The 30 Thompson Center is a centerfire rifle cartridge standardised by SAAMI in ANSI/SAAMI Z299.4. SAAMI sets its maximum average pressure at 62,000 psi, and measures its reference velocities in a 24.000 in standard test barrel rifled 1 turn in 12.00 in. This guide sets out SAAMI’s published reference velocity for each bullet weight, computes the muzzle energy each one carries, and compares the 30 Thompson Center with the 308 Winchester on the same basis.
30 TC 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 |
|---|---|---|
| 150 gr | 2,985 fps | 2,967 ft-lb |
| 165 gr | 2,835 fps | 2,944 ft-lb |
What the numbers mean for a shot
SAAMI lists two reference bullet weights for the 30 Thompson Center, 150 and 165 grains. The lighter, 150 grains, is listed at 2,985 fps, which computes to 2,967 ft-lb. The heavier, 165 grains, is listed at 2,835 fps, which computes to 2,944 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 30 TC ammo range lists whatever its maker publishes for that item.
Twist rate, chamber and pressure
SAAMI’s standard test barrel for the 30 Thompson Center is 24.000 in long and rifled 1 turn in 12.00 in, with a .308 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 62,000 psi. Fire 30 Thompson Center 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.
30 TC vs 308: 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 | 30 Thompson Center | 308 Winchester |
|---|---|---|
| Maximum average pressure | 62,000 psi | 62,000 psi |
| Standard test barrel length | 24.000 in | 24.000 in |
| Test barrel twist rate | 1 turn in 12.00 in | 1 turn in 12.00 in |
| Test barrel groove diameter | .308 in | .308 in |
| Lightest reference load | 150 gr — 2,985 fps / 2,967 ft-lb | 55 gr — 3,750 fps / 1,717 ft-lb |
| A weight both list | 165 gr — 2,835 fps / 2,944 ft-lb | 165 gr — 2,870–2,880 fps / 3,017–3,038 ft-lb |
| Heaviest reference load | 165 gr — 2,835 fps / 2,944 ft-lb | 200 gr — 2,440 fps / 2,643 ft-lb |
The 30 Thompson Center and the 308 Winchester share the same maximum average pressure, 62,000 psi. At 165 grains, a weight both list, SAAMI’s 30 Thompson Center reference velocity is 2,835 fps (2,944 ft-lb computed), against up to 2,880 fps (3,038 ft-lb) for the 308 Winchester. On that row the 308 Winchester 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: 308 ammo.
30 TC ballistics questions
What is the maximum pressure of the 30 Thompson Center?
ANSI/SAAMI Z299.4 sets the maximum average pressure for the 30 Thompson Center at 62,000 psi.
What twist rate and barrel length does SAAMI use for the 30 Thompson Center?
SAAMI’s standard test barrel for the 30 Thompson Center is 24.000 in long and rifled 1 turn in 12.00 in. Your own rifle may differ.
What bullet weights does SAAMI list for the 30 Thompson Center?
SAAMI lists 2 reference weights, from 150 to 165 grains: 150 and 165.
Is the 30 Thompson Center more powerful than the 308 Winchester?
Power is not a SAAMI measure, but reference muzzle energy is a fair proxy. At 165 grains, a weight both list, SAAMI’s 30 Thompson Center reference velocity is 2,835 fps (2,944 ft-lb computed), against up to 2,880 fps (3,038 ft-lb) for the 308 Winchester.
What is the effective range of the 30 Thompson Center?
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 30 Thompson Center 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 30 TC ammunition from Hornady. Browse the full 30 TC ammo range.
