Load Specifications
Load data in caliber .338-378 Weath. Mag. with .338 | 225gr | Hornady GMX bullet and 74 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Hodgdon Retumbo, ReloadSwiss RS 76 and Accurate MAGPRO.
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>> | 92% | 56,333 psi | 88% | 2930 fps | 100% |
| Accurate 4350 | <<locked>> | 84% | 57,203 psi | 90% | 2956 fps | 100% |
| Accurate MAGPRO | <<locked>> | 90% | 55,230 psi | 87% | 3035 fps | 98.9% |
| ADI AR 2209 | <<locked>> | 88% | 54,621 psi | 86% | 2969 fps | 99.9% |
| ADI AR 2213 | <<locked>> | 92% | 56,434 psi | 88% | 3038 fps | 99.6% |
| ADI AR 2217ᴾ | <<locked>> | 100% | 54,331 psi | 85% | 3002 fps | 99.7% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 48,733 psi | 76% | 2963 fps | 100% |
| Alliant Power Pro Varmint | <<locked>> | 88% | 54,752 psi | 86% | 2966 fps | 99.9% |
| Alliant Reloder-16 | <<locked>> | 84% | 54,853 psi | 86% | 2963 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 88% | 54,128 psi | 85% | 2959 fps | 99.8% |
| Alliant Reloder-22 | <<locked>> | 92% | 56,565 psi | 89% | 3031 fps | 100% |
| Alliant Reloder-23 | <<locked>> | 92% | 54,201 psi | 85% | 2940 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 96% | 53,954 psi | 85% | 3009 fps | 100% |
| Alliant Reloder-26 | <<locked>> | 88% | 54,549 psi | 85% | 3025 fps | 100% |
| Alliant Reloder-33ᴾ | <<locked>> | 100% | 51,169 psi | 80% | 3018 fps | 96.8% |
| Baschieri & Pellagri 109 | <<locked>> | 94% | 57,464 psi | 90% | 2995 fps | 98% |
| Bofors RP15 | <<locked>> | 94% | 55,579 psi | 87% | 3018 fps | 99.9% |
| Bofors RP30ᴾ | <<locked>> | 100% | 57,406 psi | 90% | 3071 fps | 99.9% |
| Bofors RP5 | <<locked>> | 92% | 56,565 psi | 89% | 3031 fps | 100% |
| Bofors RP7 | <<locked>> | 82% | 55,361 psi | 87% | 2904 fps | 100% |
| Hodgdon H1000 | <<locked>> | 98% | 56,115 psi | 88% | 3028 fps | 99.9% |
| Hodgdon H414 | <<locked>> | 82% | 55,056 psi | 86% | 2959 fps | 100% |
| Hodgdon H4350 | <<locked>> | 82% | 57,609 psi | 90% | 2976 fps | 100% |
| Hodgdon H4831 | <<locked>> | 90% | 55,985 psi | 88% | 2972 fps | 99.2% |
| Hodgdon H4831 SC | <<locked>> | 90% | 54,795 psi | 86% | 2953 fps | 99.1% |
| Hodgdon Hybrid 100V | <<locked>> | 86% | 54,926 psi | 86% | 2881 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 98% | 56,695 psi | 89% | 3146 fps | 100% |
| Hodgdon Superformance | <<locked>> | 82% | 55,869 psi | 88% | 2999 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 37,289 psi | 58% | 1870 fps | 100% |
| IMR 4350 | <<locked>> | 86% | 57,406 psi | 90% | 2949 fps | 100% |
| IMR 4451 Enduron | <<locked>> | 82% | 56,855 psi | 89% | 2927 fps | 100% |
| IMR 4831 | <<locked>> | 86% | 57,595 psi | 90% | 2946 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 90% | 56,695 psi | 89% | 2953 fps | 99.4% |
| IMR 7828 SSC | <<locked>> | 92% | 54,418 psi | 85% | 3015 fps | 99.5% |
| IMR 8133 Enduronᴾ | <<locked>> | 100% | 44,164 psi | 69% | 2864 fps | 98.3% |
| Lovex S065 | <<locked>> | 84% | 57,609 psi | 90% | 2923 fps | 100% |
| Lovex S070 | <<locked>> | 84% | 55,883 psi | 88% | 2923 fps | 100% |
| Lovex S071 | <<locked>> | 98% | 57,580 psi | 90% | 2946 fps | 100% |
