The 257 Roberts is a centerfire rifle cartridge standardised by SAAMI in ANSI/SAAMI Z299.4. SAAMI sets its maximum average pressure at 54,000 psi. This guide sets out SAAMI’s published reference velocity for each bullet weight, computes the muzzle energy each one carries, and compares the 257 Roberts with the 25-06 Remington on the same basis.
257 Roberts 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 |
|---|---|---|
| 87 gr | 3,150 fps | 1,916 ft-lb |
| 100 gr | 2,880 fps | 1,841 ft-lb |
| 117 gr | 2,630 fps | 1,797 ft-lb |
What the numbers mean for a shot
SAAMI lists 3 reference bullet weights for the 257 Roberts, from 87 to 117 grains. The lightest, 87 grains, is listed at 3,150 fps, which computes to 1,916 ft-lb. The heaviest, 117 grains, is listed at 2,630 fps, which computes to 1,797 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 257 Roberts ammo range lists whatever its maker publishes for that item.
Twist rate, chamber and pressure
The maximum average pressure is 54,000 psi. Fire 257 Roberts 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.
257 Roberts vs 25-06: 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 | 257 Roberts | 25-06 Remington |
|---|---|---|
| Maximum average pressure | 54,000 psi | 63,000 psi |
| Standard test barrel length | Not read from the drawing | 24.000 in |
| Test barrel twist rate | Not read from the drawing | 1 turn in 10.00 in |
| Test barrel groove diameter | Not read from the drawing | .257 in |
| Lightest reference load | 87 gr — 3,150 fps / 1,916 ft-lb | 85 gr — 3,510 fps / 2,325 ft-lb |
| A weight both list | 100 gr — 2,880 fps / 1,841 ft-lb | 100 gr — 3,210 fps / 2,288 ft-lb |
| Heaviest reference load | 117 gr — 2,630 fps / 1,797 ft-lb | 120 gr — 2,975 fps / 2,358 ft-lb |
SAAMI standardises the 257 Roberts at 54,000 psi and the 25-06 Remington at 63,000 psi, so the 257 Roberts runs 9,000 psi lower. At 100 grains, a weight both list, SAAMI’s 257 Roberts reference velocity is 2,880 fps (1,841 ft-lb computed), against 3,210 fps (2,288 ft-lb) for the 25-06 Remington. On that row the 25-06 Remington 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: 25-06 ammo.
257 Roberts ballistics questions
What is the maximum pressure of the 257 Roberts?
ANSI/SAAMI Z299.4 sets the maximum average pressure for the 257 Roberts at 54,000 psi.
What bullet weights does SAAMI list for the 257 Roberts?
SAAMI lists 3 reference weights, from 87 to 117 grains: 87, 100 and 117.
Is the 257 Roberts more powerful than the 25-06 Remington?
Power is not a SAAMI measure, but reference muzzle energy is a fair proxy. At 100 grains, a weight both list, SAAMI’s 257 Roberts reference velocity is 2,880 fps (1,841 ft-lb computed), against 3,210 fps (2,288 ft-lb) for the 25-06 Remington.
What is the effective range of the 257 Roberts?
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 257 Roberts 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 257 Roberts ammunition from DoubleTap Ammunition, Hornady, Federal, HSM Ammunition, Norma and Nosler. Browse the full 257 Roberts ammo range.
