The 270 Winchester Short Magnum 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 10.00 in. This guide sets out SAAMI’s published reference velocity for each bullet weight, computes the muzzle energy each one carries, and compares the 270 Winchester Short Magnum with the 270 Winchester on the same basis.
270 WSM 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 |
|---|---|---|
| 130 gr | 3,275 fps | 3,096 ft-lb |
| 140 gr | 3,125 fps | 3,035 ft-lb |
| 150 gr | 3,150 fps | 3,304 ft-lb |
What the numbers mean for a shot
SAAMI lists 3 reference bullet weights for the 270 Winchester Short Magnum, from 130 to 150 grains. The lightest, 130 grains, is listed at 3,275 fps, which computes to 3,096 ft-lb. The heaviest, 150 grains, is listed at 3,150 fps, or 3,304 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 270 WSM ammo range lists whatever its maker publishes for that item.
Twist rate, chamber and pressure
SAAMI’s standard test barrel for the 270 Winchester Short Magnum is 24.000 in long and rifled 1 turn in 10.00 in, with a .277 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 270 Winchester Short Magnum 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.
270 WSM vs 270: 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 | 270 Winchester Short Magnum | 270 Winchester |
|---|---|---|
| Maximum average pressure | 65,000 psi | 65,000 psi |
| Standard test barrel length | 24.000 in | 24.000 in |
| Test barrel twist rate | 1 turn in 10.00 in | 1 turn in 10.00 in |
| Test barrel groove diameter | .277 in | .277 in |
| Lightest reference load | 130 gr — 3,275 fps / 3,096 ft-lb | 100 gr — 3,300 fps / 2,418 ft-lb |
| A weight both list | 140 gr — 3,125 fps / 3,035 ft-lb | 140 gr — 2,950–3,090 fps / 2,705–2,968 ft-lb |
| Heaviest reference load | 150 gr — 3,150 fps / 3,304 ft-lb | 160 gr — 2,650 fps / 2,494 ft-lb |
The 270 Winchester Short Magnum and the 270 Winchester share the same maximum average pressure, 65,000 psi. At 140 grains, a weight both list, SAAMI’s 270 Winchester Short Magnum reference load is 3,125 fps and 3,035 ft-lb computed, against 3,090 fps and 2,968 ft-lb for the 270 Winchester. On that row the 270 Winchester Short Magnum 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: 270 ammo.
270 WSM ballistics questions
What is the maximum pressure of the 270 Winchester Short Magnum?
ANSI/SAAMI Z299.4 sets the maximum average pressure for the 270 Winchester Short Magnum at 65,000 psi.
What twist rate and barrel length does SAAMI use for the 270 Winchester Short Magnum?
SAAMI’s standard test barrel for the 270 Winchester Short Magnum is 24.000 in long and rifled 1 turn in 10.00 in. Your own rifle may differ, and a twist slower than a long, heavy bullet needs will not stabilise it.
What bullet weights does SAAMI list for the 270 Winchester Short Magnum?
SAAMI lists 3 reference weights, from 130 to 150 grains: 130, 140 and 150.
Is the 270 Winchester Short Magnum more powerful than the 270 Winchester?
Power is not a SAAMI measure, but reference muzzle energy is a fair proxy. At 140 grains, a weight both list, SAAMI’s 270 Winchester Short Magnum reference load is 3,125 fps and 3,035 ft-lb computed, against 3,090 fps and 2,968 ft-lb for the 270 Winchester.
How much does the 270 Winchester Short Magnum 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.
What is the effective range of the 270 Winchester Short Magnum?
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.
Where to buy these loads
Hilltop Armory carries 270 WSM ammunition from Federal, DoubleTap Ammunition, CorBon and Barnes. Browse the full 270 WSM ammo range.
