At a time when just about every pistol in the U.S. military was chambered in 9mm, the U.S. Marine Corps doubled down on a new M1911A1 style .45 auto. 

The Marines, of course, are no stranger to the M1911, having-- alongside the Army and Navy-- begun issuing early Colt Government Issue models in June 1912. Holding with the "GI 45" through the Great War, the Banana Wars, World War II, the Korean War, Vietnam, Grenada and Lebanon, Marines were still carrying standard M1911A1s well into the late 1980s even as the service was replacing the gun with the then-new Beretta M9 (92F), a 15+1 double stack 9mm that offered twice the capacity of the old .45. 

After about 1990, the only M1911A1s in the Marines were rebuilt MEUSOC guns in the Fleet and National Match models used by shooting teams

That didn't mean the M1911 was completely down and out with the USMC moving into the 1990s. Marine Corps armorers constructed special Marine Expeditionary Unit (Special Operations Capable), or MEUSOC, guns from old WWII-era GI frames, and a variety of high-speed aftermarket parts. These guns, augmented by a few unit-purchased Springfield Armory M1911A1s, remained in use with select units. 

Fast forward to 2012 and this stop-gap method of relying on a mix of elderly guns diluted with small buys of commercial firearms wasn't sustainable, and the Marines went looking for a more specialized replacement, the Close Quarter Battle Pistol.  

Enter the General

In 2002, retired Lt. Gen. William M. Keys, a Vietnam-era Navy Cross recipient and the man who led the 2nd Marine Division during the liberation of Kuwait in 1990, took over the reins of the flagging Colt's Firearm company and led managed to turn it around over the course of a decade.

During that time, Colt introduced a series of railgun M1911 Model O pistols in 2009, which included a Picatinny accessory rail on the frame just forward of the trigger guard. The Model Os included such standard features as a Novak rear and dovetailed front sight, an up-swept grip safety, and a National Match Stainless barrel. 

It was this gun that the Keys-led rebooted Colt further modified with a dual recoil spring assembly and all-stainless internals and pitted against Springfield Armory's Operator model for the shot at being the Marine Corps' new .45. In the end, the Colt gun got the nod in July 2012 with a five-year $22 million contract to provide as many as 12,000 new railguns to the USMC, a pistol dubbed the M45A1 CQBP.

Ironically, the contract was issued 100 years and one month after the first shipment of early M1911s were acquired by the Marines. 

The M45A1 CQBP has been in use with Marine Expeditionary Units deployed with the Fleet since 2013. (Photos: USMC) 

Sadly, the days of the .45 in USMC service are numbered. As noted in the Navy’s FY 2019 procurement budget justification for the Marine Corps, 35,000 Sig Sauer M18s 9mm pistols will not only replace the service's M9s but also the M45A1 railgun and the newly-acquired M007 Glock.

Commercial models

Since 2017, Colt has been offering a commercial variant of the M45A1 CQBP with either a Decobond FDE or a two-tone finish over a stainless steel receiver and slide. Other features include Novak sights, an enhanced hammer, solid aluminum trigger, National Match barrel, black G10 grips, and a flat, serrated mainspring housing.