Load Specifications
Load data in caliber .338-378 Weath. Mag. with .338 | 250gr | Sierra MatchKing bullet and 58 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.
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Max Load - Barrel Length: 26"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 3100 | <<locked>> | 88% | 55,027 psi | 86% | 2772 fps | 100% |
| Accurate MAGPRO | <<locked>> | 86% | 53,824 psi | 84% | 2877 fps | 99.4% |
| ADI AR 2209 | <<locked>> | 86% | 56,405 psi | 88% | 2858 fps | 100% |
| ADI AR 2213 | <<locked>> | 88% | 54,679 psi | 86% | 2874 fps | 99.9% |
| ADI AR 2217 | <<locked>> | 98% | 56,826 psi | 89% | 2907 fps | 100% |
| ADI AR 2218ᴾ | <<locked>> | 100% | 53,171 psi | 83% | 2963 fps | 98.4% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 55,288 psi | 87% | 2927 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 82% | 56,666 psi | 89% | 2841 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 86% | 55,941 psi | 88% | 2848 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 88% | 55,143 psi | 86% | 2871 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 90% | 56,913 psi | 89% | 2828 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 94% | 56,913 psi | 89% | 2900 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 86% | 57,667 psi | 90% | 2920 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 98% | 54,447 psi | 85% | 2943 fps | 98.5% |
| Alliant Reloder-50ᴾ | <<locked>> | 100% | 49,995 psi | 78% | 2864 fps | 97.2% |
| Baschieri & Pellagri 109 | <<locked>> | 90% | 55,332 psi | 87% | 2838 fps | 98.6% |
| Bofors RP15 | <<locked>> | 90% | 54,520 psi | 85% | 2861 fps | 100% |
| Bofors RP30 | <<locked>> | 96% | 56,652 psi | 89% | 2920 fps | 100% |
| Bofors RP5 | <<locked>> | 88% | 55,143 psi | 86% | 2871 fps | 100% |
| Hodgdon H1000 | <<locked>> | 94% | 54,534 psi | 85% | 2871 fps | 100% |
| Hodgdon H4831 | <<locked>> | 88% | 57,624 psi | 90% | 2864 fps | 99.8% |
| Hodgdon H4831 SC | <<locked>> | 88% | 56,637 psi | 89% | 2851 fps | 99.8% |
| Hodgdon Hybrid 100V | <<locked>> | 84% | 56,695 psi | 89% | 2759 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 94% | 55,840 psi | 88% | 2989 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,710 psi | 59% | 1785 fps | 100% |
| IMR 4350 | <<locked>> | 82% | 55,230 psi | 87% | 2779 fps | 100% |
| IMR 4831 | <<locked>> | 82% | 55,854 psi | 88% | 2779 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 86% | 54,578 psi | 86% | 2789 fps | 99.7% |
| IMR 7828 SSC | <<locked>> | 90% | 56,840 psi | 89% | 2917 fps | 100% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 50,705 psi | 79% | 2851 fps | 99.8% |
| Lovex S070 | <<locked>> | 82% | 57,435 psi | 90% | 2805 fps | 100% |
| Lovex S071 | <<locked>> | 94% | 56,666 psi | 89% | 2795 fps | 100% |
| Norma 204 | <<locked>> | 82% | 56,275 psi | 88% | 2835 fps | 100% |
| Norma 217ᴾ | <<locked>> | 100% | 51,779 psi | 81% | 2874 fps | 100% |
| Norma MRP | <<locked>> | 86% | 55,172 psi | 86% | 2887 fps | 100% |
| Norma URP | <<locked>> | 82% | 57,392 psi | 90% | 2822 fps | 100% |
| Ramshot Grand | <<locked>> | 88% | 53,940 psi | 85% | 2877 fps | 100% |
| Ramshot Hunter | <<locked>> | 82% | 56,246 psi | 88% | 2831 fps | 100% |
