Glock 37

The Glock 37 is Glock’s full-size .45 GAP (Glock Auto Pistol) pistol — a service-size .45-caliber handgun built around the .45 GAP cartridge that Glock developed jointly with Speer in 2003 specifically for the Glock platform. The .45 GAP delivers .45 ACP-class terminal performance in a shorter cartridge that fits service-pistol frames without the grip enlargement .45 ACP requires. The Glock 37 carries 10+1 in standard magazines. Impact Guns carries the Glock 37.

Read our full Glock 37 Buying Guide ↓

What .45 GAP Is and Why It Exists

.45 GAP is a shorter .45-caliber cartridge developed in 2003 to deliver .45 ACP terminal performance from a service-pistol frame the size of a 9mm or .40 S&W gun. The .45 ACP cartridge is long enough that pistols chambered for it require larger grips than 9mm pistols — uncomfortable for smaller-handed shooters and bulky for concealed carry. .45 GAP solved that by shortening the case while maintaining .45-caliber bullet performance at slightly reduced velocity. The result: a Glock 37 fits the same hand as a Glock 17, with .45-caliber terminal effect.

The Glock 37 in Service

Several U.S. law enforcement agencies adopted the Glock 37 and the .45 GAP family in the mid-2000s — New York State Police, Georgia State Patrol, and others issued G37s as standard sidearms. The cartridge proved capable in service use; agencies that adopted it generally reported satisfactory performance. .45 GAP has since lost market momentum as 9mm hollow point ammunition advanced and shooters returned to 9mm capacity advantages, but the Glock 37 remains in production for shooters committed to the platform.

Why Buy a Glock 37 Today

For shooters who specifically want .45-caliber terminal performance in a service-frame pistol that fits average hands comfortably, the Glock 37 remains the only mainstream option. The platform’s small but loyal following includes shooters who experienced the cartridge in agency service, shooters with smaller hands who can’t comfortably grip .45 ACP pistols, and shooters who value the unique cartridge for what it is. Glock continues to produce .45 GAP pistols and magazines, and Speer/Federal continues to manufacture ammunition.

Ammunition Availability

.45 GAP ammunition is the platform’s practical limitation — available, but not on every shelf the way 9mm or .45 ACP are. Federal, Speer, and a handful of other manufacturers produce .45 GAP in defensive and practice loadings. Buying ammunition in bulk when available is the standard practice. For shooters considering a .45 GAP pistol, ammunition availability should factor into the decision — if reliable supply matters more than the cartridge’s specific advantages, .45 ACP or 9mm may suit better.

Glock 37 vs. Glock 21 vs. Glock 17

The Glock 21 is the full-size .45 ACP Glock — full .45 ACP performance, but in a frame too large for many shooters’ comfortable grip. The Glock 17 is the full-size 9mm Glock — comfortable service-pistol grip with higher capacity but smaller bullet. The Glock 37 splits the difference: G17-sized frame, .45-caliber bullet, 10+1 capacity. The choice depends on what you prioritize: G21 for traditional .45 ACP, G17 for capacity and 9mm logistics, G37 for .45 caliber in a service-size frame.

Frequently Asked Questions

Is .45 GAP the same as .45 ACP?
No — .45 GAP is a different cartridge with shorter case length, lower powder capacity, and ballistic performance close to but not identical to .45 ACP. The two are not interchangeable in firearms; .45 ACP pistols cannot fire .45 GAP and vice versa. Bullet diameter is identical (.451 inch), but case dimensions and chamber specs differ.

Is .45 GAP ammunition still available?
Yes — Federal, Speer, and a handful of other manufacturers continue producing .45 GAP in defensive and practice loads. Availability is more limited than .45 ACP or 9mm; shooters who own .45 GAP pistols typically buy ammunition in bulk when available. Online suppliers are often the best source.

Why don’t more shooters use .45 GAP?
.45 GAP launched in 2003 just as 9mm hollow point ammunition was advancing significantly — modern 9mm defensive loads erased much of the terminal performance advantage .45 caliber traditionally held. The .45 GAP cartridge succeeded technically but lost market momentum as shooters returned to 9mm capacity advantages. Today it occupies a specific niche rather than the mainstream role its developers envisioned.