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Glock 38 and 39 Pistols…the .45 GAP

The trend of adopting semiautomatic pistols to replace the traditional service revolver, when it began to gain momentum in the early 1980s, focused on high capacity 9mm handguns. This was largely because the initial impetus for change had been the perception that officers armed with “six-shooters” were on the losing end of a firepower race against criminals armed with high capacity autoloading weapons.

However, experience showed that certain types of 9mm ammunition did not always have the quick, decisive fight-stopping effect that law enforcement’s collective institutional memory had long associated with .357 Magnum revolvers and .45 ACP caliber semiautomatic pistols. A number of working officers and department firearms instructors pushed for .45 ACP pistols, and many departments adopted or approved them.

Being both wide and relatively long, the .45 ACP (Automatic Colt Pistol) cartridge had demanded one of two accommodations. The traditional concession had been a single-stack magazine, which kept grip frame dimensions within reasonable limits but cut the magazine capacity to seven or eight rounds. This was seen in Colt, HK P9, SIG, and Smith & Wesson duty pistols.

The other accommodation was a “wide-body” grip frame, which took a higher capacity double stack magazine, compromising the ability of an officer with short fingers to properly grasp and master the handgun. This was seen in the .45 ACP duty weapons offered by Beretta in its Model 8045, Glock, Heckler and Koch in the HK USP, and some other manufacturers.

In 1990, Smith & Wesson and Winchester had brought forth the .40 S&W cartridge, a 10mm round shortened to the length of the 9mm Luger cartridge and adaptable to trimmer grip frame platforms with minimum sacrifice in round count. In the popular S&W pistol, the Model 4006 held 12 .40 caliber rounds, exactly between the 16 rounds of a typical 9mm and the eight rounds of a typical .45. This apparently ideal compromise quickly made the .40 S&W cartridge the most popular among American law enforcement agencies buying new duty handguns.

While the compromise has worked well for the most part, there are still a significant number of police departments and individual officers who 1) prefer the terminal ballistics characteristics of .45 caliber ammunition; 2) want a .45 with more than the traditional eight or nine rounds of a single-stack; and 3) still require a grip frame of manageable girth and trigger reach for small-handed officers.

Seeing this demand, Glock joined with CCI/Speer to create a shorter .45-caliber autopistol cartridge that could still duplicate the ballistics of the .45 ACP. A team led by Speer engineer Ernest Durham created the .45 GAP (Glock Auto Pistol) cartridge.

Though it did not reach into the power range of +P pressure .45 ACP ammunition as issued by such departments as the Denver, CO Police or the San Bernardino County, CA Sheriff’s Office, it quickly became apparent that the .45 GAP equaled or slightly exceeded the ballistics of the standard pressure ammunition used by most law enforcement agencies that have issued or authorized .45 ACP handguns.

The first platform for the .45 GAP cartridge was the Glock 37 pistol, introduced in 2003. It has proved to be the most popular in its caliber, though other manufacturers such as Springfield Armory and ParaOrdnance, have chambered pistols for the .45 GAP. The G37 has a frame identical in dimension with the 9mm Glock 17, the .40 S&W Glock 22, and the Glock 31 chambered for .357 SIG. The G37’s slide is slightly wider, however. Glock 37 magazines will fit in pouches designed for 9mm, .40, or .357 Glock magazines.

Glock’s Compact Model 38

As interest in the .45 GAP service pistol began to increase, so did demand for smaller models. The standard Glock 37 has a full-length grip frame and a 4.5-inch barrel with slide of commensurate length. A great many departments have adopted or approved compact versions of full-size Glocks for their personnel operating in plainclothes, administrative uniforms, and of course, off duty.

Some departments have determined that the compact Glock is large enough for duty uniform wear, yet small enough for plainclothes carry, and have thus adopted the compact as standard for all personnel no matter what their assignment.

The Boston Police issues the compact, 13-plus-one round Glock 23 compact in caliber .40 S&W to all armed personnel. The New York Police Department authorizes the 15-plus-one shot Glock 19 compact in 9mm for both uniformed and plainclothes officers, and it has proved to be the single most popular service pistol among the 30,000-plus NYPD officers, who buy their own duty weapons from an approved list.