| Norma 204 | <<locked>> | 84% | 54,766 psi | 86% | 2949 fps | 99.8% |
| Norma 217ᴾ | <<locked>> | 100% | 44,512 psi | 70% | 2890 fps | 99.7% |
| Norma MRP | <<locked>> | 90% | 56,594 psi | 89% | 3051 fps | 100% |
| Norma URP | <<locked>> | 84% | 55,622 psi | 87% | 2940 fps | 100% |
| Ramshot Grand | <<locked>> | 92% | 55,303 psi | 87% | 3038 fps | 99.8% |
| Ramshot Hunter | <<locked>> | 84% | 54,534 psi | 85% | 2946 fps | 100% |
| Ramshot Magnum | <<locked>> | 94% | 53,722 psi | 84% | 2966 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 38,101 psi | 60% | 1913 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 84% | 57,421 psi | 90% | 2979 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 84% | 56,159 psi | 88% | 3015 fps | 100% |
| ReloadSwiss RS 76 | <<locked>> | 96% | 53,447 psi | 84% | 3077 fps | 100% |
| ReloadSwiss RS 80ᴾ | <<locked>> | 100% | 56,884 psi | 89% | 3100 fps | 99.4% |
| Rottweil R 904 | <<locked>> | 88% | 55,419 psi | 87% | 2940 fps | 99.5% |
| Rottweil R 905 | <<locked>> | 90% | 57,435 psi | 90% | 3005 fps | 100% |
| Rottweil R 907 | <<locked>> | 82% | 55,361 psi | 87% | 2904 fps | 100% |
| Shooters World Long Rifle | <<locked>> | 84% | 57,609 psi | 90% | 2923 fps | 100% |
| Shooters World SW4350 | <<locked>> | 84% | 55,883 psi | 88% | 2923 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 84% | 56,710 psi | 89% | 2877 fps | 100% |
| SNPE Vectan Tubal 8000 | <<locked>> | 90% | 57,000 psi | 89% | 3002 fps | 100% |
| Somchem S361 | <<locked>> | 88% | 57,058 psi | 89% | 2930 fps | 99.3% |
| Somchem S365 | <<locked>> | 86% | 56,550 psi | 89% | 2940 fps | 100% |
| Somchem S385 | <<locked>> | 90% | 57,725 psi | 90% | 2969 fps | 100% |
| Vihtavuori N150 | <<locked>> | 82% | 57,653 psi | 90% | 2858 fps | 100% |
| Vihtavuori N160 | <<locked>> | 84% | 57,334 psi | 90% | 2930 fps | 100% |
| Vihtavuori N165 | <<locked>> | 94% | 57,624 psi | 90% | 2956 fps | 100% |
| Vihtavuori N170 | <<locked>> | 98% | 56,318 psi | 88% | 2966 fps | 96.1% |
| Vihtavuori N550 | <<locked>> | 84% | 56,434 psi | 88% | 2936 fps | 100% |
| Vihtavuori N555 | <<locked>> | 90% | 56,246 psi | 88% | 2966 fps | 100% |
| Vihtavuori N560 | <<locked>> | 90% | 56,246 psi | 88% | 3051 fps | 99.4% |
| Vihtavuori N565 | <<locked>> | 96% | 56,376 psi | 88% | 3031 fps | 99.5% |
| Vihtavuori N568ᴾ | <<locked>> | 100% | 57,667 psi | 90% | 3100 fps | 99.1% |
| Vihtavuori N570ᴾ | <<locked>> | 100% | 54,520 psi | 85% | 3094 fps | 97.2% |
| Winchester 6.5 StaBALL | <<locked>> | 84% | 56,956 psi | 89% | 2881 fps | 100% |
| Winchester 760 | <<locked>> | 82% | 55,216 psi | 87% | 2963 fps | 100% |
| Winchester StaBALL HD | <<locked>> | 94% | 57,101 psi | 89% | 3081 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 90% | 53,940 psi | 85% | 2913 fps | 99.8% |
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% | 37,086 psi | 58% | 2595 fps | 99.1% |
| Accurate 4350 | <<locked>> | 80% | 49,719 psi | 78% | 2844 fps | 100% |
| Accurate MAGPRO | 96.7 gr | 82% | 41,365 psi | 65% | 2776 fps | 95.9% |
| ADI AR 2209 | <<locked>> | 80% | 41,553 psi | 65% | 2733 fps | 98.1% |
