The 17 Winchester Super Magnum is a rimfire cartridge standardised by SAAMI in ANSI/SAAMI Z299.1. SAAMI sets its maximum average pressure at 33,000 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 17 Winchester Super Magnum with the 17 Hornady Magnum Rimfire on the same basis.
17 WSM ballistics chart: SAAMI reference data
SAAMI lists rimfire reference loads by bullet weight and by bullet type, and publishes a nominal mean instrumental velocity for each, measured at 15 feet from the standard test barrel. Bullet types are shown as the code SAAMI prints. It does not publish energy, so the ft-lb column is computed.
Scroll the table sideways for the remaining columns.
| Bullet weight | Bullet type (SAAMI code) | Reference velocity | Computed muzzle energy |
|---|---|---|---|
| 20 gr | PT | 3,000 fps | 400 ft-lb |
| 25 gr | PT | 2,600 fps | 375 ft-lb |
What the numbers mean for a shot
SAAMI lists two reference bullet weights for the 17 Winchester Super Magnum, 20 and 25 grains. The lighter, 20 grains, is listed at 3,000 fps, which computes to 400 ft-lb. The heavier, 25 grains, is listed at 2,600 fps, which computes to 375 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 17 WSM ammo range lists whatever its maker publishes for that item.
Barrel, chamber and pressure
SAAMI’s standard test barrel for the 17 Winchester Super Magnum is 24.000 in long and rifled 1 turn in 9.00 in, with a .172 in groove diameter. That is the barrel every reference velocity above was measured in, not a statement about your firearm: rimfire barrels vary widely in length, and a shorter barrel gives lower velocity. The maximum average pressure is 33,000 psi. Fire 17 Winchester Super 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.
17 WSM vs 17 HMR: 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 | 17 Winchester Super Magnum | 17 Hornady Magnum Rimfire |
|---|---|---|
| Maximum average pressure | 33,000 psi | 26,000 psi |
| Standard test barrel length | 24.000 in | 24.000 in |
| Test barrel twist rate | 1 turn in 9.00 in | 1 turn in 9.00 in |
| Test barrel groove diameter | .172 in | .1720 in |
| Lightest reference load | 20 gr — 3,000 fps / 400 ft-lb | 15.5 gr — 2,475 fps / 211 ft-lb |
| A weight both list | 20 gr — 3,000 fps / 400 ft-lb | 20 gr — 2,350 fps / 245 ft-lb |
| Heaviest reference load | 25 gr — 2,600 fps / 375 ft-lb | 20 gr — 2,350 fps / 245 ft-lb |
SAAMI standardises the 17 Winchester Super Magnum at 33,000 psi and the 17 Hornady Magnum Rimfire at 26,000 psi, so the 17 Winchester Super Magnum runs 7,000 psi higher. At 20 grains, a weight both list, SAAMI’s 17 Winchester Super Magnum reference velocity is 3,000 fps (400 ft-lb computed), against 2,350 fps (245 ft-lb) for the 17 Hornady Magnum Rimfire. On that row the 17 Winchester Super 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: 17 HMR ammo.
17 WSM ballistics questions
What is the maximum pressure of the 17 Winchester Super Magnum?
ANSI/SAAMI Z299.1 sets the maximum average pressure for the 17 Winchester Super Magnum at 33,000 psi.
What twist rate and barrel length does SAAMI use for the 17 Winchester Super Magnum?
SAAMI’s standard test barrel for the 17 Winchester Super Magnum is 24.000 in long and rifled 1 turn in 9.00 in. Your own firearm may differ.
What bullet weights does SAAMI list for the 17 Winchester Super Magnum?
SAAMI lists 2 reference weights, from 20 to 25 grains: 20 and 25.
Is the 17 Winchester Super Magnum more powerful than the 17 Hornady Magnum Rimfire?
Power is not a SAAMI measure, but reference muzzle energy is a fair proxy. At 20 grains, a weight both list, SAAMI’s 17 Winchester Super Magnum reference velocity is 3,000 fps (400 ft-lb computed), against 2,350 fps (245 ft-lb) for the 17 Hornady Magnum Rimfire.
What is the effective range of the 17 Winchester Super 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.
How much does the 17 Winchester Super Magnum 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 17 WSM ammunition from Winchester. Browse the full 17 WSM ammo range.
