snail design). In 6.8 that might be a 94 rd mag. This mag is based off the American Beta C magazine but the HK mags are reported to be much more reliable.
 
One of the attractions of the SAW concept is that it uses the same round as the infantryman's personal weapon. I can't see a rechambering being standard until the personal weapon gets up-calibred.
 
Originally posted by Uncle Bob:
The M249 Minimi could be re-chambered, but the Army has not been happy with the Minimi's durability.
Click to expand...
Interesting. I hadn't heard anything of that - can you point to anything on-line?

I do know that you shouldn't bother trying to use stanag magazines in it unless you're desparate. The belt mechanism is much more reliable.

Then again I'm a 7.62 bigot and would rather have to hump a M-240 and it's belts than a M-249 anyway. Of course either was a drastic improvement over the g*daweful M-60.

William
 
Sorry, William, no reference. I lost all my reference when my harddive crashed which is why I was vague. IIRC the Marines (with some of the oldest M249s in service) were particularly unhappy. I myself saw two different M249s jam during firefights on live video from OIF.
Of course even the Ma Deuce jammed in the Iraqi dust.

And Womble, the 6.8mm is a rfle catridge first. If the Army rechambers its M4s (Marine M16A4) they will want to rechamber the M249/SAW at the same time. If they wait for the M8 they can issue the M8 automatic rifle version to replace the M249.
 
I always thought the M249/Minimi was a compromise weapon that never really met the role laid out for it. The logisitcal reasons for chambering it in .223 while valid, left it with less poetntial than a squad support weapon should have. But then .223 left the M16 family of weapons under powered. I hope the idea of an increase in claiber takes hold, especially in the face of body armor becoming a more common sight on the battlefield.
 
The 6.8mm will probably have slightly worse performance againt armor than the 5.56mm. It has almost exactly the same energy/crossectional area as the 5.56mm M855 "greentip" and doesn't have the hardened steel insert.

But both will rip soft armor, neither will penetrate the ceramic armor of an "Interceptor" vest. To do that you need a sabot round or a 10 kilo rifle. Or the new 25mm version of the OICW with the HEAT round.
 
This is very interesting to me. I might have to get a 6.8mm upper for one of my Bushmasters when they're available. Especially if, as indicated, they can use the same 5.56mm magazines; I have a LOT of those.
 
Um, what's the difference between the 5.56 and 6.8 mm round, and why is the second better for the military?

Please, pretend that I'm the ignorant savage that I am, who knows nothing about ballistics.
 
Originally posted by Jame:
Um, what's the difference between the 5.56 and 6.8 mm round, and why is the second better for the military?

Please, pretend that I'm the ignorant savage that I am, who knows nothing about ballistics.
Click to expand...
It turns out that bullets in the 6.5-7mm range and of a weight useful for military small arms are ballistically very good, so you get excellent long-range performance 'for free', as it were. Also they're light enough to have little recoil, but long enough and heavy enough to have decent penetration and wounding potential.

Rounds in this size range were quite popular around 1900 but no major military power took any of them up (they all went for 7.5-8mm rounds), and when the US moved to a smaller calibre they chose 5.56mm, and everyone else pretty much followed suit.
 
Assault Rifles are a delicate compromise. If the cartridge is too powerful the rifle is too heavy (BAR) or uncontrolable (HK G3). A small, high velocity bullet doesn't penetrate very well (5.56x45, 5.45x39). Big, slow bullets (7.62x39) have a short range.

Details are sketchy, but the 6.8mm catridge seems to have a bigger powder charge than a 5.56x45mm (less taper?) and a bullet a little lighter and a good deal faster than the Russian 7.62x39mm

The Cd of this bullet seems to be lower than most 5.56, and no better than a Russion 7.62x39 (so it slows down pretty fast). But it will penetrate most barriers (wood, brick, sandbags, etc) better than the competitors. Terminal effects are a combination of bullet size, velocity, and construction, and it can be pretty complicated. Reportedly the 6.8mm does an awesome job of this, but there is hard data yet.

Me, I would have prefered a 6.35-6.5mm bore with a 7.5 g bullet but that wouldn't fit in a M16 magazine. An 6.8 mm package would be more efficient with a 8.5 g bullet and that may become available for auto rifles/light machine guns soon.
 
The biggest reason that U.S. forces used a .223 cal. round was the fact that once fired it did not fly in a straight line , but rather tumbled into it's target . Once the affected target was hit the tumbling nature of the round caused it to riccohet through out the targets body causing greater damage then a through and through round would be likel to do . The US military trains its troops to fire center of mass . While killing shots are less likely , the whole point of the .223 is to wound . If I shoot 1 OPFOR and wound him it will take 2 of his buddys to take him out of harms way as opposed to dropping 1 dead away at which point there is only 1 less in the firefight at that point.
 
Not exactly. The 5.56x45 is indended to cause rapid incapacitation with the least load and a superficial recognition of the Hague convention. Like other military spitzer-style (pointed) bullets, the 5.56 is directionally stable on the way to the target. Otherwise they would never hit the target, and milspec M193 ball can stay in a 30 cm circle at 300m.

Like all spitzers it is unstable inside the denser material of the target. Bullets yaw and tumble from 5-30 cm after penetration and typically end up about 30-40 degrees off the original line of flight. What makes the 5.56 M193)especially dangerous is that when it yaws 5-10 cm after contact it breaks up (at short range anyway), showering the interior with supersonic fragments that shred a region the size of a softball.

M995 AP does not fragment, M885 "green tip" often takes 10-15 cm before it yaws and fragments. The new Mk 263 yaws and fragments almost immediately for maximum effect.
 
I must admit that I'm stunned by Rupert's comment that no 6 to 7 mm round has been widely adopted since before World War I. This is completely untrue. I offer, as just the first in a long line of evidence, the AK-47. It is 7.62 mm and is, in my opinion, the most widely used assault rifle in the world. (Don't get me wrong, there are lots of M-16s in armories around the world, and its a fine weapon, especially in its later iterations, but for sheer omnipresence on every battlefield the AK-47 stands alone.)
 
Um... 7.62 mm is by definition greater than 6 to 7 mm. by over 0.62 mm to be exact.

I think the statement is specific to that range, typically occupied by 'deer slugs' (like the 0.270 in. Remington)

but I don't claim the level of expertise apparant in most of the posters to this topic.
 
In fact almost all military rifles from WW1 on were approx .30" or 7.62mm. It wasn't until the advent of the M-16 and AK-74 that the "standadard" diversified to 5.56mm (.22").

Still, the standards never included rifles of a calibre between 6.0mm and 7.0mm. Which implicit level of precision should have been obvious from the context of the thread.
 
Originally posted by womble:
In fact almost all military rifles from WW1 on were approx .30" or 7.62mm. It wasn't until the advent of the M-16 and AK-74 that the "standadard" diversified to 5.56mm (.22").

Still, the standards never included rifles of a calibre between 6.0mm and 7.0mm. Which implicit level of precision should have been obvious from the context of the thread.
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I should probably have been clearer, though - I did mean 6.0 - 7.0mm. This calibre range was quite popular with smaller powers prior to WWI, with rounds like the 6.5mm Swedish Mauser, the 7mm Mauser (7x57mm), and the 6.5mm Arisaka (thought that may be post-WWI) being fairly common. However after WWI there was a shift to the 7.5 - 8.0mm range that was common with the major powers, and all attempts at introducing 'mid-calibre' rounds failed for various reasons.
 
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