Load Specifications
Load data in caliber .338-378 Weath. Mag. with .338 | 300gr | MAKER Expanding Subsonic bullet and 55 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ADI AR 2218, Hodgdon Retumbo and Vihtavuori N570.
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>> | 86% | 56,855 psi | 89% | 2556 fps | 100% |
| Accurate 8700ᴾ | <<locked>> | 100% | 47,253 psi | 74% | 2552 fps | 98.1% |
| Accurate MAGPRO | <<locked>> | 84% | 55,840 psi | 88% | 2671 fps | 100% |
| ADI AR 2209 | <<locked>> | 82% | 54,288 psi | 85% | 2585 fps | 100% |
| ADI AR 2213 | <<locked>> | 86% | 56,536 psi | 89% | 2661 fps | 100% |
| ADI AR 2217 | <<locked>> | 94% | 55,434 psi | 87% | 2644 fps | 100% |
| ADI AR 2218 | <<locked>> | 98% | 55,361 psi | 87% | 2776 fps | 99.8% |
| ADI AR 2225 | <<locked>> | 96% | 54,418 psi | 85% | 2667 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 84% | 57,319 psi | 90% | 2625 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 86% | 57,043 psi | 89% | 2651 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 86% | 55,347 psi | 87% | 2559 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 90% | 55,680 psi | 87% | 2635 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 82% | 55,869 psi | 88% | 2644 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 96% | 57,276 psi | 90% | 2749 fps | 99.8% |
| Alliant Reloder-50ᴾ | <<locked>> | 100% | 57,058 psi | 89% | 2749 fps | 99.5% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 56,594 psi | 89% | 2628 fps | 99.7% |
| Bofors RP15 | <<locked>> | 88% | 56,420 psi | 88% | 2644 fps | 100% |
| Bofors RP30 | <<locked>> | 92% | 55,390 psi | 87% | 2661 fps | 100% |
| Bofors RP5 | <<locked>> | 86% | 57,043 psi | 89% | 2651 fps | 100% |
| Hodgdon H1000 | <<locked>> | 92% | 56,855 psi | 89% | 2661 fps | 100% |
| Hodgdon H4831 | <<locked>> | 84% | 55,317 psi | 87% | 2595 fps | 100% |
| Hodgdon H4831 SC | <<locked>> | 84% | 54,317 psi | 85% | 2582 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 90% | 54,998 psi | 86% | 2723 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 38,043 psi | 60% | 1624 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 84% | 55,651 psi | 87% | 2572 fps | 100% |
| IMR 7828 SSC | <<locked>> | 86% | 55,100 psi | 86% | 2644 fps | 100% |
| IMR 7977 Enduron | <<locked>> | 92% | 57,696 psi | 90% | 2585 fps | 97.7% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 57,188 psi | 90% | 2707 fps | 100% |
| Lovex D100 | <<locked>> | 94% | 54,201 psi | 85% | 2582 fps | 96.2% |
| Lovex S071 | <<locked>> | 90% | 55,129 psi | 86% | 2536 fps | 100% |
| Norma 217 | <<locked>> | 98% | 54,839 psi | 86% | 2674 fps | 100% |
| Norma MRP | <<locked>> | 84% | 57,101 psi | 89% | 2664 fps | 100% |
| Ramshot Grand | <<locked>> | 86% | 56,260 psi | 88% | 2664 fps | 100% |
| Ramshot LRT | <<locked>> | 98% | 55,071 psi | 86% | 2707 fps | 96.2% |
| Ramshot Magnum | <<locked>> | 88% | 54,578 psi | 86% | 2602 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 39,088 psi | 61% | 1663 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 90% | 55,521 psi | 87% | 2710 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 92% | 54,563 psi | 86% | 2690 fps | 100% |
| Rottweil R 904 | <<locked>> | 82% | 54,665 psi | 86% | 2559 fps | 100% |