Introduced in 2005, the Glock 38 is the compact version of the service size Glock 37 in caliber .45 GAP. A shorter grip frame brings cartridge capacity down from the 10-plus-one in the G37 to eight-plus-one in the G38, and the barrel is shortened from 4.5 inches to 4.0 inches in length. The Glock 38 is directly analogous in size (except, of course, for the slightly wider slide) to the Glock 19 9mm, the Glock 23 .40 caliber, and the Glock 32 in .357 SIG.

Glock’s Subcompact Model 39

After the success of their compact models in law enforcement, beginning with the Glock 19 9mm in the late 1980s, Glock engineered even smaller “subcompact” pistols. Introduced in the mid-1990s, the radically shortened grip-frames of the Glock subcompacts allow 10-plus-one cartridge capacity in the 9mm Glock 26, and nine-plus-one in the .40 S&W caliber Glock 27 and the .357 SIG caliber Glock 33. The barrel length is only 3.5 inches. These pistols have received warm acceptance in law enforcement.

The subcompact analog in the .45 GAP line is the Glock 39. The much shorter grip frame allows a six-plus-one capacity of the large diameter .45 GAP cartridges. Like other subcompact Glocks, it differs from larger models in that it uses a double captive recoil spring. While requiring a firm grasp to activate the slide, this feature also absorbs a good deal of the pistol’s recoil, making the subcompact Glocks in all calibers lighter in recoil than one would expect.

Extremely popular for off-duty carry, the “baby Glocks” have also become popular as backup weapons. The Dayton, OH Police issue a baby Glock to each officer as a backup handgun. Shortly after adopting the Glock 22 service pistol for its troopers, the Georgia State Patrol issued each of them a Glock 27 and ankle holster for backup. The Kentucky State Police for many years issued a Walther .380 ACP as backup to each trooper’s S&W Model 1006 10mm. KSP switched to the Glock 27 as an issue backup, and subsequently adopted the 5.3-inch barrel Glock 35 Tactical/Practical as the primary duty sidearm.

Whichever pistol is adopted first, a “baby Glock” that matches the duty Glock allows the officer to use his or her duty magazines to reload the backup weapon if necessary. The G39 allows this valuable tactical option when the .45 GAP is adopted.

Accuracy Testing

The Glock pistols chambered for the GAP round meet all reasonable service pistol accuracy specifications. This proves to be true of the compact and subcompact versions as well. Two training loads and one service load were selected, representing three of the primary law enforcement ammunition manufacturers, and also encompassing the three available bullet weights for .45 GAP in both duty and training formats.

Testing protocol involved five-shot groups fired hand-held from an MTM bench rest at a distance of 25 yards. Groups were measured between the centers of the farthest-apart bullet holes. The overall five-shot group measurement was taken as an indication of the handgun’s deliverable accuracy when braced and fired by an officer not impaired by life-threatening stress.

Then, the best three hits within the group were measured also. Time and experience have taught the testing team that this second measurement factors out enough unnoticed human error to give a very close approximation of what the same handgun/ammunition combination can do for all five shots when fired from a machine rest.

The Glock 38 Compact put five rounds of Federal American Eagle 185 grain full metal jacket training ammunition into 2.15 inches. The best three of those hits were in a group measuring only 1.15 inches. With Speer Gold Dot 200 grain bonded hollow point duty loads, the G38 delivered a five-shot group measuring 1.75 inches. The best three of those hits formed a group measuring just under one inch at 0.95 inches. This proved to be the most accurate load in the test G38 pistol.

Winchester USA brand 230 grain round nose full metal jacket training ammo printed a five-shot group from the G38 that measured 2.35 inches. The “best three” group tied the American Eagle with the lighter, flat point bullet, at 1.15 inches.

The same three loads were then tested in the subcompact Glock 39 pistol. The American Eagle 185 grain flat point training round exhibited “4+1” syndrome. That is, it sent its first hand-chambered shot to a slightly different point of impact vis-à-vis point of aim than subsequent automatically cycled rounds. The five shot group measured 4.65 inches, but the subsequent four shots were in a 2.70-inch group, and the best three hits were in a 2.40-inch cluster.
With the Speer Gold Dot 200 grain BHP duty load, we saw the same phenomenon. The first hand-cycled shot opened the G39’s total five shot group to 4.30 inches. However, the next four autoloaded cartridges sent their bullets into a tight 1.65-inch cluster, and the best three of those hits were only 1.05 inches apart.

