Although it wasn’t part of the formal new product reveals of SIG NEXT, the defense team showed me a 10″ upper for the US Army’s M7 Next Gen Rifle.
Seen to the right is the standard 13″ barrel length version which is currently under contract.
While the model I fired was equipped with the folding stock knuckle, they told me they have demonstrated a carbine version of the M7 which has a standard AR-style collapsible stock, eliminating the folding mechanism. Combined with a 10″ barrel, the weight is 7.3 lbs (without suppressor). By contrast, the M27 weighs 7.9 lbs and the standard M7 weighs 8.38 lbs.
With the shorter barrel length is a slight drop in velocity, to 2850 fps from ~3000 fps for the current M7.
I was hoping you might be able to get some info on the HYP. A DI 716 built to handle the hybrid ammo that was announced but not on the website yet.
It’s coming
That 6.8mm round is smoking to be getting 2800+ fps out of a 10″ barrel. Understanding the M7 does what Big Army asked it to do this is something that should be considered.
Shaving ounces from the soldier’s load is always desirable and even the modest shortening of the barrel will enhance weapon’s handling by bringing the center of balance more towards the shooter.
SiG XM-7 And 6.8x51mm Problems, Not In Order Of Importance:
1) High Pressures Equal Weapon Wear And Barrel Erosion: The requirement to generate armor piercing energies from a 13” barrel with only 10.5 inches of rifling resulted in a cartridge of >80,000 PSI. Gunpowder per GD St. Marks burns at 3,000-3,100 degrees F in atmosphere, over 4,200 degrees F at 55,000 PSI and an unknown temperature greater than 4,750 degrees F at over 80,000 PSI. Unfortunately, Steel melts at under 2,800F and Chrome vaporizes at 3,400F…so “throated” barrel accuracy life will be “short”, perhaps under 3,000 rounds even fired semi-automatic at low rates.
2) Maximum Pressures Are Generally Less Accurate: Ordinarily you wouldn’t pick as your first choice a 13” carbine which needs historically high pressure to hit much less penetrate an enemy armor plate at 600 yards, but if somehow you did…accuracy is extremely important, because: “The First Rule Of Armor Piercing Ammunition Is You Have To Hit The Target”.
3) High Pressures Magnify Velocity Variations: An M-855 powder charge will give a variation of 25-50 fps in production ammunition of a 3,000 fps cartridge at @60,000 PSI. To achieve higher velocities, greater density and energy of the propellant will be required, even compressed powder charges…which through primer and powder interactions makes for wider extreme spreads leading to reduced accuracy and greater dispersion. It’s just harder to burn more tightly packed powder consistently, because the heat transfer of ignition is achieved by a fixed quantity of hot primer gases.
4) The Case Breaks The Cardinal Rules Of Brass Formation: Do not thin or work harden the Brass in critical areas or you will have head or neck separations. The 6.8x51mm has a Non-Obturating Head with higher bolt thrust, so the joint between the stainless Steel case and the Brass case body has both problems and experiences higher forces. Annealing the Brass at the joint will likely make the area too soft for strength, so there is no traditional answer to fix this problem. A two piece metallic case is just one piece too many…
5) Short Barrel And High Pressure Equals Hearing Damage: If fired without a suppressor the sound levels are expected to exceed all issue small arms except the 0.50 BMG…so the short barrel is negated by the urgent need for a suppressor which negates the “compactness” feature.
6) XM-7 Recoils Harder Than Former Champion SCAR-H: When Brass cases are fired, the entire case expands and springs back providing resistance to the case head pushing against the bolt face. This enables small M-4 bolt lugs to resist the pressure, but Steel cases do not perform this way and provide high pressures on the bolt which is transferred as a part of felt recoil to the entire weapon. The rapid pulse of recoil force higher than Brass cartridges due to the Stainless Steel case head has the potential to negatively affect seals and optical assembly epoxies, not to mention in felt recoil. This recoil force reference is per USNWC Crane engineers.
7) The Weapon System Is Neither Compact Or Lightweight: Piston driven carbine actions are typically heavier than other types, particularly in the forend where it affects weapon balance in shooting. This is exacerbated by the addition of a length adding muzzle suppressor however light, lasers and lights on military weapons. When the sighting system is added, the weapon will weigh more than a WW-II M-1 Garand or M-14 that were more than 10 pounds loaded.
