The intelligent use of artillery has proved a decisive factor in battle after battle, having the ability to rain devastating, accurate fire on enemy troop concentrations.
As artillery technology evolved across previous decades, U.S. Army Yuma Proving Ground (YPG) was on the cutting-edge testing guided and semi-guided munitions capable of hitting within mere meters of a target kilometers away.
In recent decades, one of the innovations tested here was the Modular Artillery Charge System (MACS) that serves as the propelling charges for 155 mm artillery rounds. MACS consists of two types of propelling charges. The M231 is the low-zone component fired either singly or in pairs for shorter ranges, and the M232 is the high-zone component fired in multiples of three-to-five for extended ranges. MACS was developed in the early 2000s as a compliment to the Crusader self-propelled howitzer. MACS was necessary to accommodate the platform’s ammunition autoloader.
“Prior to that, the propelling charges in use by the Army were bag-based,” said Steve Flores, YPG Long Range Precision Fires Cross Functional Team Integrator. “They weren’t very rigid or conducive to putting into an ammunition handling system. The designers made sure the new charges were still compatible with the legacy weapons systems.”
Though Crusader was never fielded, the MACS endured. Since there was a difference in chamber volume and barrel length between the Crusader and legacy systems, compromises were necessary to allow for interoperability across systems. Recently, YPG has been testing improvements to the MACS system for the current generation of artillery. A common ignitor for both the M231 and M232 is also being evaluated to minimize maintenance of the weapon.
“They are reconfiguring and improving upon the charges for use in the current cannon system,” said Flores. “They are improving the way it ignites for more uniformity and to mitigate breech oscillations at high zones.”
Over time, un-uniform powder ignitions can leave unwanted residues in a gun barrel, and oscillations can eventually create reliability problems for a howitzer’s firing mechanism.
“Another key piece of data propelling charge designers require is how the gun tube is wearing after firing the new charge,” said Flores. “They need to know if it is wearing faster than with the legacy charge.”
YPG’s ammunition plant has been instrumental in building multiple experimental formulations, shapes, and configurations for new propelling charges
“Every time the product manager has an experiment they want to try out, all of the propelling charges and ignitors are hand assembled at the ammo plant,” said Flores. “The ammo plant will assemble them to the customer’s instructions in any and all combinations of things.”
In test fires of the MACS, the velocity of the fired round is measured. As each round is in flight, workers back at the howitzer take readings from pressure gauges inside the gun barrel. Testers also look for residue in the gun tube, using a camera aimed at the breech during the test and physically inspecting it after the round has been fired. For these tests, however, inert rounds are fired.
“For testing propellant you don’t really need the actual high explosive round, you just need something that is representative,” said Flores. “We intercept empty projectile shells at the factory before they are filled with high explosive and carefully load them with wax to the exact weight of a high explosive round and put an inert fuze fabricated at YPG on it. The propellant does not know the difference between that round and an actual high explosive round.”
Whenever the United States military fires an artillery round, the reliability of that round was meticulously proven at YPG long before making it into the hands of Soldiers.
“There is no other facility that is a one-stop shop, from the ammunition plant that hand-assembles these items to having ready access to all of the different cannons,” said Flores. “We have experienced weapons operators, sophisticated test instrumentation and infrastructure, a large range, and specialized gun tube inspection capabilities.”
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