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The .45 Gap Glock Model 37

The Glock 37 is essentially a .45-caliber pistol the size of a 9mm Glock 17 and .40-caliber Glock 22. The Glock 37 fires a brand-new pistol caliber, the .45 Glock Automatic Pistol, known as the .45 Glock, or more accurately, the .45 GAP. This caliber is very similar to the .45 Automatic Colt Pistol, known as the .45 ACP or .45 Auto. The .45 GAP uses a shorter, stronger cartridge case but fires exactly the same .451-inch diameter bullets to the same velocities as the .45 Auto.

The big deal with the .45 GAP is getting .45-caliber performance and higher ammo capacity in a standard frame pistol. Glock’s standard frame is much easier to securely grip than its large frame Model 21, and the Glock 37 holds more ammo than its subcompact Model 30 and Slimline Model 36.

45 GAP Cartridge

The .45 GAP is a brand new caliber, jointly developed by CCI-Speer and Glock. The .45 GAP uses a slightly rebated rim case, meaning the extractor rim has a slightly smaller diameter than the outside diameter of the case. Again, this allows the .45-caliber case to be extracted and ejected from a pistol originally designed for the 9mm. The internal dimensions of the .45 GAP case are significantly different from the .45 Auto case. The internal case wall profile allows the .45-caliber bullets to be deeply seated without bulging the case.

The web of the .45 GAP case (near the primer and rim) is much thicker than a .45 Auto case. This allows the .45 GAP to safely operate at .45 Auto +P chamber pressures. The .45 Auto has a maximum average chamber pressure of 21,000 psi. The .45 GAP and the .45 Auto +P both have maximum pressures of 23,000 psi. The 9mm and .40 S&W both have a 35,000 psi limit. The higher chamber pressure of the .45 GAP allows the 4.5-inch Glock 37 to equal the velocity, energy and momentum of a .45 Auto fired from a five-inch barrel.

The .45 GAP does not use a trimmed .45 ACP case. The .45 GAP case is special and unique. The .45 GAP cartridge uses a .775-inch long case. In comparison, the 9mm case measures .754-inch while the .40 S&W uses a .850-inch case. The .45 Auto case measures .898-inch, which is significantly longer than the .45 GAP case.

The overall cartridge length of the .45 GAP is 1.070 inches. This is much shorter than the 9mm (.168), .40 S&W (1.135) and .45 Auto (1.275). This shorter overall length allows the .45 GAP to fit in 9mm and .40 S&W size magazines. This also permits a variety of bullet shapes and ogive profiles with reliable feed and cycling.

The .45 GAP uses a small pistol primer, while the .45 Auto uses a large pistol primer. The smaller diameter primer puts more distance from the outside diameter of the case to the primer, thus more distance between the primer and the breech / action elements in the 9mm frame pistol. Remember, the 9mm Glock 17 was introduced five years before the .40 S&W caliber was developed.

Glock 37

Like all Glock pistols, the Glock 37 has a hammer-forged barrel, Tenifer corrosion-resistant treatment and polymer frame. Like all Glocks, the Glock 37 has three safeties: trigger safety, firing pin safety and drop safety. Like the vast majority of Glocks, the Glock 37 comes with a 5.5-pound connector, which translates to about an eight-pound trigger pull. All Glocks are “constant double action,” which is essentially double action only.

The Glock 37 uses a double-pinned locking block like the .40-caliber Glocks. Like all Glocks, the Model 37 has a finger groove front and checkered rear grip panel. Like all standard and compact GAPs, the Model 37 has a front accessory rail.

Compared to the .40-caliber Glock 22, the .45-caliber Glock 37 has the same 4.5-inch barrel, the same 1.18-inch grip width, the same overall height and length, and the same sight radius. The .40-caliber GAP has a 1:9.8-inch twist rate with hexagonal rifling. The .45-caliber GAP has a 1:15.8-inch twist rate with octagonal rifling.

The slide on the Glock 37 measures 1.13 inches, is slightly wider than the grip panel, and is heavily beveled at the front and along the bottom to blend with the frame. The slide on the Glock 22, at 1.01 inches, is narrower than the grip panels. This one-eighth-inch difference in slide width prevents the Glock 37 from using most holsters designed for the 9mm Glock 17 and .40 S&W Glock 22.

Until holsters are specifically developed for the standard frame Glock 37, holsters for the large frame Glock 20 and Glock 21 will work. The slide on the standard frame Glock 37 is virtually identical to the large frame Glock 21, just beveled and one-fourth-inch shorter. Magazine holders for the Glock 17 and Glock 22, however, will accept the Glock 37 magazines. The Glock 37 holds 10 rounds in a staggered magazine. At the October 2003 IACP convention, Uncle Mike’s announced several paddle, hip, vertical, horizontal and undercover holsters that fit the Glock 37.

45 GAP Ammo

For the record, .45 Auto ammo cannot be used in the .45 GAP-caliber pistol. The .45 Auto ammo will fit in the chamber but the slide will not go all the way forward into battery. The .45 GAP magazine will not accept .45 ACP ammo. The top round can be inserted, but the magazine is too short to accept additional rounds. Vice versa is also true.

The .45 GAP ammo should not be fired from a .45 Auto pistol. These cartridges all headspace on the case mouth. The shorter .45 GAP cartridge is not properly headspaced by the .45 Auto chamber even if the extractor holds it to the breech face tight enough to fire the round.

