YUMA PROVING GROUND, Ariz. - U.S. Army Yuma Proving Ground is the Army's premier range for artillery testing.
A grand total of the tonnage of artillery fired at YPG across its seven decades of existence would be a staggering figure. Yet few individual tests in the proving ground's history could rival the nearly 3,000 artillery rounds fired over the course of 11 days this past December.
"The sheer volume of artillery fire was impressive," said Kermit Okamura, munitions and weapons division chief. "In that time period we fired 20% of what we did the previous year in all 155mm artillery."
Some in the surrounding community fancifully assumed that the audible multi-day fusillade was an early celebration of the upcoming new year, but the reality was far more serious: the usability of the M109A6 Paladin self-propelled howitzer hung in the balance.
For more than 40 years, variants of the M109 have been the most potent self-propelled howitzer in the Army's arsenal, able to rapidly deliver a punishing barrage of steel downrange across a wide radius of the battlefield, from the jungles of Vietnam to the rugged mountains of Afghanistan. Since first fielded, the M109 has undergone six major changes, all of which were tested at Yuma Proving Ground. Over the years, the cannon's range has been doubled, the stowage space for artillery shells has been increased, and sophisticated digital communications, fire control and navigation systems added.
In some turreted vehicles, the gun barrel needs to have a bore evacuator which in turn is connected to the barrel's interior via a series of evacuator holes. The bore evacuator collects high pressure gas as the projectile passes by the holes then vents that same gas once the pressure inside the barrel has subsided. The venting of this gas evacuates fumes and gases out the muzzle end of the barrel. This protects crews inside the vehicle's cab from potentially dangerous levels of gases left behind from a projectile's firing. Unfortunately the bore evacuator holes are susceptible to corrosion and pitting.
M284 Cannon tubes that are no longer serviceable due to corrosion in the bore evacuator holes can be reclaimed. Army personnel had a fix in mind for this problem: bore out the rust surrounding a given evacuator hole, then press a corrosion-resistant bushing into the now-larger hole to bring it back to its original size. It was imperative that this fix be tested in a safe environment prior to being performed on gun tubes that could potentially be used by Soldiers. YPG was tasked to do so on a very compressed schedule: firing nearly 3,000 rounds from three gun tubes in no more than two weeks.
"Part of the nature of the job is you might have to practically live out here for a short period of time," said Schilders. "If war demanded it, we'd be required to. It's nothing Soldiers don't do, though."
YPG personnel stood ready to support the test, but there were a slew of hurdles that had to be overcome. Fortunately, scheduling conflicts that would otherwise have been inevitable at the Army's busiest proving ground were not a problem so close to the Christmas holiday.
"We got lucky," said Okamura. "Because of the timing, the range was relatively slow. We were able to pull resources to accomplish the mission."
There were other potential challenges, as well. Would large fans be necessary to disperse the gun smoke from such a rapid rate of fire? Was enough ammunition available? Ammunition planning at YPG is usually accomplished months in advance, a luxury that wasn't possible for this test given the urgency.
"This was quite a challenge," said Steve Flores, Artillery and Mine Branch Chief. "The problem was if we used everything we had, we wouldn't have enough 155mm ammunition for upcoming projects."
Using three howitzer tubes identified for the testing, firing proceeded at a rate of one round every two to three minutes for most of the 11 days of testing: the only lulls occurred to accommodate inspections of the tubes during shift changes.
"The quicker we got the inspection and measurement data, the sooner we could get rounds fired again," said David Le, mechanical engineer in YPG's physical test facility. "In my entire career at YPG, I have never seen a program fire in 24-hour blocks at top charge."
This pace was even more impressive considering that each round was remotely fired, a different process than firing it as Soldiers in theater would. The pace of the evaluation of the third tube was far slower and more methodical that those of the other two. It was also more heavily instrumented, with high speed cameras filming each shot. The tube was artificially induced to fail after nearly 300 rounds fired, producing valuable engineering test data.
"Ordinarily when we test, we aren't expecting anything to fail, but we are ready for it," said Flores. "There is a certain level of risk to equipment that we accept. Since we were inducing a failure for this test, we took additional precautions for all instrumentation and vehicles, and conducted extra safety briefings and warnings for personnel."
The pace was ambitious and for the duration of the test YPG was at the center of the Army's attention, but personnel involved in the testing took it in stride.
"People understood the urgency, but it didn't look like the world was on fire," said Okamura. "Other than the high visibility and short test timeline, you wouldn't have noticed any difference in the way operations were going. The professionalism across the board was awesome."
In all, the extraordinary efforts of well over 100 workers made the test a shining success.
"They were able to validate that the interim fix was suitable to get them to a long-term fix," said Okamura. "The final product was ATEC providing a safety confirmation recommendation that will be issued with those newly modified tubes."
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