SIG M5 Spear Deep Dive: Is This a Good US Army Rifle?

Published 2022-06-03

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00:00 - Introduction
00:39 - TLDW
01:18 - NGSW history
04:11 - 6.8x51 / .277 SIG Fury cartridge
09:14 - Suppressor
12:53 - Rifle features and disassembly
23:42 - How it handles 80k psi
28:44 - Conclusions and rollout plans

The NGSW (Next Generation Squad Weapon) program began in 2017 to find a replacement for the M4, M249, and 5.56mm cartridge. It came to a conclusion in April 2022 with the formal acceptance of the SIG M5 rifle, M250 machine gun, Vortex M157 optic, and the 6.8x51mm cartridge. SIG released a handful of civilian semiauto M5 / Spear rifles and thanks to Illumin Arms I have one to examine.

The rifle (Spear is its commercial designation; M5 is the military one) is an evolution of the SIG MCX, which is in turn an evolution of the AR-15 and AR-18 systems. The MCX move the recoil spring assembly into the top of the upper receiver, allowing the use of a folding stock. It also has very easily swapped barrels and a suite of fully ambidextrous controls. Scaled up to AR-10 size and chambered for 6.8x51mm, the MCX became the Spear.

That new cartridge (commercial designated .277 SIG Fury) is designed to produce high muzzle velocities out of short barrel (the M5 has a 13 inch barrel).It does this by boosting the operating pressure up to an eye-watering 80,000psi, which required the development of hybrid case using a stainless steel case head. This allows the case to handle those pressures safely. The currently available commercial ammunition is loaded to lower pressure, however. Much of the military and civilian use of this rifle will be done with downloaded training ammunition, which uses a conventional all-brass case.

Both the M5 and M250 were ordered by the Army with suppressors on every weapon, a significant advancement in Army policy. The can is another SIG development, entirely made using additive manufacturing and designed specifically to prevent gas blowback into shooters' faces (which is succeeds at wonderfully).

Overall, I believe the M5 / Spear is an excellent rifle - soft shooting, reliable, and very accurate. However, that does not mean it is the right rifle for the Army. Will its ability to defeat modern body armor prove worth the tradeoff in extra soldier combat load weight and reduced ammunition capacity? Only time will tell...

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All Comments (21)
  • Guile
    We’re all glossing over arguably the most shocking part of the rifle; no bayonet lug.
  • wargriffin5
    US Army: "We've chosen a new service rifle for the future of modern combat."

    Ian: "Today on Forgotten Weapons..."
    I like it, but it definatly requires more charging handles to be exceptionally effective in battle.
  • Niko Mikkanen
    Returning to the ammo needs of the German sturmgewehr: Just about every field test report (frontline troops using it in actual combat) stated that it's a great weapon, but demanded that the ammunition supply must be increased substantially.
  • John Hawkins
    As someone who has worked in additive manufacturing, I have concerns about SIG's ability to mass produce the suppressors in quantities needed for a real conflict. SLM printers (at least the ones I worked with) are slow as hell and can only produce a few units at a time. Given the chamber pressure is so high, it's likely the suppressors will wear out and require frequent replacement. I think a suppressor is a great idea but honestly the more I learn about this rifle the more it seems like it was designed to be a maintenance/service cash cow for SIG and not a truly worthy replacement to the M4. I just don't understand the ammo choice at all. If you're going to go battle rifle calibers, why not use the 7.62x51 cartridge you spent decades convincing other NATO countries to adopt? Swapping from "training" to "combat" rounds is a terrible idea not only in terms of logistics but also because you, uh, shouldn't train your soldiers to a different ammunition to what they'll use in combat? The steel casing contacting the brass has the potential to degrade in storage, is more expensive, requires more logistical and material resources to produce, etc. There's some cool features on this gun but like I said it seems like the epitome of what's wrong with modern defense contractors...
  • Nunya Bznss
    Seems weird to have different rounds. So when troops go to combat, they're going to use a more powerful round that they have no experience with. There's going to be a learning curve that's potentially going to take place in combat.
  • J
    It is disappointing that basically anyone we see shooting it and commenting on how soft shooting it is, isn’t shooting the full pressure ammunition
  • Doug
    I would LOVE to see a post-mortem of Textron's submissions to the competition. Was it poor execution, or is case telescoped ammunition just fundamentally unsound?
  • J P
    The suppressor also makes it for difficult for the enemy to determine where the shots are coming from and eliminates muzzle flash for night operations. That’s primarily the reason the army chose to have the suppressor standard issued.
  • T.M. Nichols
    Thank you for your observations, Ian, and for explaining how the rifle actually handles the 80K chamber pressure. Having spent nearly 40 years working on Army Small Arms, I have a few concerns about this new rifle/cartridge combo. First, is the concept of having 'training ammo,' and 'go-to-war ammo." I foresee units deploying to combat and suddenly discovering that all they have is training ammo. And conversely, going to the range to fire qualification and discovering that they have 'go-to-war' ammo. Next, I'm hoping that the optic has settings for the two different trajectories of the different types of ammo. Next, is the QD suppressor. Some commanders won't want them attached at all, simply because they either don't understand the concept, or for some other trivial reason. They'll have all of the suppressors removed and stored in the Arms Room. When they reach their destination, they'll find that the suppressors are still there - in the Arms Room, back in the States. Don't laugh, I've seen similar things happen too frequently - units that went to war with zero cleaning equipment; units that deployed to a potential war zone and didn't bring any magazines, etc. Alternately, the suppressors will start to 'walk away.' Some entrepreneur will develop an adapter to mount the Sig suppressor on an AR-15, and some soldiers will begin 'losing them' during field exercises. Then the investigations will begin - first by Army CID, then by the ATF, and then by Congress. Time will tell, and I hope that the weapon system is a huge success! I can already anticipate some future modifications to the weapon and changes in procedures, however.
  • goatmurray
    The training ammo reminds me of the whole 10MM thing. I suspect we won't see the high-pressure ammo actually used as much as the training ammo.
  • Retired_Retard
    This is the best discussion I have seen on the new Sig M5 Spear. When the news of this rifle first came out, I thought it might be really heavy. I based that prediction on the weight of the MCX. Turns out it is even heavier than I predicted. I think Ian is among the best sources of good information on the Web.
  • Andrew Mandrona
    Next service rifle will have three charging handles, so there is absolutely no confusion.
  • Randy Havard
    Our troops are going to be in for a big surprise if they train with soft shooting ammunition and then get the combat with something that has substantially more recoil
  • Micha Ols
    A H&K G3 weighed 4,4kg, and the spear weighs 6kg? Wow, that's a lot of weight.
  • Brandon Shofner
    I dont see this rifle having a long service life. 13 pounds (+/-) without the specific optic it will be issued with or any of the other shit like lights, etc is simply to heavy for standard issue. I'm amazed at the weight!
  • Tyler
    It having a rear and side charging handle makes me think of weird made up guns in video games where the artist had no idea how guns work.
  • kathrynck
    You lost me at "13 inch barrel".
    Also, it strikes me that training with de-tuned ammo, will fail to expose shortcomings of the gun/cartridge in peace time. Not to mention failing to acclimate shooters to the recoil & ballistics of the 'combat' round.
  • Eugene Biryukov
    “The recoil spring is under a LOT of compression”
    Ian then pulls out a comically large spring
  • Joe Snuffy
    The M240 will probably be replaced by the 338 Norma version of the new NGSW LMG. That is currently being used by SOF and has the range of a .50 cal, only is man-portable in size/weight.