The 280 Ackley Improved is a centerfire rifle cartridge standardised by SAAMI in ANSI/SAAMI Z299.4. SAAMI sets its maximum average pressure at 65,000 psi, and measures its reference velocities in a 24.000 in standard test barrel rifled 1 turn in 9.00 in. This guide sets out SAAMI’s published reference velocity for each bullet weight, computes the muzzle energy each one carries, and compares the 280 Ackley Improved with the 280 Remington on the same basis.
280 AI 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 |
|---|---|---|
| 140 gr | 3,260 fps | 3,303 ft-lb |
| 155 gr | 2,930 fps | 2,954 ft-lb |
| 168 gr | 2,830 fps | 2,987 ft-lb |
What the numbers mean for a shot
SAAMI lists 3 reference bullet weights for the 280 Ackley Improved, from 140 to 168 grains. The lightest, 140 grains, is listed at 3,260 fps, which computes to 3,303 ft-lb. The heaviest, 168 grains, is listed at 2,830 fps, which computes to 2,987 ft-lb.
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 280 AI ammo range lists whatever its maker publishes for that item.
Twist rate, chamber and pressure
SAAMI’s standard test barrel for the 280 Ackley Improved is 24.000 in long and rifled 1 turn in 9.00 in, with a .2837 in groove diameter. That is the barrel every reference velocity above was measured in, not a statement about your rifle: a shorter production barrel will usually give lower velocity, and a twist slower than a bullet needs will not stabilise it. The maximum average pressure is 65,000 psi. Fire 280 Ackley Improved 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.
280 AI vs 280: 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 | 280 Ackley Improved | 280 Remington |
|---|---|---|
| Maximum average pressure | 65,000 psi | 60,000 psi |
| Standard test barrel length | 24.000 in | 24.000 in |
| Test barrel twist rate | 1 turn in 9.00 in | 1 turn in 10.00 in |
| Test barrel groove diameter | .2837 in | .2837 in |
| Lightest reference load | 140 gr — 3,260 fps / 3,303 ft-lb | 120 gr — 3,135 fps / 2,618 ft-lb |
| A weight both list | 140 gr — 3,260 fps / 3,303 ft-lb | 140 gr — 2,985 fps / 2,769 ft-lb |
| Heaviest reference load | 168 gr — 2,830 fps / 2,987 ft-lb | 165 gr — 2,800 fps / 2,872 ft-lb |
SAAMI standardises the 280 Ackley Improved at 65,000 psi and the 280 Remington at 60,000 psi, so the 280 Ackley Improved runs 5,000 psi higher. At 140 grains, a weight both list, SAAMI’s 280 Ackley Improved reference velocity is 3,260 fps (3,303 ft-lb computed), against 2,985 fps (2,769 ft-lb) for the 280 Remington. On that row the 280 Ackley Improved carries the more energy. Their standard test barrels differ (24.000 in, 1 turn in 9.00 in for the 280 Ackley Improved; 24.000 in, 1 turn in 10.00 in for the 280 Remington), so compare the reference rows with that in mind.
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: 280 ammo.
280 AI ballistics questions
What is the maximum pressure of the 280 Ackley Improved?
ANSI/SAAMI Z299.4 sets the maximum average pressure for the 280 Ackley Improved at 65,000 psi.
What twist rate and barrel length does SAAMI use for the 280 Ackley Improved?
SAAMI’s standard test barrel for the 280 Ackley Improved is 24.000 in long and rifled 1 turn in 9.00 in. Your own rifle may differ.
What bullet weights does SAAMI list for the 280 Ackley Improved?
SAAMI lists 3 reference weights, from 140 to 168 grains: 140, 155 and 168.
Is the 280 Ackley Improved more powerful than the 280 Remington?
Power is not a SAAMI measure, but reference muzzle energy is a fair proxy. At 140 grains, a weight both list, SAAMI’s 280 Ackley Improved reference velocity is 3,260 fps (3,303 ft-lb computed), against 2,985 fps (2,769 ft-lb) for the 280 Remington.
What is the effective range of the 280 Ackley Improved?
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 280 Ackley Improved drop at 300 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 280 AI ammunition from Nosler, Federal, Weatherby, Barnes and Hornady. Browse the full 280 AI ammo range.
