Load Specifications
Load data in caliber .338-378 Weath. Mag. with .338 | 300gr | Sierra HPBT LR MatchKing bullet and 57 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ADI AR 2218, Vihtavuori N570 and Alliant Reloder-33.
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>> | 84% | 54,404 psi | 85% | 2530 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 48,718 psi | 76% | 2582 fps | 98.5% |
| Accurate High Country | <<locked>> | 82% | 56,289 psi | 88% | 2684 fps | 100% |
| Accurate MAGPRO | <<locked>> | 84% | 57,058 psi | 89% | 2694 fps | 100% |
| ADI AR 2209 | <<locked>> | 82% | 55,245 psi | 87% | 2605 fps | 100% |
| ADI AR 2213 | <<locked>> | 84% | 53,998 psi | 85% | 2631 fps | 100% |
| ADI AR 2217 | <<locked>> | 94% | 56,782 psi | 89% | 2671 fps | 100% |
| ADI AR 2218 | <<locked>> | 98% | 56,942 psi | 89% | 2805 fps | 99.9% |
| ADI AR 2225 | <<locked>> | 96% | 56,173 psi | 88% | 2694 fps | 100% |
| Alliant Power Pro Varmint | <<locked>> | 82% | 55,492 psi | 87% | 2605 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 82% | 54,940 psi | 86% | 2598 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 84% | 54,607 psi | 86% | 2625 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 86% | 56,521 psi | 89% | 2579 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 90% | 57,159 psi | 90% | 2654 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 82% | 57,261 psi | 90% | 2664 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 94% | 54,955 psi | 86% | 2723 fps | 99.7% |
| Alliant Reloder-50 | <<locked>> | 98% | 54,665 psi | 86% | 2720 fps | 99.4% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 57,653 psi | 90% | 2651 fps | 99.8% |
| Bofors RP15 | <<locked>> | 88% | 57,667 psi | 90% | 2667 fps | 100% |
| Bofors RP30 | <<locked>> | 92% | 56,927 psi | 89% | 2687 fps | 100% |
| Bofors RP5 | <<locked>> | 84% | 54,607 psi | 86% | 2625 fps | 100% |
| Hodgdon H1000 | <<locked>> | 90% | 54,288 psi | 85% | 2631 fps | 100% |
| Hodgdon H4831 | <<locked>> | 84% | 56,492 psi | 89% | 2618 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 84% | 55,492 psi | 87% | 2605 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 90% | 56,652 psi | 89% | 2746 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,000 psi | 60% | 1634 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 56,652 psi | 89% | 2592 fps | 100% |
| IMR 7828 SSC | <<locked>> | 86% | 56,420 psi | 88% | 2671 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 90% | 55,129 psi | 86% | 2559 fps | 97.4% |
| IMR 8133 Enduron | <<locked>> | 98% | 54,998 psi | 86% | 2680 fps | 100% |
| Lovex D100 | <<locked>> | 94% | 55,622 psi | 87% | 2612 fps | 96.6% |
| Lovex S071 | <<locked>> | 90% | 56,391 psi | 88% | 2556 fps | 100% |
| Norma 217 | <<locked>> | 98% | 56,405 psi | 88% | 2697 fps | 100% |
| Norma MRP | <<locked>> | 82% | 54,665 psi | 86% | 2638 fps | 100% |
| Ramshot Grand | <<locked>> | 84% | 53,679 psi | 84% | 2638 fps | 100% |
| Ramshot LRT | <<locked>> | 98% | 56,579 psi | 89% | 2740 fps | 96.7% |
| Ramshot Magnum | <<locked>> | 88% | 55,970 psi | 88% | 2625 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,030 psi | 61% | 1670 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 90% | 57,188 psi | 90% | 2736 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 92% | 56,188 psi | 88% | 2720 fps | 100% |
