Next Generation Squad Weapon (NGSW)

In April 2022 Sig Sauer was awarded a contract for the Next Generation Squad Weapons or NGSW program, their entry consisted of,

The XM7 magazine fed rifle with a 13.5-inch barrel,

The XM250 belt fed machine gun with a 17.5-inch barrel,

And the .277 fury bi-metallic cartridge capable of achieving chamber pressures of 80000 PSI, using either the 135-grain surrogate projectile or Sigs own 121-grain General purpose projectile,

The XM1186 general purpose projectile will be of the Enhanced Performance Round or EPR type, with a hardened steel penetrator and copper slug encased in a copper jacket.

An entire family of 6.8mm ammunition is in development including general purpose, tracer, special purpose, and reduced range projectiles.

The special purpose projectile will likely be an aeroshell type projectile with a polymer aeroshell and a tungsten core.

Using a Powley Computer, the muzzle velocity of the 121-grain general purpose projectile can be calculated, calibrating the system using a 135-grain projectile fired from a 16-inch barrel with its reported muzzle velocity of 3000 feet per second. The XM7 should have a muzzle velocity of about 3040 feet per second and the XM250 should have a muzzle velocity of about 3200 feet per second.

In order to reduce the overall mass of the ammunition the projectile calibre could be reduced, and the projectile, propellant and case masses would be accordingly reduced, however as the projectile becomes smaller the sectional density would also be reduced, reducing the penetrative capability of the projectile.

This will reduce the armour penetration range of the projectile and so this disadvantage must be weighed against the advantage of making the ammunition lighter.

In order to reduce the mass of the cartridge, the high pressure bi-metallic case was initially designed with an aluminium washer to press the thin copper sleeve into the steel base, this was later simplified to pressing the copper sleeve directly into the steel base.

It has been reported that .277 fury is 23.5 percent lighter than its equivalent energy cartridge, the .270 Winchester short magnum at about 29 grams, resulting in a cartridge weight of roughly 22.2 grams with a 135-grain projectile or 21.3 grams with a 121-grain projectile.

Using measured .277 fury cases weighing an average of 10.06 grams we can calculate an approximate mass of the cartridge as 22.11 grams with a 135-grain projectile or 21.20 grams with a 121-grain projectile.

The overall loadout of the XM7 will likely be around 21.7 pounds with 140 rounds compared to the M4 loadout of 15.5 pounds with 210 rounds.

The overall loadout of the XM250 will likely be around 38.9 pounds with 400 rounds compared to the M249 loadout of 37.7 pounds with 600 rounds.

Only time will tell if the NGSW program will lead to these new weapons being adopted or not.

I initially assumed that the XM1184 SP projectile would be an aeroshell type projectile as the cross section on slide 6 was blacked out, however, I have since found more information about the M1158 ADVAP projectile and I assume that this could be the basis of the XM1184 SP projectile, at least initially.

The M1158 ADVAP projectile is similar in design to the M80A1, with the hardened steel core penetrator replaced with a tungsten carbide penetrator, and the copper slug replaced with a steel slug.

Since I cannot access the research paper I had to estimate the projectile masses myself using information I found about the projectile on a Google search.

I modified an excel spreadsheet from the EPA and used values of density for the tungsten carbide penetrator at 14.6g/cm^3, as the paper I found the image from states that the tungsten carbide penetrator has a mass of about 86% more than the hardened steel penetrator, which also agrees with another paper that states that is the density of current US tungsten carbide penetrators.

I also used a density for 4340 steel at 7.85g/cm^3 which is the steel used in a YouTube simulation of the M855A1, which I assumed to be the same type of steel used in the M80A1.

I have calculated the mass of the M1158 at around 162gr, and the XM1184 at around 150gr by multiplying the mass increase from the M80A1 to the M1158 by the mass of the XM1186.

Clarification of values on slide 8;

The pressure for the 135gr surrogate projectile does give 3000 feet/second but it drops to 2999 once that value of pressure is locked in.

Images/Screenshots and Information credit:

 

www.youtube.com/watch?v=w07HkVqn09Y

www.army.mil/article/255827/army_awards_next_generation_squad_weapon_contract

www.guns.com/news/2020/07/13/which-weapon-could-be-the-armys-new-rifle-light-machine-gun

www.military.com/daily-news/2019/10/27/inside-armys-quest-revolutionary-new-bullet.html

ecf.cofc.uscourts.gov/cgi-bin/show_public_doc?2011cv0084-112-0

soldiersystems.net/2021/01/27/sig-ammunition-produced-rounds-of-6-8x51mm/

www.gunsandammo.com/editorial/ngsw-sig-sauer-us-army-contract/457100

www.youtube.com/watch?v=LeGyFwIhGuE

www.americanrifleman.org/content/return-of-the-rifleman-the-next-generation-squad-weapons-program/

kwk.us/powley.html

uklandpower.com/2018/10/19/the-us-armys-next-generation-squad-weapon-programme/

forum.cartridgecollectors.org/t/actual-sig-sauer-6-8x51mm-next-generation-squad-weapon-composite-cartridge-case/52615

forums.delphiforums.com/autogun/messages/7519/231

forums.delphiforums.com/autogun/messages/7519/1626

forums.delphiforums.com/autogun/messages/7519/2958

ndiastorage.blob.core.usgovcloudapi.net/ndia/2022/future/Tues_Grassano.pdf

www.militarytimes.com/off-duty/gearscout/kit/2019/06/11/socom-wants-a-new-armor-piercing-sniper-bullet-heres-one-option-engineers-are-developing/

www.google.co.uk/search?q="m1158"+projectile+mass&sca_esv

journals.sagepub.com/doi/abs/10.1177/15485129241240768

journals.sagepub.com/cms/10.1177/15485129241240768/asset/images/large/10.1177_15485129241240768-fig1.jpeg

dspace.lib.cranfield.ac.uk/server/api/core/bitstreams/f5e0588d-e970-4551-9211-45ae3834d54c/content

www.researchgate.net/publication/268803431_Ballistic_impact_experiments_of_tungsten_carbide_projectiles_onto_tungsten_carbide_targets

view.officeapps.live.com/op/view.aspx?src=https%3A%2F%2Fwww3.epa.gov%2Fregion1%2Feco%2Fdrinkwater%2Fcapecod%2Fadminrecord%2FMass-Analysis-of-Bullet-Components-for-Proposed-MPMGR.xlsx&wdOrigin=BROWSELINK

www.youtube.com/watch?v=2iSOP87G4z8

www.army.mil/article/256697/ngsw_signifies_an_evolution_in_soldier_lethality

media.defense.gov/2022/Apr/20/2002981026/-1/-1/0/220420-O-D0439-002.JPG

www.usord.com/weapons/m249