The .45 GAP

By Chuck Hawks

2003 saw the introduction of the first pistol cartridge to bear the Glock name. It is called the ".45 Glock Automatic Pistol." The .45 GAP cartridge came about due to requests from American police departments for a .45 caliber cartridge in a pistol with a medium size (9mm) grip frame.

Earlier requests for a big bore pistol with a 9mm-size grip had resulted in the development of the .40 S&W cartridge. The new .45 GAP extends the concept to its logical conclusion.

The relaxation or elimination of size and strength requirements for police officers has resulted in the hiring of both male and female officers with hands too small to comfortably handle large frame .45 ACP pistols with traditional size grips. Hence the call for a medium frame .45 pistol. Glock, the largest supplier of pistols to U.S. police agencies, partnered with Speer to give the boys and girls in blue what they wanted.

The initial .45 GAP pistol was based on Glock's full size, medium frame, Model G22 with a modified slide. This became the Model G37 pistol.

The new cartridge is a unique creation, based on no existing case. In form it is a typical rimless, straight wall, pistol case similar in length to the 9x19mm. Headspacing is on the case mouth, as with majority of auto pistol cartridges. It has a slightly rebated rim diameter of .465", a case length of .755" and a cartridge overall length of 1.07". The new case uses a small pistol primer (CCI #500). Bullet diameter is .452", the same as the .45 ACP. The .45 GAP is not interchangeable with the .45 ACP and its cases cannot be formed from .45 ACP brass. The SAAMI maximum average pressure limit for the new cartridge is 23,000 psi.

The .45 GAP was actually designed for bullets weighing 200 grains or less, although demand for loads using 230 grain bullets quickly developed and that bullet weight was added to the factory loading lists. The .45 GAP manages to equal the ballistic performance of standard .45 ACP factory loads, even though it is based on a smaller case. This minor ballistic miracle is achieved by using advanced propellant powders and loading the .45 GAP to 2,000 psi higher pressure.

Speer .45 GAP factory loads include Gold Dot 185 grain JHP and Lawman 185 grain TMJ bullets at a muzzle velocity (MV) of 1020 fps and muzzle energy (ME) of 427 ft. lbs. At 50 yards the velocity of the 185 grain Gold Dot bullet (BC .109, SD .130) is 937 fps and the energy is 361 ft. lbs.; at 100 yards the velocity is 873 fps and the remaining energy is 313 ft. lbs. The 100 yard mid-range trajectory is +4.3".

Speer also offers factory loads with 200 grain Gold Dot JHP and Lawman 200 grain TMJ bullets at a MV of 950 fps and ME of 401 ft. lbs. At 50 yards the velocity of the 200 grain Gold Dot bullet (BC .138, SD .140) is 896 fps and the energy is 356 ft. lbs. At 100 yards the velocity is 850 fps and the remaining energy is 321 ft. lbs. The 100 yard mid-range trajectory is +4.7".

Federal Cartridge, owned by ATK (the parent company of both Speer and Federal), offers a premium Personal Defense loads using a 185 grain Hydra-Shok bullet at 1090 fps and a 230 Hydra-Shok at 880 fps. Federal also has an American Eagle economy loads using 185 grain and 230 grain FMJ bullets at 1090 and 880 fps respectively. These .45 GAP ballistics are achieved in a 5" test barrel.

Remington offers a single .45 GAP load, a 230 grain Metal Case bullet (FMJ) at 880 fps, which is 45 fps faster than they load the same bullet in .45 ACP. Both Remington loads are chronographed in 5" barrels.

Winchester catalogs four .45 GAP factory loads. These include a 185 grain Silvertip JHP at 1000 fps, 230 grain WinClean (BEB) bullet at 875 fps, 230 grain FMJ bullet at 850 fps and 230 grain JHP bullet at 880 fps. Like Remington, Winchester uses a 5" barrel for testing.

These are the same bullets used in .45 ACP factory loads. Their terminal performance (expansion and penetration) remains the same whether fired from .45 GAP or .45 ACP pistols. Accuracy from the G37 should be virtually identical to the accuracy of the same bullets fired in a Glock G21 (.45 ACP) service pistol.

Here is some reloading data courtesy of the Hodgdon Powder Company:

  • Starting Load: 185 GR. Hornady XTP bullet, 8.0 grains HS-6 powder, MV 890 fps, 17,700 psi.
  • Maximum Load: 185 GR. Hornady XTP bullet, 9.0 grains HS-6 powder, MV 1017 fps, 22,500 psi.

These loads were developed using Speer cases, Winchester SP primers and tested in a 5" barrel.

The recoil of the new cartridge is comparable to that of .40 S&W or .45 ACP pistols of similar weight firing bullets of approximately the same weight at equal velocities. There is no free lunch in the real world of physics.

In its first decade, the .45 GAP has carved a niche for itself, but failed to surpass either the .40 S&W or .45 ACP service pistol cartridges in popularity with police or civilians. All of the major American ammunition companies, except Hornady, offer .45 GAP factory loads, so ammunition is reasonably available in the U.S. People with small hands who prefer a .45 caliber bullet to a .40 caliber bullet are well served by the .45 GAP in a medium frame pistol.

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Copyright 2003, 2014 by Chuck Hawks. All rights reserved.