Whether it is destroying targets, illuminating rounds to light up areas at night, or projecting white phosphorous rounds to provide smoke screens for American troops, the mortar has proven capabilities in America’s wartime arsenal.
However, with any wartime capability, accurate testing can only ensure the Warfighters success in a mission to defeat the adversary, and that highly-complex and rigorous testing starts at U.S. Army Yuma Proving Ground (YPG).
The U.S. Military uses three calibers when it comes to mortars: 60mm, 81mm, and 120mm. The muzzle- loaded weapon consists of a ballistic tube attached to a base plate that is propped up by a bipod. But what is said to be more important is the projectile used within the mortar to assist in battleground combat.
The cartridge for a mortar is multifaceted and made up of many parts such as an ignition cartridge, propellant, and propelling charges, which ultimately leads up to the full encapsulated cartridge that is fired out of the tube.
Each part is produced, tested, and issued in batches according to test officer Kayleigh Caparulo with YPG’s Munitions and Weapons Division. Phase one of the testing typically starts with the propellant, followed by the ignition cartridges and propelling charges.
Batches of M47 propellant from private industries working with the federal government can consist of a few thousand pounds. But before it can be used towards battle efforts, a team of more than a dozen at YPG are responsible for making sure it maintains the same quality as the previous batches used in the past.
“Once we reach the end of that propellant lot, we have to test it again,” Caparulo said. “Scientifically it is exactly the same, but as with anything made out of chemicals the balance is just a little different and that is why we have to test it again.”
Using wax projectiles, the team is able to focus solely on how the propellant is reacting when the round is ignited. To stay consistent with its real-time use in the battlefield, the 120 mm mortar being used for this test is planted inside a military grade vehicle, simulating how it would be used by Soldiers on the frontline.
The projectile is attached to a lanyard and placed within the tube from the top. This allows the test officers and gun crews to release the projectile from the lanyard from a safe distance to test the round. For this specific test, the team is looking at how the batch of M47 propellant reacts when fired.
“The main things we look at are muzzle velocities at the right speeds, and are the chamber pressures within the expected parameters,” Caparulo explained. Some of this data is also recorded from high speed video cameras placed around and on top of the 120mm mortar.
To ensure accurate testing of the M47 propellant, the team fired 40 wax projectiles to get accurate sampling of the propellant.
The team performed a second firing later in the week with 60 wax projectiles to confirm the amount of propellant calculated performs to specifications.
“Once the propellant gets tested we can go into making the propelling charges and ignition cartridges which then leads up to full cartridges,” Caparulo said.
Test launches are conducted for each portion of the cartridge. Caparulo said it can take months and even as long as a year before the cartridge is finalized and used amongst American forces in combat situations.
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