| Ramshot Magnum | <<locked>> | 92% | 56,333 psi | 88% | 2864 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,638 psi | 61% | 1827 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 94% | 56,637 psi | 89% | 2979 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 96% | 55,941 psi | 88% | 2946 fps | 99.8% |
| Rottweil R 904 | <<locked>> | 86% | 57,058 psi | 89% | 2828 fps | 99.9% |
| Rottweil R 905 | <<locked>> | 86% | 55,753 psi | 87% | 2841 fps | 100% |
| Shooters World SW4350 | <<locked>> | 82% | 57,435 psi | 90% | 2805 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 86% | 55,361 psi | 87% | 2838 fps | 100% |
| Somchem S361 | <<locked>> | 84% | 54,795 psi | 86% | 2766 fps | 99.6% |
| Somchem S365 | <<locked>> | 82% | 55,100 psi | 86% | 2772 fps | 100% |
| Somchem S385 | <<locked>> | 86% | 55,999 psi | 88% | 2808 fps | 100% |
| Vihtavuori N165 | <<locked>> | 90% | 55,840 psi | 88% | 2795 fps | 100% |
| Vihtavuori N170 | <<locked>> | 94% | 54,781 psi | 86% | 2818 fps | 97% |
| Vihtavuori N555 | <<locked>> | 86% | 55,158 psi | 86% | 2805 fps | 100% |
| Vihtavuori N560 | <<locked>> | 86% | 54,694 psi | 86% | 2890 fps | 99.8% |
| Vihtavuori N565 | <<locked>> | 92% | 55,288 psi | 87% | 2881 fps | 99.9% |
| Vihtavuori N568 | <<locked>> | 96% | 56,579 psi | 89% | 2949 fps | 99.6% |
| Vihtavuori N570 | <<locked>> | 98% | 57,725 psi | 90% | 3012 fps | 98.7% |
| Winchester StaBALL HD | <<locked>> | 90% | 56,652 psi | 89% | 2917 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 88% | 55,883 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% | 42,235 psi | 66% | 2569 fps | 100% |
| Accurate MAGPRO | <<locked>> | 80% | 43,540 psi | 68% | 2694 fps | 97.7% |
| ADI AR 2209 | <<locked>> | 80% | 46,209 psi | 72% | 2694 fps | 99.6% |
| ADI AR 2213 | <<locked>> | 80% | 41,423 psi | 65% | 2638 fps | 98.2% |
| ADI AR 2217 | <<locked>> | 82% | 33,069 psi | 52% | 2448 fps | 95.8% |
| ADI AR 2218 | <<locked>> | 94% | 42,786 psi | 67% | 2749 fps | 95.4% |
| ADI AR 2225 | <<locked>> | 80% | 28,268 psi | 44% | 2359 fps | 96.8% |
| Alliant Reloder-16 | <<locked>> | 80% | 53,040 psi | 83% | 2789 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 46,166 psi | 72% | 2687 fps | 99.6% |
| Alliant Reloder-22 | <<locked>> | 80% | 42,119 psi | 66% | 2644 fps | 99.2% |
| Alliant Reloder-23 | <<locked>> | 80% | 40,915 psi | 64% | 2585 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 35,375 psi | 55% | 2533 fps | 99.9% |
| Alliant Reloder-26 | <<locked>> | 80% | 46,093 psi | 72% | 2749 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 92% | 43,569 psi | 68% | 2746 fps | 96% |
| Alliant Reloder-50 | <<locked>> | 96% | 43,047 psi | 67% | 2733 fps | 95.2% |
| Baschieri & Pellagri 109 | <<locked>> | 82% | 42,946 psi | 67% | 2612 fps | 95.8% |
| Bofors RP15 | <<locked>> | 80% | 39,247 psi | 62% | 2585 fps | 98.6% |
| Bofors RP30 | <<locked>> | 80% | 32,938 psi | 52% | 2467 fps | 96% |
| Bofors RP5 | <<locked>> | 80% | 42,119 psi | 66% | 2644 fps | 99.2% |
| Hodgdon H1000 | <<locked>> | 80% | 33,547 psi | 53% | 2461 fps | 96.7% |
| Hodgdon H4831 | <<locked>> | 80% | 44,034 psi | 69% | 2638 fps | 98.2% |