| Rottweil R 904 | <<locked>> | 82% | 55,724 psi | 87% | 2579 fps | 100% |
| Rottweil R 905 | <<locked>> | 82% | 54,781 psi | 86% | 2592 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 94% | 55,622 psi | 87% | 2612 fps | 96.6% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 50,879 psi | 80% | 2592 fps | 98.5% |
| SNPE Vectan Tubal 8000 | <<locked>> | 82% | 54,418 psi | 85% | 2589 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 56,782 psi | 89% | 2575 fps | 100% |
| Somchem S385 | <<locked>> | 82% | 55,085 psi | 86% | 2562 fps | 100% |
| Vihtavuori 24N41 | <<locked>> | 98% | 54,621 psi | 86% | 2651 fps | 95.9% |
| Vihtavuori N165 | <<locked>> | 86% | 54,969 psi | 86% | 2552 fps | 100% |
| Vihtavuori N170 | <<locked>> | 90% | 54,027 psi | 85% | 2595 fps | 98.5% |
| Vihtavuori N555 | <<locked>> | 82% | 54,853 psi | 86% | 2559 fps | 100% |
| Vihtavuori N560 | <<locked>> | 84% | 57,711 psi | 90% | 2697 fps | 100% |
| Vihtavuori N565 | <<locked>> | 88% | 55,158 psi | 86% | 2644 fps | 100% |
| Vihtavuori N568 | <<locked>> | 92% | 56,695 psi | 89% | 2717 fps | 100% |
| Vihtavuori N570 | <<locked>> | 92% | 54,273 psi | 85% | 2726 fps | 99.4% |
| Winchester StaBALL HD | <<locked>> | 86% | 57,421 psi | 90% | 2671 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 84% | 54,752 psi | 86% | 2562 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% | 47,601 psi | 75% | 2438 fps | 100% |
| Accurate 8700 | <<locked>> | 92% | 36,709 psi | 58% | 2359 fps | 95.2% |
| Accurate High Country | <<locked>> | 80% | 52,518 psi | 82% | 2631 fps | 100% |
| Accurate MAGPRO | <<locked>> | 80% | 49,734 psi | 78% | 2585 fps | 99.8% |
| ADI AR 2209 | <<locked>> | 80% | 51,822 psi | 81% | 2559 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 47,050 psi | 74% | 2526 fps | 99.9% |
| ADI AR 2217 | <<locked>> | 80% | 35,201 psi | 55% | 2310 fps | 98.7% |
| ADI AR 2218 | 99.3 gr | 86% | 36,956 psi | 58% | 2431 fps | 95.8% |
| ADI AR 2225 | <<locked>> | 80% | 32,503 psi | 51% | 2293 fps | 99.8% |
| Alliant Power Pro Varmint | <<locked>> | 80% | 51,982 psi | 81% | 2556 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 51,488 psi | 81% | 2549 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 47,848 psi | 75% | 2526 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 46,688 psi | 73% | 2448 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 40,814 psi | 64% | 2421 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 80% | 53,156 psi | 83% | 2612 fps | 100% |
| Alliant Reloder-33 | 96.4 gr | 82% | 35,273 psi | 55% | 2365 fps | 95.3% |
| Alliant Reloder-50 | <<locked>> | 88% | 38,029 psi | 60% | 2425 fps | 95.8% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 44,715 psi | 70% | 2448 fps | 98.2% |
| Bofors RP15 | <<locked>> | 80% | 44,585 psi | 70% | 2470 fps | 100% |
| Bofors RP30 | <<locked>> | 80% | 38,043 psi | 60% | 2379 fps | 99.2% |
| Bofors RP5 | <<locked>> | 80% | 47,848 psi | 75% | 2526 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 38,305 psi | 60% | 2372 fps | 99.6% |
| Hodgdon H4831 | <<locked>> | 80% | 49,327 psi | 77% | 2513 fps | 99.9% |
| Hodgdon H4831 SC | <<locked>> | 80% | 48,573 psi | 76% | 2503 fps | 99.8% |
