Ever since American police forces began switching from revolvers to semi-auto pistols in the 1980s, there has been a controversy over the cartridges they have been chambered for. While 9mm Parabellum was the original choice of most departments, street officers soon began asking for a more powerful round, yet they wanted it in a pistol that was also light enough to carry comfortably all day whether in a holster or concealed. The .40 S&W and .357 SIG rounds provided more punch, but there was still a significant number of agencies and officers who wanted bigger bullets.
It is a well-known fact that most American handgun shooters — LEO and civilian — have had a long love affair with .45 caliber handguns. Glock sought to address this market with its G21 pistol firing the .45 ACP cartridge. But as I said at the beginning of this report, the G21 can be quite a handful.
Glock received enough requests for a .45 pistol of manageable size that it introduced the G37 chambered for the .45 GAP cartridge. The .45 GAP provided .45 ACP-like ballistics from a pistol built on the company's small frame. While the G37 has become moderately popular in law enforcement circles, the fact remains that when it comes to .45 pistols, most officers want the real thing, a .45 ACP pistol.
Keeping in mind the old adage that "the customer is always right," Glock sent its engineers back to their CAD programs. And they came up with a rather simple solution. Reducing the size (depth) of the large frame's backstrap resulted in a trigger reach of 2.87 inches as opposed to the 2.95 on a standard large-frame Glock. The new pistol was dubbed, appropriately enough, the G21SF or Glock Model 21 "Short Frame."
But the smaller frame is not the only thing that makes the G21SF unique: It is also the first Glock pistol to feature ambidextrous magazine release catches.