| Rottweil R 905 | <<locked>> | 84% | 57,363 psi | 90% | 2618 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 94% | 54,201 psi | 85% | 2582 fps | 96.2% |
| SNPE Vectan SP 13ᴾ | <<locked>> | 100% | 49,414 psi | 77% | 2562 fps | 98.2% |
| SNPE Vectan Tubal 8000 | <<locked>> | 84% | 57,014 psi | 89% | 2615 fps | 100% |
| Somchem S361 | <<locked>> | 82% | 55,738 psi | 87% | 2552 fps | 100% |
| Somchem S385 | <<locked>> | 84% | 57,493 psi | 90% | 2589 fps | 100% |
| Vihtavuori 24N41ᴾ | <<locked>> | 100% | 57,159 psi | 90% | 2680 fps | 96.3% |
| Vihtavuori N165 | <<locked>> | 88% | 57,493 psi | 90% | 2579 fps | 100% |
| Vihtavuori N170 | <<locked>> | 92% | 56,521 psi | 89% | 2625 fps | 98.8% |
| Vihtavuori N555 | <<locked>> | 84% | 57,159 psi | 90% | 2582 fps | 100% |
| Vihtavuori N560 | <<locked>> | 84% | 56,420 psi | 88% | 2674 fps | 100% |
| Vihtavuori N565 | <<locked>> | 90% | 57,493 psi | 90% | 2674 fps | 100% |
| Vihtavuori N568 | <<locked>> | 92% | 55,245 psi | 87% | 2690 fps | 100% |
| Vihtavuori N570 | <<locked>> | 94% | 56,608 psi | 89% | 2756 fps | 99.6% |
| Winchester StaBALL HD | <<locked>> | 86% | 55,680 psi | 87% | 2648 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 86% | 57,334 psi | 90% | 2592 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% | 46,659 psi | 73% | 2418 fps | 100% |
| Accurate 8700 | <<locked>> | 94% | 38,232 psi | 60% | 2385 fps | 95.6% |
| Accurate MAGPRO | <<locked>> | 80% | 48,646 psi | 76% | 2562 fps | 99.7% |
| ADI AR 2209 | <<locked>> | 80% | 50,691 psi | 79% | 2536 fps | 100% |
| ADI AR 2213 | <<locked>> | 80% | 45,948 psi | 72% | 2503 fps | 99.9% |
| ADI AR 2217 | <<locked>> | 80% | 34,418 psi | 54% | 2287 fps | 98.3% |
| ADI AR 2218 | 97.2 gr | 86% | 36,027 psi | 56% | 2402 fps | 95.1% |
| ADI AR 2225 | <<locked>> | 80% | 31,720 psi | 50% | 2267 fps | 99.7% |
| Alliant Reloder-19 | <<locked>> | 80% | 50,531 psi | 79% | 2530 fps | 100% |
| Alliant Reloder-22 | <<locked>> | 80% | 46,717 psi | 73% | 2503 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 80% | 45,643 psi | 72% | 2428 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 39,682 psi | 62% | 2398 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 80% | 51,938 psi | 81% | 2592 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 84% | 36,898 psi | 58% | 2402 fps | 95.8% |
| Alliant Reloder-50 | <<locked>> | 88% | 36,796 psi | 58% | 2395 fps | 95.2% |
| Baschieri & Pellagri 109 | <<locked>> | 80% | 43,743 psi | 69% | 2425 fps | 97.9% |
| Bofors RP15 | <<locked>> | 80% | 43,598 psi | 68% | 2448 fps | 99.9% |
| Bofors RP30 | <<locked>> | 80% | 37,115 psi | 58% | 2356 fps | 99% |
| Bofors RP5 | <<locked>> | 80% | 46,717 psi | 73% | 2503 fps | 100% |
| Hodgdon H1000 | <<locked>> | 80% | 37,333 psi | 59% | 2349 fps | 99.4% |
| Hodgdon H4831 | <<locked>> | 80% | 48,428 psi | 76% | 2493 fps | 99.8% |
| Hodgdon H4831 SC | <<locked>> | 80% | 47,543 psi | 75% | 2480 fps | 99.7% |
| Hodgdon Retumbo | 85.4 gr | 80% | 38,885 psi | 61% | 2461 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 28,558 psi | 45% | 1450 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 49,023 psi | 77% | 2474 fps | 99.9% |
| IMR 7828 SSC | <<locked>> | 80% | 44,875 psi | 70% | 2490 fps | 99.8% |
