Until now, the US Army’s 7.62mm XM1158 Advanced Armor Piercing (ADVAP) round has been a mystery. The round, which was rumored to be the basis for the now-cancelled Interim Combat Service Rifle (ICSR) program, is supposed to allow existing weapons in the 7.62x51mm caliber to defeat advanced body armor out to combat ranges. Speculations about its configuration ranged from an improved traditional tungsten cored round to a discarding sabot design firing uranium flechettes, but the answer to this mystery was recently revealed in an issue of the Picatinny Voice. The ADVAP, it seems, is built on the technology of the 7.62mm M80A1 EPR, but using a tungsten core. From the Picatinny Voice article by Audra Calloway:

The XM1158 provides improved performance against a broad spectrum of battlefield barriers and targets typically engaged by dismounted infantry using small caliber ammunition, explained Stephen McFarlane, XM1158 program management lead.

The new bullet is replacing the legacy 7.62 mm armor piercing ammunition, the M993. “In the last decade, many improvements have been made in small caliber ammunition resulting in the improved general propose round, the M80A1 7.62mm Enhance Performance Round (EPR).

The XM1158 retains the improvements ielded in the M80A1 7.62mm EPR with the addition of enhanced hard-target effects resulting from its tungsten carbide penetrator,” McFarlane said.

Tungsten Carbide, abbreviated as WC, is typically used in the penetrator of armor piercing bullets. However, producing WC components at high volumes presents manufacturing challenges. “This in turn has required research in advanced manufacturing techniques, ”said McFarlane. “Without these advanced manufacturing processes, the cost of bullets and time to manufacture them would have increased significantly.”

To mitigate significant cost and schedule impacts, the government invested in a three year Manufacturing Technology effort. That investment proved to be an good investment since it resulted in drastically decreased costs and cycle times for the manufacture of the XM1158 WC penetrator. The successful manufacturing effort enabled the Army to go from baseline processing time of 15 minutes per round, to approximately 25 seconds per round, and achieved significant cost savings. Moreover, the new manufacturing process can be used across the suite of small arms penetrators, which is expected to further extend a substantial return on investment.

“The improvements” of the M80A1 imply that the ADVAP is essentially a tungsten-cored EPR, but there are a number of other possibilities. Perhaps the ADVAP uses a different projectile configuration than the EPR (such as a double-jacketed design with an intermediate aluminum sleeve, or a tungsten-cored OTM configuration), but builds on the EPR design by leveraging the production techniques developed to make the M855A1 and M80A1 possible. This ties into the key aspect of the ADVAP, which is dramatically reduced production time and cost, versus legacy ammunition. Cheaper, quicker to produce armor penetrators don’t solve the fundamental problem of tungsten availability, but they do allow a more liberal and versatile application of such rounds, to supplement standard ammunition. Ultimately, until some of the ADVAP rounds make it onto the collector’s market (which is unlikely to happen very soon, given how rare even M993 and M995 are now), or the Army releases information about it, the exact configuration will continue to be a mystery.

Thanks to Ramlaen for the tip!