| ADI AR 2213 | <<locked>> | 80% | 36,999 psi | 58% | 2661 fps | 95.5% |
| ADI AR 2217 | <<locked>> | 88% | 35,984 psi | 56% | 2635 fps | 95.5% |
| ADI AR 2225 | <<locked>> | 84% | 28,340 psi | 44% | 2467 fps | 95% |
| Alliant Power Pro Varmint | <<locked>> | 80% | 41,843 psi | 66% | 2733 fps | 98.2% |
| Alliant Reloder-16 | <<locked>> | 80% | 47,834 psi | 75% | 2854 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 80% | 41,466 psi | 65% | 2726 fps | 98.1% |
| Alliant Reloder-22 | <<locked>> | 80% | 37,318 psi | 58% | 2671 fps | 97.1% |
| Alliant Reloder-23 | <<locked>> | 80% | 35,998 psi | 56% | 2621 fps | 100% |
| Alliant Reloder-25 | <<locked>> | 80% | 31,096 psi | 49% | 2543 fps | 98.2% |
| Alliant Reloder-26 | <<locked>> | 80% | 40,089 psi | 63% | 2776 fps | 100% |
| Alliant Reloder-33 | <<locked>> | 98% | 47,398 psi | 74% | 2946 fps | 95.8% |
| Baschieri & Pellagri 109 | <<locked>> | 88% | 47,543 psi | 75% | 2822 fps | 95.8% |
| Bofors RP15 | <<locked>> | 80% | 34,693 psi | 54% | 2602 fps | 96% |
| Bofors RP30 | <<locked>> | 86% | 35,186 psi | 55% | 2644 fps | 95.6% |
| Bofors RP5 | <<locked>> | 80% | 37,318 psi | 58% | 2671 fps | 97.1% |
| Bofors RP7 | <<locked>> | 80% | 51,866 psi | 81% | 2848 fps | 99.9% |
| Hodgdon H1000 | <<locked>> | 84% | 34,171 psi | 54% | 2592 fps | 95.4% |
| Hodgdon H414 | <<locked>> | 80% | 51,576 psi | 81% | 2904 fps | 100% |
| Hodgdon H4350 | <<locked>> | 80% | 53,882 psi | 84% | 2917 fps | 99.9% |
| Hodgdon H4831 | <<locked>> | 80% | 39,537 psi | 62% | 2667 fps | 95.8% |
| Hodgdon H4831 SC | <<locked>> | 80% | 38,812 psi | 61% | 2651 fps | 95.5% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 45,034 psi | 71% | 2730 fps | 100% |
| Hodgdon Retumbo | 91.5 gr | 82% | 32,518 psi | 51% | 2631 fps | 96% |
| Hodgdon Superformance | <<locked>> | 80% | 51,793 psi | 81% | 2933 fps | 100% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,891 psi | 44% | 1673 fps | 100% |
| IMR 4350 | <<locked>> | 80% | 47,384 psi | 74% | 2785 fps | 99.7% |
| IMR 4451 Enduron | <<locked>> | 80% | 53,359 psi | 84% | 2874 fps | 100% |
| IMR 4831 | <<locked>> | 80% | 47,268 psi | 74% | 2792 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 80% | 41,104 psi | 64% | 2671 fps | 96.4% |
| IMR 7828 SSC | <<locked>> | 80% | 35,621 psi | 56% | 2638 fps | 95.1% |
| IMR 8133 Enduron | <<locked>> | 94% | 35,839 psi | 56% | 2680 fps | 95.7% |
| Lovex S065 | <<locked>> | 80% | 50,720 psi | 79% | 2818 fps | 100% |
| Lovex S070 | <<locked>> | 80% | 49,139 psi | 77% | 2815 fps | 99.9% |
| Lovex S071 | <<locked>> | 80% | 31,807 psi | 50% | 2467 fps | 97.7% |
| Norma 204 | <<locked>> | 80% | 47,674 psi | 75% | 2831 fps | 99.1% |
| Norma 217 | <<locked>> | 90% | 31,241 psi | 49% | 2582 fps | 96.1% |
| Norma MRP | <<locked>> | 80% | 39,349 psi | 62% | 2740 fps | 98.8% |
| Norma URP | <<locked>> | 80% | 48,718 psi | 76% | 2835 fps | 100% |
| Ramshot Grand | <<locked>> | 80% | 35,186 psi | 55% | 2641 fps | 95.3% |
| Ramshot Hunter | <<locked>> | 80% | 47,587 psi | 75% | 2835 fps | 100% |