| Hodgdon Retumbo | <<locked>> | 80% | 39,885 psi | 63% | 2484 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,572 psi | 45% | 1457 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 50,024 psi | 78% | 2497 fps | 99.9% |
| IMR 7828 SSC | <<locked>> | 80% | 45,890 psi | 72% | 2513 fps | 99.9% |
| IMR 7977 Enduron | <<locked>> | 84% | 45,614 psi | 71% | 2408 fps | 95.3% |
| IMR 8133 Enduron | <<locked>> | 80% | 30,182 psi | 47% | 2224 fps | 96.9% |
| Lovex D100 | <<locked>> | 92% | 51,750 psi | 81% | 2552 fps | 95.8% |
| Lovex S071 | <<locked>> | 80% | 41,234 psi | 65% | 2336 fps | 100% |
| Norma 217 | <<locked>> | 80% | 30,458 psi | 48% | 2244 fps | 98.9% |
| Norma MRP | <<locked>> | 80% | 50,937 psi | 80% | 2585 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 46,528 psi | 73% | 2530 fps | 100% |
| Ramshot LRT | <<locked>> | 96% | 52,750 psi | 83% | 2680 fps | 95.9% |
| Ramshot Magnum | <<locked>> | 80% | 41,713 psi | 65% | 2415 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,428 psi | 46% | 1496 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 39,146 psi | 61% | 2461 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 36,085 psi | 57% | 2375 fps | 97.8% |
| Rottweil R 904 | <<locked>> | 80% | 52,214 psi | 82% | 2530 fps | 100% |
| Rottweil R 905 | <<locked>> | 80% | 51,416 psi | 81% | 2543 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 92% | 51,750 psi | 81% | 2552 fps | 95.8% |
| SNPE Vectan SP 13 | <<locked>> | 92% | 38,798 psi | 61% | 2379 fps | 95.5% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 51,068 psi | 80% | 2539 fps | 100% |
| Somchem S361 | <<locked>> | 80% | 53,185 psi | 83% | 2526 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 51,663 psi | 81% | 2516 fps | 100% |
| Vihtavuori 24N41 | <<locked>> | 96% | 50,879 psi | 80% | 2592 fps | 95% |
| Vihtavuori N165 | <<locked>> | 80% | 45,295 psi | 71% | 2415 fps | 100% |
| Vihtavuori N170 | <<locked>> | 82% | 41,524 psi | 65% | 2385 fps | 95.8% |
| Vihtavuori N555 | <<locked>> | 80% | 51,387 psi | 81% | 2510 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 50,401 psi | 79% | 2592 fps | 100% |
| Vihtavuori N565 | <<locked>> | 80% | 42,250 psi | 66% | 2438 fps | 99.4% |
| Vihtavuori N568 | <<locked>> | 80% | 37,275 psi | 58% | 2385 fps | 97.6% |
| Vihtavuori N570 | 92.8 gr | 82% | 38,101 psi | 60% | 2438 fps | 96% |
| Winchester StaBALL HD | <<locked>> | 80% | 46,108 psi | 72% | 2523 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 47,718 psi | 75% | 2464 fps | 100% |
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 57 powders for .338-378 Weath. Mag. loaded with the .338 | 300gr | Sierra HPBT LR MatchKing. ADI AR 2218 delivers the highest muzzle velocity at 2,805 fps; across all powders the maximum-charge window runs from 1,634 fps to 2,805 fps. Accurate 8700 gives the best case fill at 100 %, and 57 of the 57 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (440 MPa), the top charges use 60–90 %, leaving at least 10 % headroom. The 300.0 gr projectile in 0.338" calls for a 1:12.0 twist; slower twists will usually not stabilise this weight. Accurate 8700, Hodgdon TrailBoss, ReloadSwiss RS 14 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. ADI AR 2218, Vihtavuori N570, Alliant Reloder-33 rank at the top here: for .338-378 Weath. Mag. with the .338 | 300gr | Sierra HPBT LR 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.