| Hodgdon H4831 SC | <<locked>> | 80% | 43,265 psi | 68% | 2621 fps | 98% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 50,009 psi | 78% | 2667 fps | 100% |
| Hodgdon Retumbo | 89.2 gr | 80% | 34,490 psi | 54% | 2569 fps | 98.3% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,282 psi | 44% | 1594 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 51,895 psi | 81% | 2726 fps | 100% |
| IMR 4831 | <<locked>> | 80% | 52,402 psi | 82% | 2730 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 45,194 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% | 53,940 psi | 85% | 2753 fps | 100% |
| Lovex S071 | <<locked>> | 80% | 36,361 psi | 57% | 2454 fps | 99.5% |
| Norma 204 | <<locked>> | 80% | 52,605 psi | 82% | 2782 fps | 100% |
| Norma 217 | <<locked>> | 82% | 27,760 psi | 44% | 2362 fps | 95.7% |
| Norma MRP | <<locked>> | 80% | 44,643 psi | 70% | 2713 fps | 100% |
| Norma URP | <<locked>> | 80% | 53,838 psi | 84% | 2769 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 40,074 psi | 63% | 2631 fps | 98.3% |
| Ramshot Hunter | <<locked>> | 80% | 52,634 psi | 82% | 2779 fps | 100% |
| Ramshot Magnum | <<locked>> | 80% | 36,056 psi | 56% | 2516 fps | 98.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,051 psi | 46% | 1634 fps | 100% |
| ReloadSwiss RS 76 | 95.5 gr | 80% | 33,649 psi | 53% | 2546 fps | 98.9% |
| ReloadSwiss RS 80 | <<locked>> | 84% | 35,592 psi | 56% | 2566 fps | 95.4% |
| Rottweil R 904 | <<locked>> | 80% | 47,065 psi | 74% | 2667 fps | 99.2% |
| Rottweil R 905 | <<locked>> | 80% | 45,745 psi | 72% | 2677 fps | 99.6% |
| Shooters World SW4350 | <<locked>> | 80% | 53,940 psi | 85% | 2753 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 45,397 psi | 71% | 2674 fps | 99.6% |
| Somchem S361 | <<locked>> | 80% | 47,892 psi | 75% | 2657 fps | 98.8% |
| Somchem S365 | <<locked>> | 80% | 51,605 psi | 81% | 2723 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 46,093 psi | 72% | 2651 fps | 99.9% |
| Vihtavuori N165 | <<locked>> | 80% | 40,350 psi | 63% | 2536 fps | 99.2% |
| Vihtavuori N170 | <<locked>> | 90% | 47,964 psi | 75% | 2703 fps | 95.4% |
| Vihtavuori N555 | <<locked>> | 80% | 45,455 psi | 71% | 2657 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 44,382 psi | 70% | 2710 fps | 98.4% |
| Vihtavuori N565 | <<locked>> | 80% | 36,898 psi | 58% | 2536 fps | 96.7% |
| Vihtavuori N568 | <<locked>> | 84% | 36,869 psi | 58% | 2582 fps | 95.3% |
| Vihtavuori N570 | 104.2 gr | 90% | 43,395 psi | 68% | 2756 fps | 95.5% |
| Winchester StaBALL HD | <<locked>> | 80% | 38,711 psi | 61% | 2641 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 42,453 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 58 powders for .338-378 Weath. Mag. loaded with the .338 | 250gr | Sierra MatchKing. Vihtavuori N570 delivers the highest muzzle velocity at 3,012 fps; across all powders the maximum-charge window runs from 1,785 fps to 3,012 fps. ADI AR 2218 gives the best case fill at 100 %, and 58 of the 58 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 1:12.5 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 | Sierra MatchKing 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.