8) The XM-7 Design Vents It’s Piston Directly Under And Ahead Of The Optic:
Like all piston powered rifles, the XM-7 vents it’s action directly under the weapon’s forend. When used with a suppressor, piston venting noise is known not to be hearing safe due to increased backpressure. Since sound is pressure, the repeated blasts of >5 PSI are equivalent to what is described for tactical nuclear weapons outside the blast area a quarter mile away. We see no “Blast Overpressure” in MIL-STD-15733 that covers electronics and optics…immersion, hot/cold, humidity, vibration, shock, yes…but no blast. When combined with >80,000 PSI chamber pressure, damage is inevitable.
9) Alternatives Offer Superior Current And Future Armor Penetration:
The competitive Lone Star weapon to the XM-7 pistol length carbine had a full length rifle barrel, which would deliver the required performance on body armor at standard pressures and clearly address improved future armor with high pressure rounds as currently specified.
10) “What They Want Is NOT Always What They Need”:
What they need is to be able to defeat an enemy with NIJ Level IV body armor at any practical range. Instead, “Soldier Touch Points” were used in the decision making process rather than really focusing on what weapon will defeat body armor we WILL encounter now and in the future.
Soldiers will “like” short weapons until they are just as long and heavy as standard ones, make them deaf unless made longer by suppressors, kick the hell out of them and their optics, misses the target, case head separation jams them to death in combat and which won’t penetrate enemy advanced Level IV+ armor from down the block five years from now anyways:
“No weapon is so short and useless that a soldier would not love it.”
11) The Army Says The XM-7 Won’t Last 3 Days:
The most severe indictment of the system is what the recent US Army report stated, paraphrasing; the system has significant flaws… (unlikely to be the spec meeting Vortex optic which was beaten up by blast and record recoil) …which caused it to be combat ineffective within 72 hours.
Source: A guy who heard from some guy who saw some guy see some other guy shoot the rifle.
That report was no more accurate than a book report
Which service rifle was adopted with open arms. Every weapon that has been selected for the US military has been hated when chosen going back to the early 60’s.
So in order:
1-4) Sig apparently outperformed in reliability testing both the other vendors’ submissions. If it had been an issue it would have come up in the three rounds of testing it went through.
5) It’s supposed to keep the suppressor mounted. Is it longer/changing the center of gravity, yes. But that was the requirement.
6) Yeah, it’s got a lot of recoil impulse in comparison to the M4. Pretty much everything does. M7 eating optics would have been evaluated as a part of it’s testing. A lesson learned from the Mk17.
7) ummm… In overall length, minus suppressor it is comparable to the M4A1. For the caliber it fires it is very compact. Is it barrel heavy? Yes, for the reasons you mentioned. That is what product improvement is for: To address these concerns. They did the same thing with the M16/M4.
8) that is what you get with a gas piston design. Especially a short-stroke gas piston. Not sure where you heard the bit about gas regulator noise/blast overpressure, you sound like the reporters who leapt on the fact the M7 had a higher MV than an Abrams like it was something significant. Where’s your evidence?
9) It might have, but the NGSW was contract for a SYSTEM defined as: rifle; automatic rifle; rounds for both. All of which was provided by one vendor. It wasn’t “Pick rifle from vendor A, AR from vendor B” as there was no way that would be possible for the chosen technologies. And the LoneStar AR… was a heavy barreled version of their rifle with a D60 drum. You think the Sig guns are hot, imagine shooting one of the LoneStar AR’s on cyclic with the chamber essentially right under your cheek. Not to mention having to carry 7 or 8 50-60 round drums.
10) So the Army actually asks Soldiers what they want for the first time prior to getting to operational testing, and that’s a BAD thing? Getting Soldier feedback on the Human System Integration aspects was necessary. “Oh they don’t know what they need” … But you do? You’re making some pretty significant assumptions in your scenario there.
11) Umm.. if you are meaning the articles written about the DOT&E report, it sounds like you had your confirmation bias reinforced.