Load Specifications
Load data in caliber .338-378 Weath. Mag. with .338 | 250gr | Rhino Penetrator bullet and 60 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Vihtavuori N570, Hodgdon Retumbo and ReloadSwiss RS 76.
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.
A valid access license is required to use the Personalized Load Calculator.
You can find more information in our FAQ: How can I use the Personalized Load Calculator?
Max Load - Barrel Length: 26"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 3100 | <<locked>> | 88% | 55,013 psi | 86% | 2772 fps | 100% |
| Accurate High Country | <<locked>> | 86% | 56,869 psi | 89% | 2933 fps | 100% |
| Accurate MAGPRO | <<locked>> | 86% | 53,795 psi | 84% | 2877 fps | 99.4% |
| ADI AR 2209 | <<locked>> | 86% | 56,391 psi | 88% | 2858 fps | 100% |
| ADI AR 2213 | <<locked>> | 88% | 54,665 psi | 86% | 2874 fps | 99.9% |
| ADI AR 2217 | <<locked>> | 98% | 56,811 psi | 89% | 2904 fps | 100% |
| ADI AR 2218ᴾ | <<locked>> | 100% | 53,156 psi | 83% | 2959 fps | 98.4% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 55,434 psi | 87% | 2927 fps | 100% |
| Alliant Power Pro Varmint | <<locked>> | 86% | 56,536 psi | 89% | 2854 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 82% | 56,652 psi | 89% | 2838 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 86% | 55,927 psi | 88% | 2848 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 88% | 55,129 psi | 86% | 2871 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 90% | 56,898 psi | 89% | 2825 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 94% | 56,898 psi | 89% | 2900 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 86% | 57,653 psi | 90% | 2920 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 98% | 54,491 psi | 85% | 2943 fps | 98.5% |
| Alliant Reloder-50ᴾ | <<locked>> | 100% | 49,966 psi | 78% | 2864 fps | 97.2% |
| Baschieri & Pellagri 109 | <<locked>> | 90% | 55,347 psi | 87% | 2838 fps | 98.6% |
| Bofors RP15 | <<locked>> | 90% | 54,505 psi | 85% | 2861 fps | 100% |
| Bofors RP30 | <<locked>> | 96% | 56,637 psi | 89% | 2917 fps | 100% |
| Bofors RP5 | <<locked>> | 88% | 55,129 psi | 86% | 2871 fps | 100% |
| Hodgdon H1000 | <<locked>> | 94% | 54,520 psi | 85% | 2867 fps | 100% |
| Hodgdon H4831 | <<locked>> | 88% | 57,653 psi | 90% | 2861 fps | 99.8% |
| Hodgdon H4831 SC | <<locked>> | 88% | 56,623 psi | 89% | 2848 fps | 99.8% |
| Hodgdon Hybrid 100V | <<locked>> | 84% | 56,855 psi | 89% | 2762 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 94% | 55,985 psi | 88% | 2989 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,695 psi | 59% | 1785 fps | 100% |
| IMR 4350 | <<locked>> | 82% | 55,216 psi | 87% | 2779 fps | 100% |
| IMR 4831 | <<locked>> | 82% | 55,840 psi | 88% | 2779 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 86% | 54,563 psi | 86% | 2785 fps | 99.7% |
| IMR 7828 SSC | <<locked>> | 90% | 56,826 psi | 89% | 2913 fps | 100% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 50,691 psi | 79% | 2848 fps | 99.8% |
| Lovex S070 | <<locked>> | 82% | 57,421 psi | 90% | 2802 fps | 100% |
| Lovex S071 | <<locked>> | 94% | 56,695 psi | 89% | 2795 fps | 100% |
| Norma 204 | <<locked>> | 82% | 56,260 psi | 88% | 2835 fps | 100% |
| Norma 217ᴾ | <<locked>> | 100% | 51,764 psi | 81% | 2874 fps | 100% |
| Norma MRP | <<locked>> | 86% | 55,158 psi | 86% | 2884 fps | 100% |
| Norma URP | <<locked>> | 82% | 57,377 psi | 90% | 2818 fps | 100% |
| Ramshot Grand | <<locked>> | 88% | 53,925 psi | 85% | 2874 fps | 100% |
| Ramshot Hunter | <<locked>> | 82% | 56,231 psi | 88% | 2828 fps | 100% |