The “4+1” effect was present with all three loads tested in the G39, including the round nose Winchester 230 grain .45 GAP training ammunition. Counting the first shot, the five-shot group measured 3.90 inches, more than doubling what would have been an excellent group, judging by the fact that the next four shots hit only 1.90 inches apart. The best three shots went under an inch, forming a group of 0.95 inches.

In summary, both pistols showed high accuracy potential and are ample in that respect for law enforcement use. Even the errant first shots from the Glock 39 are not damning when taken in context. If a member of the police department pistol team had been shooting the G39 in an off-duty gun match, the farthest shot in each group still would have hit the 10-ring of a B27 police competition target, and merely cost the competing officer one tie-breaking center X ring hit. Against a live human antagonist, the worst hits delivered in the accuracy testing still would have struck “center mass.”


Our test team has collectively sent several thousand .45 GAP rounds downrange in exercises ranging from qualifications to competitions. We have observed no mechanical malfunctions. Human error malfunctions have been minimal, primarily failure to seat a fully loaded magazine with the pistol’s slide forward, and shooters with “straight thumbs” grasp over-riding the slide lock lever and causing it to fail to lock the slide back. In terms of mechanical function, the pistols have proved themselves extraordinarily reliable in all three formats: G37, G38, and G39. These results have been confirmed in testing by other entities of which we are aware.

Small-handed shooters uniformly appreciated the relatively small frames of the G38 and G39 pistols. So, however, did those on the test team with extremely large hands: they felt that with more flesh and bone wrapped around the grip frames, they had more control, and with the shorter trigger reach as compared to .45 ACP Glocks, they could “get more finger on the trigger” for more leverage and trigger control in rapid fire exercises.

All Glock .45 GAP pistols are fitted with the company’s extended slide stop lever. This is because the wider slide on the .45 GAP makes the smaller, standard slide release more difficult to reach. Those shooters who fired with straight thumbs and right handed would occasionally override the slide stop lever with their thumbs, causing a human error-induced failure of the slide to lock back on an empty chamber.

For the power they deliver, both the compact and the subcompact Glock .45 GAPs were unanimously determined to have surprisingly soft recoil and good control. On this, the testing team was unanimous. The Glock 38 recoil is very similar to that of the .40 caliber Glock 23 compact. It “kicks” only a little more than the comparable-size Glock 19 in 9mm.

The Glock 39 is surprisingly soft in its recoil for so small a .45 caliber pistol. Most felt that it was even more controllable than the .40 caliber Glock 27, and distinctly more controllable than the subcompact Glock 33 in .357 SIG. Among analogous “baby Glocks,” only the Glock 26 in the mild 9mm Luger chambering was perceived to have less recoil than the subcompact Glock in .45 GAP.

.45 GAP’s Law Enforcement Track Record

Departments that have tested the .45 GAPs consistently give favorable reports. The Sanford, NC Police adopted the Glock 37 as standard issue for all 79 sworn personnel in May 2005. “We all liked the grip fit better,” reported Captain Kevin Gray, “and scores went up. We’ve had no complaints with the Glock 37. Not one.”

The first SWAT team in the country to adopt the .45 GAP was that of the Fulton County, GA Sheriff’s Department. That agency long has issued the Glock 22 pistol as standard, and still considers that sixteen-shot .40 caliber to be ideal for patrol needs. Its SWAT team determined that for its particular needs, a more powerful pistol in the .45 caliber range was desirable, and adopted the G37 largely because of commonality of previous training with the standard size Glock pistol.

With one shooting incident already with the new gun, says FCSO Lieutenant Richard McLarin, the result was an instant incapacitation of the suspect. The Winchester 230 grain SXT ammunition performed as designed with bullet expansion in the .70 to .75 caliber range.

As of this writing, the Glock GAP series is being seriously considered for adoption by two large state police agencies, and it has just been adopted by a third. It was announced in June 2006 that the Georgia State Patrol would issue a Glock 37 service pistol and a Glock 39 backup pistol to each of its troopers. The GSP previously issued a standard size Glock 22 and a subcompact Glock 27 backup/off-duty gun to all troopers. The Georgia adoption followed extensive testing of .45 GAP handguns.