| IMR 7977 Enduron | <<locked>> | 86% | 47,703 psi | 75% | 2434 fps | 95.6% |
| IMR 8133 Enduron | <<locked>> | 80% | 29,341 psi | 46% | 2198 fps | 96.4% |
| Lovex D100 | <<locked>> | 92% | 50,618 psi | 79% | 2530 fps | 95.3% |
| Lovex S071 | <<locked>> | 80% | 40,408 psi | 63% | 2316 fps | 100% |
| Norma 217 | <<locked>> | 80% | 29,573 psi | 46% | 2221 fps | 98.6% |
| Norma MRP | <<locked>> | 80% | 49,806 psi | 78% | 2562 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 45,353 psi | 71% | 2507 fps | 99.9% |
| Ramshot LRT | <<locked>> | 96% | 51,285 psi | 80% | 2648 fps | 95.3% |
| Ramshot Magnum | <<locked>> | 80% | 40,698 psi | 64% | 2392 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 29,428 psi | 46% | 1486 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 80% | 38,130 psi | 60% | 2438 fps | 100% |
| ReloadSwiss RS 80 | <<locked>> | 80% | 34,998 psi | 55% | 2349 fps | 97.3% |
| Rottweil R 904 | <<locked>> | 80% | 51,285 psi | 80% | 2510 fps | 100% |
| Rottweil R 905 | <<locked>> | 80% | 50,401 psi | 79% | 2523 fps | 100% |
| Shooters World 50 BMG | <<locked>> | 92% | 50,618 psi | 79% | 2530 fps | 95.3% |
| SNPE Vectan SP 13 | <<locked>> | 92% | 37,811 psi | 59% | 2352 fps | 95% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 50,053 psi | 78% | 2520 fps | 100% |
| Somchem S361 | <<locked>> | 80% | 52,156 psi | 82% | 2503 fps | 99.9% |
| Somchem S385 | <<locked>> | 80% | 50,589 psi | 79% | 2493 fps | 100% |
| Vihtavuori 24N41 | <<locked>> | 98% | 53,359 psi | 84% | 2625 fps | 95.5% |
| Vihtavuori N165 | <<locked>> | 80% | 44,425 psi | 70% | 2395 fps | 100% |
| Vihtavuori N170 | <<locked>> | 82% | 40,553 psi | 64% | 2359 fps | 95.3% |
| Vihtavuori N555 | <<locked>> | 80% | 50,299 psi | 79% | 2493 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 49,313 psi | 77% | 2569 fps | 99.9% |
| Vihtavuori N565 | <<locked>> | 80% | 41,234 psi | 65% | 2415 fps | 99.2% |
| Vihtavuori N568 | <<locked>> | 80% | 36,303 psi | 57% | 2362 fps | 97.2% |
| Vihtavuori N570 | 90.8 gr | 82% | 36,999 psi | 58% | 2408 fps | 95.4% |
| Winchester StaBALL HD | <<locked>> | 80% | 44,744 psi | 70% | 2500 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 46,702 psi | 73% | 2441 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 58 powders for .338-378 Weath. Mag. loaded with the .338 | 300gr | MAKER Expanding Subsonic. ADI AR 2218 delivers the highest muzzle velocity at 2,776 fps; across all powders the maximum-charge window runs from 1,624 fps to 2,776 fps. Accurate 8700 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 60–90 %, leaving at least 10 % headroom. The 300.0 gr projectile in 0.338" calls for a 1:11.5 twist; slower twists will usually not stabilise this weight. Accurate 8700, Alliant Reloder-50, Hodgdon TrailBoss 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, Hodgdon Retumbo, Vihtavuori N570 rank at the top here: for .338-378 Weath. Mag. with the .338 | 300gr | MAKER Expanding Subsonic they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Hodgdon 50BMG, Vihtavuori 20N29 burn incompletely and react more sensitively to barrel length and temperature. Always begin at the start load and work up in small increments while checking case and primer for pressure signs.