| Ramshot Magnum | <<locked>> | 92% | 56,347 psi | 88% | 2864 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,624 psi | 61% | 1827 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 94% | 56,623 psi | 89% | 2976 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 96% | 55,912 psi | 88% | 2946 fps | 99.7% |
| Rottweil R 904 | <<locked>> | 86% | 57,087 psi | 89% | 2828 fps | 99.9% |
| Rottweil R 905 | <<locked>> | 86% | 55,738 psi | 87% | 2841 fps | 100% |
| Shooters World SW4350 | <<locked>> | 82% | 57,421 psi | 90% | 2802 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 86% | 55,347 psi | 87% | 2835 fps | 100% |
| Somchem S361 | <<locked>> | 84% | 54,781 psi | 86% | 2766 fps | 99.6% |
| Somchem S365 | <<locked>> | 82% | 55,143 psi | 86% | 2772 fps | 100% |
| Somchem S385 | <<locked>> | 86% | 56,144 psi | 88% | 2808 fps | 100% |
| Vihtavuori N165 | <<locked>> | 90% | 55,985 psi | 88% | 2795 fps | 100% |
| Vihtavuori N170 | <<locked>> | 94% | 54,795 psi | 86% | 2818 fps | 97% |
| Vihtavuori N555 | <<locked>> | 86% | 55,158 psi | 86% | 2802 fps | 100% |
| Vihtavuori N560 | <<locked>> | 86% | 54,708 psi | 86% | 2887 fps | 99.7% |
| Vihtavuori N565 | <<locked>> | 92% | 55,303 psi | 87% | 2881 fps | 99.9% |
| Vihtavuori N568 | <<locked>> | 96% | 56,565 psi | 89% | 2946 fps | 99.6% |
| Vihtavuori N570 | <<locked>> | 96% | 53,708 psi | 84% | 2946 fps | 98.1% |
| Winchester StaBALL HD | <<locked>> | 90% | 56,623 psi | 89% | 2917 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 88% | 55,869 psi | 88% | 2808 fps | 100% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 26"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 3100 | <<locked>> | 80% | 42,221 psi | 66% | 2569 fps | 100% |
| Accurate High Country | <<locked>> | 80% | 46,122 psi | 72% | 2753 fps | 99.1% |
| Accurate MAGPRO | <<locked>> | 80% | 43,671 psi | 68% | 2694 fps | 97.7% |
| ADI AR 2209 | <<locked>> | 80% | 46,195 psi | 72% | 2694 fps | 99.6% |
| ADI AR 2213 | <<locked>> | 80% | 41,408 psi | 65% | 2638 fps | 98.2% |
| ADI AR 2217 | <<locked>> | 82% | 33,069 psi | 52% | 2444 fps | 95.8% |
| ADI AR 2218 | <<locked>> | 94% | 42,772 psi | 67% | 2749 fps | 95.4% |
| ADI AR 2225 | <<locked>> | 80% | 28,282 psi | 44% | 2359 fps | 96.8% |
| Alliant Power Pro Varmint | <<locked>> | 80% | 46,586 psi | 73% | 2694 fps | 99.6% |
| Alliant Reloder-16 | <<locked>> | 80% | 53,026 psi | 83% | 2789 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 46,151 psi | 72% | 2687 fps | 99.6% |
| Alliant Reloder-22 | <<locked>> | 80% | 42,134 psi | 66% | 2644 fps | 99.2% |
| Alliant Reloder-23 | <<locked>> | 80% | 40,901 psi | 64% | 2582 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 35,360 psi | 55% | 2530 fps | 99.9% |
| Alliant Reloder-26 | <<locked>> | 80% | 46,079 psi | 72% | 2746 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 43,540 psi | 68% | 2746 fps | 95.9% |
| Alliant Reloder-50 | <<locked>> | 96% | 43,018 psi | 67% | 2730 fps | 95.2% |
| Baschieri & Pellagri 109 | <<locked>> | 82% | 42,931 psi | 67% | 2612 fps | 95.8% |
| Bofors RP15 | <<locked>> | 80% | 39,262 psi | 62% | 2582 fps | 98.5% |
| Bofors RP30 | <<locked>> | 80% | 32,938 psi | 52% | 2464 fps | 96% |
| Bofors RP5 | <<locked>> | 80% | 42,134 psi | 66% | 2644 fps | 99.2% |
| Hodgdon H1000 | <<locked>> | 80% | 33,533 psi | 53% | 2461 fps | 96.7% |
| Hodgdon H4831 | <<locked>> | 80% | 44,019 psi | 69% | 2638 fps | 98.2% |
| Hodgdon H4831 SC | <<locked>> | 80% | 43,250 psi | 68% | 2621 fps | 98% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 50,009 psi | 78% | 2667 fps | 100% |
| Hodgdon Retumbo | 89.2 gr | 80% | 34,476 psi | 54% | 2569 fps | 98.3% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,282 psi | 44% | 1594 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 51,880 psi | 81% | 2726 fps | 100% |