Disparate Impact Factor

One issue that arises in law enforcement weapon selection that never seems to be addressed in gun magazines is department liability in regard to disparate impact lawsuits by small-handed officers who are issued firearms too large for them to control to a qualification standard. There have been many such lawsuits, and the plaintiff officers have prevailed in most.

Several years ago, one large federal agency paid several million dollars to a group of female agent trainees fired for failure to qualify with firearms deemed too large for their hands. That agency now issues Glock 22 and 23 pistols, caliber .40 S&W, with the same frame size as the .45 GAP series under discussion here. This writer is aware of no disparate impact suits stemming from issue of standard size Glock pistols, which seem to be highly adaptable to small hands.

Therefore, if a department deems a .45 caliber handgun to be its choice as a duty weapon, the Glock series chambered for the .45 GAP cartridge appears to have significant liability advantages for the agency in that it creates a cushion against disparate impact claims.


The Glock has for some time been the dominant service pistol in American police work. One reason has been the availability of the guns in multiple sizes to accommodate the needs of uniform, plainclothes, and backup missions. The addition of the compact Glock 38 and subcompact Glock 39 pistols to this manufacturer’s .45 GAP series greatly enhances versatility if that caliber is chosen or approved by a department.

The expansion of the line to include the G38 and the G39, therefore, makes the .45 GAP a more practical choice than ever before for law enforcement agencies exploring the possibility of adopting larger caliber service pistols.

Massad Ayoob has been a sworn officer for 32 years and is currently serving in a part-time capacity as a captain with the Grantham, NH Police Department. He is director of Lethal Force Institute, and is the author of several weaponry, use-of-force, and self-defense textbooks and training tapes. He can be reached at

Published in Tactical Response, Sep/Oct 2006

Rating : 9.8

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Update on my 45 GAP Glocks

Posted on : Oct 1 at 4:08 PM By J. Dooly

Thought I would update my previous post. I now have number 7 Glock in 45GAP. I have been reloading for 35 yrs now and the 45Gap is one of the, if not the most accurate rounds I have ever loaded. The accuracy is astonishing even when compared to my Gold Cup Match 45 1911's. Hard to believe since it is a striker fired pistol. I do not get quite the accuracy from my other Glocks chambered in various calibers. The Glock 22 and 23 Gen 4 in 40cal are very accurate as well but with my 45GAPs I do not have to concentrate as hard to achieve very good results. I started collecting Glocks in 1988 and have not looked back since. I bought my first Glock Gen 3 mod 37 in I believe late December 2003 and have never looked back. Since then I have picked up several Gen 3 mod 37's and a couple of Gen 4 mod 37's, a mod 38 and a baby glock mod 39. The mod 21 45acp even in the gen 4 is a bit large in my hands so much so I think about it during causal target practice. I gave up shooting my Gen 3 mod 21 as it is just too large a grip for me. It's all about what feels best to the shooter. For those who want .45 power in a full or med sized Glock with a nine-millimeter sized grip frame, the model 37, 38, & 39 chambered in .45 GAP is an excellent option. Ammo is plentiful and always has been on the internet ammo search engines. I use regularly for all my ammo purchases. Price is on pare or less than the 45acp.

question re disparate impact

Posted on : Jun 20 at 2:07 PM By John Larson

Does the author or anyone have any information regarding the disparate impact lawsuits mentioned in this article? Any help is appreciated. The issue is regarding failure to qualify with firearms deemed too large for their hands. Women mandated to use larger/standard size firearms for qualifying for police departments ... Thank you!

Glock 37

Posted on : Jun 18 at 12:42 AM By J. Dooly

Loved the G37 so much that I bought a G38 to go with it. The 45 GAP is a perfect fit for the hands. Cant go wrong with the GAP.


Posted on : Sep 3 at 3:10 PM By JEFF



Posted on : Nov 17 at 12:39 AM By J. Brooks

I've been called a heretic by my dept. range staff for stating that the .45 GAP is basically superior to the .45 ACP. My dept. hasn't and won't approve the GAP since we have three different calibers of duty Glocks already. However, I own a G-37 & I like shooting it more than my three .40 Glocks. Good article.

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