U.S. Marine special operations forces recently chose the Glock 19 as their official sidearm, but this isn't the first time elite units have invested in the Austrian pistol maker.

The U.S. Army's 75th Ranger Regiment decided to pure-fleet its battalions with the Glock 19 in September 2015, according to an Army source familiar with the decision who is not authorized to speak to the media.

Four months later, U.S. Army Special Operations Command followed the Ranger Regiment's example and chose Glock 19 for the rest of its forces, including all Special Forces Groups and the 160th Special Operations Aviation Regiment, the source said.

Elite units had routinely authorized personnel to carry the Glock 9mm pistol instead of the standard-issue M9 9mm pistol.

But this latest decision by Marine Corps Forces Special Operations Command, or MARSOC, to follow Army special operations forces in choosing to use only the Glock 19 speaks to Glock's standing in the world of military sidearms.

"It came down to feedback from the field," MARSOC spokesman Maj. Nick Mannweiler told Military.com on Tuesday. "We determined that the Glock 19 met the requirements that we needed for a concealable, reliable pistol that fired a 9mm round."

Army Special Operations Command has not agreed to Military.com's interview request, but the Army has paid more than $5 million to Glock Inc. since September 2015.

The compact Model 19 is one of Glock's most popular handguns. The striker-fired, 9mm pistol features a four-inch barrel and has a standard capacity of 15 rounds, although 17-round magazines are available. The polymer frame features an accessory rail for mounting lights.

MARSOC'S move follows a Marine Corps decision in February that authorized MARSOC operators to carry Glock pistols, since many of the elite outfit's members prefer the popular Glock 19 9mm handgun over the custom .45 pistols the service bought them in 2012.

The Corps completed an exhaustive search for a new MARSOC pistol in 2012. The service awarded a $22.5 million contract to Colt Defense LLC for up to 10,000 Close Quarter Battle Pistols.

But MARSOC officials decided it would be better to streamline its pistol inventory down to one sidearm, Mannweiler said, adding that the command has purchased 1,654 Glock 19s.

"That is the standard-issue sidearm now that you will see," he said. "You are not going to see 9mm M9 Berettas; you are not going to see the Colt 1911. You are going to see Glock 19s as the issued sidearm."

Army's Modular Handgun System

Glock is also competing against a handful of well-known pistol makers for the chance to make the Army's Modular Handgun System. The Army launched its long-awaited XM17 MHS competition in late August to replace the service's Cold War-era M9 9mm pistol.

Sig Sauer, Beretta and FN Herstal are also competing for the MHS contract. The Army recently notified Smith & Wesson that it would not be advancing to the next phase of the competition.

Army Chief of Staff Gen. Mark Milley has considered bypassing the multi-year MHS effort and following Army Special Operations Command's decision to buy Glock 19s.

Earlier this spring, Milley publicly criticized the MHS program's 356-page requirement document and lengthy testing phase, slated to cost $17 million for technology that has existed for years.

The chief also asked the Army Special Operations Command's G-8 office, which oversees fielding of equipment, if there was room for the Army to join the pistol contract to buy Glock 19s, according to the Army source.

Milley has since backed off of his criticisms of MHS and in early October said the program was "on track."

If Glock wins the MHS contract, it stands to replace the 400,000 M9 pistols in the Defense Department's inventory since the Army is the Pentagon's executive agent for small arms.

For now, Glock is staying quiet. Company spokeswoman Brandi Collins declined to comment on its recent success in the special operations world.

The results are obvious by the delivery numbers. Since September 2015, the Army has taken seven delivery orders from Glock, totaling $5.6 million. Notably, the Army paid Glock $1.7 million on Feb. 16 and $3.5 million on March 23.

New Glock 19s retail for $500-$600 each, but the Glocks for U.S. Army Special Operations Command currently cost about $320, the source said.

-- Matthew Cox can be reached at matthew.cox@military.com.