Load Specifications
Load data in caliber .300 Rem. Ultra Mag. with .308 | 166gr | Hammer Stone Hammer bullet and 1 powder. The key underlying parameters are shown in the table above.
Important Notice: DO NOT go below Minimum Charge or above Maximum Charge. Since we have no control over the equipment and components used, any responsibility and liability for the results achieved is rejected.
Only powders/loads that match the current filter criteria are displayed: max pressure of a load ≤ 90% of max. standardized pressure, fill rate ≥ 80% and propellant combustion ≥ 95%. Use the sliders above the tables to adjust these thresholds.
Charge: Powder weight in grains. Start with the minimum load and work up carefully.
FR (Fill Rate): Case fill as a percentage. Values above 100% mean compressed loads.
MaxP / %: Maximum chamber pressure in bar and as a percentage of the standardized maximum for this caliber.
V(0): Muzzle velocity in feet per second (fps) at the standardized barrel length.
z (Powder Burn): Estimated propellant combustion percentage at bullet exit.
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Max Load - Barrel Length: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Alliant Power Pro Varmint | <<locked>> | 90% | 57,870 psi | 89% | 2999 fps | 99.7% |
Start Load - Barrel Length: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Alliant Power Pro Varmint | <<locked>> | 80% | 41,031 psi | 63% | 2703 fps | 96.8% |
This overview compares 1 powders for .300 Rem. Ultra Mag. loaded with the .308 | 166gr | Hammer Stone Hammer. Alliant Power Pro Varmint delivers the highest muzzle velocity at 2,999 fps; across all powders the maximum-charge window runs from 2,999 fps to 2,999 fps. Alliant Power Pro Varmint gives the best case fill at 90 %, and 1 of the 1 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (448 MPa), the top charges use 89–89 %, leaving at least 11 % headroom. The 166.0 gr projectile in 0.308" calls for a 1:12.5 twist; slower twists will usually not stabilise this weight. Always begin at the start load and work up in small increments while checking case and primer for pressure signs.