Much of the early velocity figures were (oddly) based on a four-inch barrel. The Glock 37 has a 4.5-inch barrel. From our test gun, we got 1055 fps from the CCI-Speer 185-grain Gold Dot and 983 fps from its 200-grain Gold Dot. That is 457 ft-lbs and 429 ft-lbs of energy, respectively. In comparison, the .40 S&W 155-grain JHPs have around 500 ft-lbs, while the .40 S&W 180-grain JHPs have about 360 ft-lbs when fired from a 4.5-inch Glock 22.

Gold Dot bullets have an electroplated copper jacket, not a mechanically wrapped jacket. As a result, the bonded jacket will not separate from the core, even after an angular impact with auto glass. For training and practice, the same bullet weights and same bullet profiles are available in the lower-cost Lawman line. This 185- and 200-grain ammo uses Totally Metal Jacketed (TMJ) bullets with no exposed lead.

The CCI-Speer 185-grain Gold Dot penetrates 10.6 inches of bare gelatin, meeting the U.S. Border Patrol requirements for minimum penetration. The CCI-Speer 200-grain Gold Dot penetrates 12.3 inches of bare gelatin, meeting the FBI requirements. After heavy clothes, these police loads penetrate 12.1 to 14.4 inches (185-grain) and 13.5 to 15.8 inches (200-grain).

The 185-grain Gold Dot expands to .81-inch in bare gelatin and an average of .72-inch in gelatin after heavy clothes. The 200-grain Gold Dot expands to .77-inch in bare gelatin and to .70-inch after heavy clothes.

Shooting Impressions

We put 400 rounds of CCI-Speer ammo through the Glock 37 test pistol, equally divided into 185-grain, 200-grain, Gold Dot and Lawman TMJ loads. Some was fired during quarterly qualifying at night, against scored targets. At 50 yards, the Gold Dot HP and Lawman TMJ bullets of the same weight have the same point of impact. The Glock 37 fed, chambered, fired, extracted and ejected without any problems.

Compared to the .40-caliber Glock 22, the .45-caliber Glock 37 feels more top-heavy, which helps pointability and recoil recovery. The felt-recoil from the Glock 37 with 200-grain loads was similar to the Glock 22 firing ballistically similar 180-grain loads.

The empty, .40-caliber Glock 22 weighs about 23 ounces, compared to 26 ounces for the empty, .45-caliber Glock 37. However, when fully loaded (10 rounds of .45 GAP and 15 rounds of .40 S&W) the two pistols have the identical 34.5-ounce weight. With both the .40-caliber Glock 22 and .45-caliber Glock 37 shooting CCI-Speer Gold Dots, the accuracy at 25 yards was the same.

Technically, the 200-grain .45 GAP has a Power Factor (recoil) of 197. The 180-grain .40 S&W has a Power Factor of 182. In equal weight guns, which the loaded Glock 22 and Glock 37 are, this means the .45 GAP “kicks” about eight percent more.

Predictions? The Glock 37 will seriously challenge all of the large frame, .45-caliber autos, both polymer and steel frame. The Glock 37 will also join the wide array of .40 S&W and .357 SIG pistols for police departments wanting to improve on the marginal 9mm caliber.

Those are easy predictions. Will the .45 GAP replace the .40 S&W as American’s Police Caliber? Probably not. But it will push the .45 Auto into further oblivion. And the .45 GAP will give those tossed between the .40 S&W and .357 SIG a credible third choice.

Ed Sanow is the editorial director of LAW and ORDER and may be reached at


Winchester’s New 45 GAP Ammo

In 1905, the 45 ACP caliber and the Colt pistol were presented to the military trials. The big-bore cartridge pushed a 200-grain bullet to 900 fps. The Army’s response? Great caliber, but the bullet is too light. In 1911, the 45 ACP caliber was officially released with the reworked Colt Government Model. The new cartridge pushed a 230-grain bullet between 790 and 830 fps. And the rest is military, police and stopping power history.

The reputation of the 45 ACP was so solidly built around 230-grain bullets that for virtually all hardcore handgunners, “45-caliber” literally equals “230 grains.” And so it is, as the 45 GAP tries to breathe new life into the old but legendary 45 ACP caliber. The officer who wants a 45-caliber duty pistol (and nothing else will do) also wants a 230-grain JHP (and nothing else will do here, either).

The Glock 37 in 45 GAP was co-developed with CCI-Speer based on 185- and 200-grain ammo. However, Winchester just launched an entire line of 45 GAP ammo behind a 230-grain Ranger SXT flagship. According to Winchester, the use of a 230-grain bullet in the short 45 GAP case is a powder selection issue, not a case dimension issue.

No new police caliber can last long without both duty and training ammo. Winchester has six 45 GAP offerings: 1) the 230-grain Ranger SXT hollowpoint; 2) the 185-grain Silvertip hollowpoint; 3) the 230-grain standard JHP; 4) the 230-grain FMJ hardball; 5) the 230-grain WinClean Brass Enclosed Base; and 6) the 175-grain Frangible. 

In ordnance gelatin, the 230-grain Ranger SXT expands to .75-caliber and penetrates 11.6 inches (bare) and 12.3 inches (heavy clothes). The 185-grain Silvertip also expands to .75-caliber and penetrates 11.1 inches (bare) and 13.7 inches (heavy clothes).

At the November 2003 SWAT Round-up in Florida, 3,000 rounds of Winchester’s 45 GAP 230 grain ammo were cycled through each of three different Glock 37 pistols… flawlessly. As a result, the Orange County, FL, Sheriff’s Department, host of the annual SWAT Round-up, may just become the first major law enforcement agency to adopt the Glock 37. 

With these 230-grain loads, the 45 GAP really is fully equal to the legendary 45 ACP, except in a standard frame pistol.

Published in Law and Order, Jan 2004

Rating : Not Yet Rated

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