| Ramshot Magnum | <<locked>> | 80% | 31,401 psi | 49% | 2520 fps | 95.8% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 28,558 psi | 45% | 1713 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 49,980 psi | 78% | 2867 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 48,356 psi | 76% | 2894 fps | 100% |
| ReloadSwiss RS 76 | 95.5 gr | 80% | 29,298 psi | 46% | 2526 fps | 95.5% |
| ReloadSwiss RS 80 | <<locked>> | 90% | 38,450 psi | 60% | 2753 fps | 95.2% |
| Rottweil R 904 | <<locked>> | 80% | 42,714 psi | 67% | 2710 fps | 97.4% |
| Rottweil R 905 | <<locked>> | 80% | 40,915 psi | 64% | 2713 fps | 98.2% |
| Rottweil R 907 | <<locked>> | 80% | 51,866 psi | 81% | 2848 fps | 99.9% |
| Shooters World Long Rifle | <<locked>> | 80% | 50,720 psi | 79% | 2818 fps | 100% |
| Shooters World SW4350 | <<locked>> | 80% | 49,139 psi | 77% | 2815 fps | 99.9% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 49,603 psi | 78% | 2769 fps | 99.9% |
| SNPE Vectan Tubal 8000 | <<locked>> | 80% | 40,582 psi | 64% | 2707 fps | 98% |
| Somchem S361 | <<locked>> | 80% | 43,439 psi | 68% | 2697 fps | 96.9% |
| Somchem S365 | <<locked>> | 80% | 46,035 psi | 72% | 2785 fps | 100% |
| Somchem S385 | <<locked>> | 80% | 41,321 psi | 65% | 2690 fps | 98.8% |
| Vihtavuori N150 | <<locked>> | 80% | 54,027 psi | 85% | 2808 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 50,111 psi | 79% | 2822 fps | 100% |
| Vihtavuori N165 | <<locked>> | 80% | 35,839 psi | 56% | 2562 fps | 97.2% |
| Vihtavuori N170 | <<locked>> | 96% | 52,562 psi | 82% | 2904 fps | 95.2% |
| Vihtavuori N550 | <<locked>> | 80% | 49,458 psi | 78% | 2828 fps | 100% |
| Vihtavuori N555 | <<locked>> | 80% | 40,205 psi | 63% | 2700 fps | 100% |
| Vihtavuori N560 | <<locked>> | 80% | 39,349 psi | 62% | 2733 fps | 95.9% |
| Vihtavuori N565 | <<locked>> | 84% | 37,028 psi | 58% | 2661 fps | 95.4% |
| Vihtavuori N568 | <<locked>> | 90% | 39,856 psi | 62% | 2769 fps | 95% |
| Vihtavuori N570 | <<locked>> | 96% | 46,934 psi | 74% | 2956 fps | 95.2% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 49,487 psi | 78% | 2779 fps | 100% |
| Winchester 760 | <<locked>> | 80% | 51,721 psi | 81% | 2907 fps | 100% |
| Winchester StaBALL HD | <<locked>> | 80% | 32,663 psi | 51% | 2657 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 80% | 37,942 psi | 59% | 2618 fps | 97.3% |
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 74 powders for .338-378 Weath. Mag. loaded with the .338 | 225gr | Hornady GMX. Hodgdon Retumbo delivers the highest muzzle velocity at 3,146 fps; across all powders the maximum-charge window runs from 1,870 fps to 3,146 fps. ADI AR 2217 gives the best case fill at 100 %, and 74 of the 74 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (440 MPa), the top charges use 58–90 %, leaving at least 10 % headroom. The 225.0 gr projectile in 0.338" calls for a 1:12.0 twist; slower twists will usually not stabilise this weight. ADI AR 2217, ADI AR 2225, Alliant Reloder-33 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. Hodgdon Retumbo, ReloadSwiss RS 76, Accurate MAGPRO rank at the top here: for .338-378 Weath. Mag. with the .338 | 225gr | Hornady GMX 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.