YUMA PROVING GROUND, Arizona - What weighs 24 pounds and fires 800 rounds per minute with deadly precision?

Armchair enthusiasts know it as the Heckler and Koch 121, but the German army has designated it the MG5 -- a replacement of the MG3, the design of which dates back to World War II. The MG5 fires standard 7.62 North Atlantic Treaty Organization cartridges, has modern sighting optics that greatly improve the weapon's accuracy over its predecessor, which only had iron sights, and NATO rails for mounting additional equipment like lights and radio equipment.

"This machine gun can also be fired while standing, which wasn't possible with the old one," said Col. Christian Brandes, infantry chief for the German army's Concepts and Capability Development Center. "We're not losing that much weight, but in all capabilities it is better than the MG3. Its main feature is that it is much more accurate than its predecessor." The MG4, a smaller weapon, will continue to be used.

The German army is eager to adopt the new, more-versatile weapon for its infantry, but first wanted to subject it to rigorous operational testing in realistic natural environments. U.S. Army Yuma Proving Ground met the needs for this.

"Our intent was to find out if the machine gun meets our requirements in hot and dry conditions," explained Brandes. "If it is treated badly under rugged, very hot conditions, will it still operate?"

Germany's temperate environment lacks the extreme conditions German soldiers have faced in recent years in places like Afghanistan.

Prior to fielding the new weapon, the testing was conducted to answer a number of questions: How well can the weapon be handled by infantrymen whose hands are slippery with gritty sweat? Is the weapon's optical sight compatible with infantrymen wearing sunglasses? Does the machine gun's bipod provide a suitable grip on sand or rocky desert pavement? Will it still function in dust and dirt, even when it isn't cleaned for several days? American Army testers ask similar questions when testing its own equipment.

Led by Brandes, two German Army infantry squadrons, one mounted and one airborne, participated in the live fire test, conducting simulated missions across one of YPG's live fire 'smart' ranges with automated pop-up targets erected by YPG's Training and Exercise Management Office. All the German non-commissioned officers had past experience serving in Afghanistan.

Though YPG is primarily used for testing, the installation's training ranges are robust enough to accommodate the needs of multiple units simultaneously. In fact, while the Germans were testing, members of the Arizona National Guard were conducting live fire training on a nearby range without anything beyond the sound of gunfire noticeable to others.

"We are on the proving ground, so there are tests in progress that they are not privy to," said Luis Arroyo, training and exercise management office chief. "The good thing is that our ranges are generally away from the test ranges."

Of course, there were administrative hurdles to overcome in the months prior to the German test.

"Transferring weapons of war from one country to another is always a big issue," explained Brandes. "We wanted to test in a NATO country -- and only one country -- so we wouldn't have to move the weapons over a border more than once. We also wanted to ensure the climate was as extreme as possible."

For this reason, the tropical portion of the test following the desert portion at YPG took place in Hawaii rather than facilities used by YPG's Tropic Regions Test Center in Panama and other South American countries.