https://www.police1.com/police-products/firearms/accessories/ammunition/what-instructors-should-know-about-jacketed-frangible-5-56-ammo

By Benjamin Kurata

During a recent NLEFIA Shoot House Instructor Certification Course, instructors discussed frangible ammunition and its compatibility with suppressors. Students using suppressed rifles reported that some suppressor manufacturers explicitly warn against “conventional” (non-jacketed) frangible ammunition. The cited risk: projectile breakup inside the barrel, which could damage the suppressor and void the warranty.

Warranty concerns appear to stem from a reported (though unverified) incident involving three 30-round magazines of unjacketed frangible ammunition fired full-auto through a suppressed M4 until the system overheated, allegedly causing baffle strikes. (Note: Sustained full-auto fire of this volume is rarely — if ever — necessary or realistic in law enforcement training or operations.)

Several manufacturers now offer frangible projectiles with copper jacketing to help prevent core material from breaking apart in the barrel, reducing the risk of baffle strikes and suppressor damage. This jacketed design appears to be a sensible advancement. However, it raises important considerations that all firearms instructors — especially those in law enforcement — should understand.

Is “jacketed frangible” ammunition real?

Yes. In December 2016, the U.S. Department of Defense (DoD) solicited bids for the Cartridge, 5.56mm, Frangible, Mk311, Mod 3, AA40. Ammunition manufacturers submitted proprietary designs in an effort to secure the contract.

Why did the DoD pursue jacketed frangible ammunition?

A long-standing ammunition manufacturer involved in the DoD solicitation confirmed anonymously that the full-auto incident cited above did occur; however, it involved a polymer-based frangible projectile. Polymer projectiles are highly heat-sensitive. In this case, sustained full-auto fire through a suppressed military M4 generated enough heat to deform the projectile, resulting in suppressor baffle strikes.

Rather than differentiating between frangible projectile compositions, the DoD responded by soliciting jacketed frangible projectiles. NLEFIA could not verify any credible reports of copper-based frangible projectiles coming apart inside the rifle system and damaging a suppressor.

Recommended applications for jacketed frangible ammunition

• Paper or cardboard targets: Accuracy should not be expected to match XM193 55-grain FMJ. The original DoD accuracy requirement for the Frangible, Mk311, Mod 3 was 4.5" average / 6" maximum at 100 yards. This was later relaxed to an 8" maximum due to inconsistent performance.
• Rifle-rated steel shoot houses with intact plywood skins: Avoid repeated target placement in the same locations. Replace damaged plywood and distribute targets to prevent structural degradation.
• Portable bullet traps inside shoot houses: Ensure rifle-rated steel backers and well-maintained plywood faces. Systems incorporating Linatex rubber between plywood and steel significantly reduce internal wear and virtually eliminate back-splatter. Portable stands also disrupt wall-scanning habits and improve threat discrimination.
• Bare, rifle-rated steel targets on a square flat range (SFR): Observe standard FMJ stand-off distances and replace or rotate strike plates at the first signs of pitting or chipping.

The NLEFIA Steel Target Guide, based on decades of empirical use, is available at HERE.

Market considerations

Jacketed frangible ammunition is increasingly available on the open market due to DoD contract overruns. At least two major manufacturers — Lake City Army Ammunition Plant (operated by Winchester) and UDC — are selling excess production, alongside numerous smaller manufacturers.

Identifying true jacketed frangible ammunition

Legitimate DoD-contract ammunition will be identified as:

1. Mil-Spec Cartridge, 5.56mm, Frangible, Mk311, Mod 3, AA40, and/or
2. Compliant with MIL-STD-636 or MIL-STD-1916

Manufacturers that did not secure DoD contracts may still market jacketed frangible ammunition, but their products will not carry these designations.

DoD contracts allow manufacturers to sell overruns on civilian and law enforcement markets, which is often where profitability is realized.

Availability is expected to increase significantly. At the time of this article, the DoD submitted a contract to sole-source this ammunition at multiple millions of cartridges per year for an initial period of eight years.

Important cautions

• Marketing claims do not equate to performance standards.
• Firing ammunition that does not meet SAAMI or NATO specifications can void firearm warranties.
• Duty ammunition should meet FBI testing standards. To date, manufacturers marketing jacketed frangible ammunition for “duty use” have provided no published FBI test data.

Bottom line

Jacketed frangible ammunition should be treated strictly as training ammunition and used under the same safety protocols applied to steel shoot houses and steel targets. Functionally, it should be regarded as comparable to XM193 55-grain FMJ, with reduced accuracy expectations.

Who manufactures “traditional” non-jacketed, copper-based frangible ammo?

There has been significant turnover and acquisition among U.S.-based ammunition companies. At the time of this article, NLEFIA staff were able to verify several sources of traditional non-jacketed frangible ammunition:

• Federal BallistiClean RHT: Available in common law enforcement pistol and rifle cartridges, as well as 12-gauge slug and buckshot.
• CCI Lawman RHT: Available in popular law enforcement rifle and pistol cartridges.
• SinterFire: Offers frangible ammunition with both conventional and lead-free primers. The company also produces frangible projectiles for OEM partners and sells projectiles to hobbyist reloaders.

NLEFIA instructors have fired many rounds from the manufacturers listed above — including through SBRs with suppressors — without experiencing baffle strikes, even when weapon systems were hot to the touch. As always, conduct your own testing and consult manufacturers to ensure any ammunition performs to your expectations.