The 45 Glock Automatic Pistol is a centerfire handgun cartridge standardised by SAAMI in ANSI/SAAMI Z299.3. SAAMI sets its maximum average pressure at 23,000 psi, and measures its reference velocities in a 5.000 in standard test barrel rifled 1 turn in 16.00 in, left hand. This guide sets out SAAMI’s published reference velocity for each bullet weight, computes the muzzle energy each one carries, and compares the 45 Glock Automatic Pistol with the 45 Automatic on the same basis.
45 GAP ballistics chart: SAAMI reference data
SAAMI publishes one nominal mean instrumental velocity for each reference bullet weight, measured at 15 feet from the standard test barrel. It does not publish energy, so the ft-lb column is computed. Where SAAMI lists more than one velocity for a weight, both ends of the span are shown.
Scroll the table sideways for the remaining columns.
| Bullet weight | Reference velocity | Computed muzzle energy |
|---|---|---|
| 175 gr | 995 fps | 385 ft-lb |
| 185 gr | 995–1,090 fps | 407–488 ft-lb |
| 200 gr | 1,020 fps | 462 ft-lb |
| 230 gr | 830–870 fps | 352–386 ft-lb |
What the numbers mean for a shot
SAAMI lists 4 reference bullet weights for the 45 Glock Automatic Pistol, from 175 to 230 grains. The lightest, 175 grains, is listed at 995 fps, which computes to 385 ft-lb. The heaviest, 230 grains, is listed at 830–870 fps, which computes to 352–386 ft-lb. The most energetic reference load is the 185-grain at 1,090 fps: 488 ft-lb computed.
SAAMI lists more than one reference velocity for 185 and 230 grains. Its own note says this is because a weight can carry several introductions meeting different market needs, such as reduced-recoil loads, or because propellant and loading advances allowed higher velocities after the original load appeared.
None of this is a downrange figure. SAAMI measures at 15 feet, so retained velocity, energy and drop depend on the bullet’s ballistic coefficient, which SAAMI does not publish. Each product in our 45 GAP ammo range lists whatever its maker publishes for that item.
Barrel, chamber and pressure
SAAMI’s standard test barrel for the 45 Glock Automatic Pistol is 5.000 in long and rifled 1 turn in 16.00 in, left hand, with a .450 in groove diameter. That is the barrel every reference velocity above was measured in, not a statement about your handgun: handgun barrels vary widely in length, and a shorter barrel gives lower velocity. The maximum average pressure is 23,000 psi. Fire 45 Glock Automatic Pistol ammunition only in a firearm chambered for it. Several unrelated cartridges share a number, so match the full designation on the box to the marking on your barrel.
The 45 Glock Automatic Pistol and the 45 Automatic are separate SAAMI cartridges, standardised at 23,000 psi and 21,000 psi. They are not interchangeable: fire each only in a firearm marked for it.
45 GAP vs 45 ACP: the SAAMI comparison
A figure from one maker’s catalogue cannot be laid beside a figure from another’s: each picks its own test barrel, zero and bullet, and many publish no test barrel at all. SAAMI is the shared basis, because it fixes one standard test barrel and one way of measuring velocity for every cartridge it lists.
Scroll the table sideways for the remaining columns.
| SAAMI specification | 45 Glock Automatic Pistol | 45 Automatic |
|---|---|---|
| Maximum average pressure | 23,000 psi | 21,000 psi |
| Maximum average pressure, +P | No +P standard | 23,000 psi |
| Standard test barrel length | 5.000 in | 5.000 in |
| Test barrel twist rate | 1 turn in 16.00 in, left hand | 1 turn in 16.00 in, left hand |
| Test barrel groove diameter | .450 in | .450 in |
| Lightest reference load | 175 gr — 995 fps / 385 ft-lb | 120 gr — 1,200 fps / 384 ft-lb |
| A weight both list | 200 gr — 1,020 fps / 462 ft-lb | 200 gr — 885 fps / 348 ft-lb |
| Heaviest reference load | 230 gr — 830–870 fps / 352–386 ft-lb | 230 gr — 830–915 fps / 352–427 ft-lb |
SAAMI standardises the 45 Glock Automatic Pistol at 23,000 psi and the 45 Automatic at 21,000 psi, so the 45 Glock Automatic Pistol runs 2,000 psi higher. At 200 grains, a weight both list, SAAMI’s 45 Glock Automatic Pistol reference velocity is 1,020 fps (462 ft-lb computed), against 885 fps (348 ft-lb) for the 45 Automatic. On that row the 45 Glock Automatic Pistol carries the more energy.
What SAAMI cannot settle is anything past the muzzle. It publishes no ballistic coefficients and no downrange data, so it cannot say which cartridge shoots flatter at distance; that depends on the bullet. We stock the other side of this comparison too: 45 ACP ammo.
45 GAP ballistics questions
What is the maximum pressure of the 45 Glock Automatic Pistol?
ANSI/SAAMI Z299.3 sets the maximum average pressure for the 45 Glock Automatic Pistol at 23,000 psi.
What twist rate and barrel length does SAAMI use for the 45 Glock Automatic Pistol?
SAAMI’s standard test barrel for the 45 Glock Automatic Pistol is 5.000 in long and rifled 1 turn in 16.00 in, left hand. Your own handgun may differ.
What bullet weights does SAAMI list for the 45 Glock Automatic Pistol?
SAAMI lists 4 reference weights, from 175 to 230 grains: 175, 185, 200 and 230.
Is the 45 Glock Automatic Pistol more powerful than the 45 Automatic?
Power is not a SAAMI measure, but reference muzzle energy is a fair proxy. At 200 grains, a weight both list, SAAMI’s 45 Glock Automatic Pistol reference velocity is 1,020 fps (462 ft-lb computed), against 885 fps (348 ft-lb) for the 45 Automatic.
What is the effective range of the 45 Glock Automatic Pistol?
Effective range is not a SAAMI specification and it is not a measured figure. SAAMI measures velocity at 15 feet, so it says nothing about performance at distance; that depends on the bullet and the shooter.
How much does the 45 Glock Automatic Pistol drop at 100 yards?
SAAMI publishes muzzle velocity only, so it cannot give a drop figure. Drop depends on the bullet’s ballistic coefficient and on the zero range. A drop figure is unusable without its zero, so use the figure a maker prints for the specific load.
Where to buy these loads
Hilltop Armory carries 45 GAP ammunition from Buffalo Bore, Copper Only Projectiles (C.O.P.), Magtech, Sellier And Bellot and Speer. Browse the full 45 GAP ammo range.