| IMR 4831 | <<locked>> | 80% | 52,388 psi | 82% | 2730 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 45,179 psi | 71% | 2628 fps | 98.5% |
| IMR 7828 SSC | <<locked>> | 80% | 40,132 psi | 63% | 2621 fps | 97.9% |
| IMR 8133 Enduron | <<locked>> | 86% | 31,560 psi | 49% | 2451 fps | 95.2% |
| Lovex S070 | <<locked>> | 80% | 53,925 psi | 85% | 2753 fps | 100% |
| Lovex S071 | <<locked>> | 80% | 36,347 psi | 57% | 2451 fps | 99.5% |
| Norma 204 | <<locked>> | 80% | 52,736 psi | 83% | 2782 fps | 100% |
| Norma 217 | <<locked>> | 82% | 27,746 psi | 43% | 2359 fps | 95.7% |
| Norma MRP | <<locked>> | 80% | 44,628 psi | 70% | 2713 fps | 100% |
| Norma URP | <<locked>> | 80% | 53,824 psi | 84% | 2769 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 40,089 psi | 63% | 2631 fps | 98.3% |
| Ramshot Hunter | <<locked>> | 80% | 52,808 psi | 83% | 2779 fps | 100% |
| Ramshot Magnum | <<locked>> | 80% | 36,085 psi | 57% | 2513 fps | 98.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,051 psi | 46% | 1634 fps | 100% |
| ReloadSwiss RS 76 | 95.5 gr | 80% | 33,663 psi | 53% | 2546 fps | 98.9% |
| ReloadSwiss RS 80 | <<locked>> | 84% | 35,578 psi | 56% | 2562 fps | 95.4% |
| Rottweil R 904 | <<locked>> | 80% | 47,050 psi | 74% | 2667 fps | 99.1% |
| Rottweil R 905 | <<locked>> | 80% | 45,730 psi | 72% | 2677 fps | 99.6% |
| Shooters World SW4350 | <<locked>> | 80% | 53,925 psi | 85% | 2753 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 45,397 psi | 71% | 2674 fps | 99.6% |
| Somchem S361 | <<locked>> | 80% | 47,877 psi | 75% | 2654 fps | 98.8% |
| Somchem S365 | <<locked>> | 80% | 51,590 psi | 81% | 2723 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 46,122 psi | 72% | 2651 fps | 99.9% |
| Vihtavuori N165 | <<locked>> | 80% | 40,335 psi | 63% | 2536 fps | 99.2% |
| Vihtavuori N170 | <<locked>> | 90% | 47,964 psi | 75% | 2703 fps | 95.4% |
| Vihtavuori N555 | <<locked>> | 80% | 45,440 psi | 71% | 2654 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 44,367 psi | 70% | 2707 fps | 98.4% |
| Vihtavuori N565 | <<locked>> | 80% | 36,927 psi | 58% | 2536 fps | 96.7% |
| Vihtavuori N568 | <<locked>> | 84% | 36,985 psi | 58% | 2582 fps | 95.3% |
| Vihtavuori N570 | 104.2 gr | 90% | 43,381 psi | 68% | 2756 fps | 95.4% |
| Winchester StaBALL HD | <<locked>> | 80% | 38,841 psi | 61% | 2644 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 42,482 psi | 67% | 2589 fps | 99.2% |
Recommended = one of the top powders for this cartridge and bullet combination.
ᴾ possible press load - work up slowly to this load while watching for signs of excessive pressure.
This overview compares 60 powders for .338-378 Weath. Mag. loaded with the .338 | 250gr | Rhino Penetrator. Hodgdon Retumbo delivers the highest muzzle velocity at 2,989 fps; across all powders the maximum-charge window runs from 1,785 fps to 2,989 fps. ADI AR 2218 gives the best case fill at 100 %, and 60 of the 60 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (440 MPa), the top charges use 59–90 %, leaving at least 10 % headroom. The 250.0 gr projectile in 0.338" calls for a 1:13.0 twist; slower twists will usually not stabilise this weight. ADI AR 2218, ADI AR 2225, Alliant Reloder-50 reach 100 % fill or more at maximum charge, so these are compressed loads: they need a long drop tube to seat cleanly and react sensitively to the case capacity of your own brass lot. Vihtavuori N570, Hodgdon Retumbo, ReloadSwiss RS 76 rank at the top here: for .338-378 Weath. Mag. with the .338 | 250gr | Rhino Penetrator they combine a high case fill with complete burn and sit in the upper velocity band. Always begin at the start load and work up in small increments while checking case and primer for pressure signs.