First there were the Camo Wars, now there are the Caliber Wars. The multiplicity of small arms calibers and platforms is an issue that has become increasingly clear over the past couple of years, and it reflects a standardization and logistics situation that really needs to be addressed. Now legendary former Delta Force Operator and renowned firearms expert Larry Vickers has published an article that cuts to the heart of this issue, which he very accurately describes as a cluster****.

In his article he calls out the fact that between them US military branches are currently fielding numerous types of shoulder-fired small arms firing a mind-boggling 8 different calibers of ammunition across 15 different weapons platforms – and we’re not even counting machine-guns or sub-machine guns!

Now, there are valid reasons for this situation due to specific functions or roles, which we’ll look at below, but as LAV points out, this makes for a logistical nightmare even in peacetime. I will put the link to Larry Vickers’ article at the end of this piece, but first I thought it would be useful to provide a visual catalogue of the systems and calibers in current use:

The current standard rifle across all branches except the USMC, and chambered in NATO-standard 5.56x45mm caliber. Current US Army inventory stands at approximately 480,000 units, with contracts awarded for up to an additional 30,000 by 2030.
FN SCAR-L in NATO-standard 5.56x45mm caliber. Originally developed for SOCOM but only ever saw limited service with the Ranger Regiment. These have now been withdrawn from service.
USMC M27 Infantry Automatic Rifle, chambered in NATO-standard 5.56x45mm caliber. It is the USMC’s standard issue rifle.

 

USMC M38 Designated Marksman Rifle, chambered in NATO-standard 5.56x45mm caliber. The USMC’s squad level DMR version of the M27.
HK 416D, chambered in NATO-standard 5.56x45mm caliber remains in limited active use with certain US SOCOM (Special Operations Command) units, particularly in Navy SEAL teams and some Delta Force/JSOC elements. Fielding is gradually declining as newer platforms like the SIG MCX, Noveske N4, and LMT platforms are being adopted (also in 5.56x54mm caliber).

 

Not mentioned in Larry Vickers’ article, but still in the inventory, the Mk 14 Enhanced Battle Rifle (EBR) is a modernized version of the M14/M21 rifle designed for the DMR role , chambered in 7.62×51mm NATO.

 

KAC M110 Semi-Automatic Sniper System (SASS), in NATO-standard 7.62x51mm caliber. About 2,000 units in service with the US Army.
HK M110A1 SDMR is replacing legacy M110 and M14 EBRs as the Army’s standard squad-level designated marksman rifle, chambered in 7.62x51mm NATO caliber. Approximately 6,000 units have been fielded so far.
Around 750 FN SCAR-H (Mk 17) rifles were purchased by U.S. Special Operations Command (SOCOM) units as semi-automatic sniper rifles. It is chambered for the 7.62×51mm NATO cartridge.

 

Also not mentioned by Vickers, but still soldiering on in active service, the M107 semi-automatic long-range anti-materiel rifle is chambered in .50 Browning caliber. Approximately 2,000 units are in use with Army, Marine Corps, and Special Operations Command units.
The US Special Operations Command (SOCOM) MRGG program (Mid-Range Gas Gun) is an initiative to field new rifles chambered in 6.5mm Creedmoor to give operators improved range, accuracy, and lethality compared to existing weapons. The MRGG-A (Assault rifle) contract was awarded to Lewis Machine & Tool (LMT) Defense in August 2025. The MRGG-S (Sniper/Designated Marksman Rifle) awarded to Geissele Automatics earlier in 2023. 

 

The US Army’s M7 Next Generation Squad Weapon (NGSW) rifle is currently being fielded primarily within the Close Combat Force units, including infantry, cavalry scouts, combat engineers, and combat medics, to replace the M4 carbine. The M7 fires a unique new 6.8×51mm cartridge, offering greater range and lethality effects than the 5.56mm M4.
The .300 Blackout caliber SIG MCX Rattler is primarily used by U.S. Special Operations Command (SOCOM) units as a personal defense weapon (PDW).
Delta Force is experimenting with the Surefire MGX in 6mm ARC caliber.

 

Not mentioned in Larry Vickers’ article is another experimental / developmental effort – the FN IWS (Individual Weapon System) chambered in a new .264 / 6x43mm cartridge under the auspices of the Irregular Warfare Support Directorate. Sponsored by Canadian SOFCOM, the IWS has achieved NATO standardization classification but its future adoption status is unknown at the present time. In my opinion, it appears to offer significant advantages over the current 5.56x45mm NATO caliber and would provide an optimum intermediate caliber choice for general purpose squad level rifles, carbines, DMRs, and light machine-guns – without the significant weight and bulk issues of either the 7.62x51mm NATO or 6.8x51mm NGSW calibers. 6.8x51mm NGSW does clearly outperform 7.62x51mm NATO as a long range marksman and machine-gun caliber though.

 

Mapped out like this it becomes pretty obvious that the US military is not only facing a complex mix of different weapons platforms to perform the same of very similar roles, but also a number of different calibers and cartridges. If it’s making your head spin, imagine if you were in charge of the logistics to support all of this? To say nothing of the interoperability challenges between service branches and international allies!

Larry Vickers makes a very salient comparison between the situation the US military has created for itself, and the situation the German military found unsustainable in WWII. You can read his article here.