Mortar training rounds tested as rigorously as other rounds at U.S. Army Yuma Proving Ground

By Mr. Mark Schauer (ATEC)December 10, 2015

Mortar training rounds tested as rigorously as other rounds at U.S. Army Yuma Proving Ground
Weapons operator John Devine (right) loads a M769 full range practice mortar round for a test fire. The inert round, which has the shape and characteristics of the 60-millimeter mortar round commonly used by combat infantrymen, is tested just as rigo... (Photo Credit: U.S. Army) VIEW ORIGINAL

YUMA PROVING GROUND, Ariz.-- U.S. Army Yuma Proving Ground's primary mission is to test equipment to ensure it works anywhere in the world. This includes virtually everything in the ground combat arsenal, including items that are meant for training men and women in uniform for combat.

The M769 Full Range Practice Round, which has the shape and characteristics of the 60 mm mortar round commonly used by combat infantrymen, is one such item. Though not used in combat, the Army and Marine Corps fully rely on the M769 to function safely and effectively in training situations.

"Like anything else, it has a specification the manufacturer is contractually obligated to meet: that specification is what the customer is asking for and paying for," said Brett Bowman, test officer. "Soldiers may be training with observers close by, and you don't want any abnormal flight characteristics that could potentially harm nearby personnel."

Toward this end, YPG testers conduct lot acceptance and cartridge testing on training rounds that are every bit as rigorous as any other projectile. Lot acceptance testing, the testing of a sample of munitions to ensure reliability, is a large part of YPG's munitions testing workload.

"When we perform lot acceptance testing, we test everything from the primer, the fins, the propellant, the body, and the fuze," explained Bowman. "This is a test of all of those past lots combined into a cartridge test, fired as it would be shot in combat."

Though mortar cartridges are relatively small and simple, the cartridge's body integrity and components like the ignition cartridge must be tested for performance and safety. Likewise, performance characteristics of the cartridge, such as velocity, pressure, and range, must conform to set specifications.

"These particular cartridges are completely inert. The only energetics are in the fuze with a shotgun-like shell that has a signature of flash, bang, and smoke to give both audible and visual observation of function. When you are training people on a system, you don't want them using high explosives while not knowing the system well."

Nonetheless, weapons operators and test personnel adhere to the same safety procedures they do when conducting evaluations of live rounds, such as firing the mortars remotely from behind a bombproof shelter. Likewise, the data gathered is similar to live mortars. Pressure transducers inside the mortar tube measure the pressure generated by the mortar's firing and two muzzle velocity radar units measure the velocity of the mortar in flight. High-speed cameras photograph the projectile 20 feet from the muzzle to ensure that metal parts, like the stabilizing fins that help it fly, remain intact, and another camera captures a close up look at the fuze to verify it has been set during firing.

"The main quantitative data that qualifies the rounds is our range standard deviation along with several other factors detailed in the MIL-SPEC for that type of round. We have observers downrange triangulating the impact location of the round to ensure it falls within its requirements."

Despite the high tech equipment, human observers are still critical to a successful test.

"We have backups for everything. If one misses it, others catch it," said Bowman.

After each mortar round is fired, Bowman reviews high-speed footage and waits for the pressure and velocity to be announced before calling for another round to be loaded. This pace is maintained until the last of the lot's rounds are fired.

While other test centers possess adequate land to conduct these tests, customers continue to choose and return to YPG for its flexibility and the ability to recover tested mortar projectiles. In addition to having crowded, heavily scheduled ranges, some test centers have firing ranges that are too contaminated by unexploded ordnance and other hazards to permit retrieving the remains of a fired projectile for examination, a problem that doesn't exist at YPG.