Load Specifications
Load data in caliber .378 Weath. Mag. with .375 | 270gr | Atomic 29 HP bullet and 96 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant Reloder-26, Norma MRP and Vihtavuori N560.
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 2495 | <<locked>> | 82% | 55,651 psi | 87% | 2756 fps | 100% |
| Accurate 2700 | <<locked>> | 84% | 57,188 psi | 90% | 2844 fps | 99.5% |
| Accurate 3100ᴾ | <<locked>> | 100% | 55,187 psi | 86% | 2887 fps | 100% |
| Accurate 4064 | <<locked>> | 84% | 56,130 psi | 88% | 2815 fps | 100% |
| Accurate 4350 | <<locked>> | 92% | 57,566 psi | 90% | 2936 fps | 100% |
| Accurate MAGPRO | <<locked>> | 98% | 53,896 psi | 84% | 2982 fps | 97% |
| ADI AR 2208 | <<locked>> | 86% | 56,521 psi | 89% | 2854 fps | 100% |
| ADI AR 2209 | <<locked>> | 96% | 54,839 psi | 86% | 2933 fps | 98.9% |
| ADI AR 2213ᴾ | <<locked>> | 100% | 56,202 psi | 88% | 2989 fps | 98.2% |
| ADI AR 2225ᴾ | <<locked>> | 100% | 35,723 psi | 56% | 2638 fps | 96.1% |
| Alliant Power Pro 2000-MR | <<locked>> | 82% | 56,217 psi | 88% | 2986 fps | 100% |
| Alliant Reloder- TS 15.5 | <<locked>> | 86% | 57,363 psi | 90% | 2874 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 84% | 57,638 psi | 90% | 2900 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 92% | 54,824 psi | 86% | 2943 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 88% | 56,072 psi | 88% | 2963 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 96% | 54,230 psi | 85% | 2920 fps | 98.9% |
| Alliant Reloder-22ᴾ | <<locked>> | 100% | 55,216 psi | 87% | 2982 fps | 99.1% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 52,199 psi | 82% | 2907 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 45,237 psi | 71% | 2844 fps | 99.8% |
| Alliant Reloder-26 | <<locked>> | 98% | 56,333 psi | 88% | 3054 fps | 100% |
| Bofors RP15ᴾ | <<locked>> | 100% | 50,589 psi | 79% | 2907 fps | 98.4% |
| Bofors RP3 | <<locked>> | 84% | 54,578 psi | 86% | 2844 fps | 100% |
| Bofors RP5ᴾ | <<locked>> | 100% | 55,216 psi | 87% | 2982 fps | 99.1% |
| Bofors RP7 | <<locked>> | 90% | 57,566 psi | 90% | 2887 fps | 99.6% |
| Hodgdon H1000ᴾ | <<locked>> | 100% | 44,860 psi | 70% | 2779 fps | 96.6% |
| Hodgdon H380 | <<locked>> | 84% | 55,056 psi | 86% | 2864 fps | 100% |
| Hodgdon H414 | <<locked>> | 90% | 55,985 psi | 88% | 2940 fps | 99.8% |
| Hodgdon H4350 | <<locked>> | 88% | 55,811 psi | 87% | 2897 fps | 99.2% |
| Hodgdon H4831 | <<locked>> | 98% | 56,362 psi | 88% | 2930 fps | 97.6% |
| Hodgdon H4831 SC | <<locked>> | 98% | 55,158 psi | 86% | 2910 fps | 97.4% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 55,013 psi | 86% | 2861 fps | 100% |
| Hodgdon LEVERevolution | <<locked>> | 82% | 56,463 psi | 88% | 2894 fps | 100% |
| Hodgdon Retumboᴾ | <<locked>> | 100% | 44,179 psi | 69% | 2881 fps | 98% |
| Hodgdon Superformance | <<locked>> | 90% | 56,449 psi | 88% | 2979 fps | 99.7% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 36,448 psi | 57% | 1775 fps | 100% |
| Hodgdon VARGET | <<locked>> | 82% | 56,927 psi | 89% | 2858 fps | 100% |
| IMR 4064 | <<locked>> | 84% | 55,970 psi | 88% | 2838 fps | 100% |
| IMR 4166 Enduron | <<locked>> | 82% | 55,071 psi | 86% | 2825 fps | 99.7% |
| IMR 4350 | <<locked>> | 92% | 55,172 psi | 86% | 2871 fps | 99.5% |
| IMR 4451 Enduron | <<locked>> | 88% | 55,825 psi | 87% | 2864 fps | 99.7% |
| IMR 4831 | <<locked>> | 92% | 54,201 psi | 85% | 2874 fps | 100% |
| IMR 4895 | <<locked>> | 82% | 55,448 psi | 87% | 2877 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 96% | 54,230 psi | 85% | 2861 fps | 97.4% |
| IMR 7828 SSCᴾ | <<locked>> | 100% | 53,563 psi | 84% | 2959 fps | 97.9% |
| Lovex S060 | <<locked>> | 82% | 57,421 psi | 90% | 2818 fps | 100% |
| Lovex S062 | <<locked>> | 84% | 56,086 psi | 88% | 2828 fps | 100% |
| Lovex S065 | <<locked>> | 90% | 55,825 psi | 87% | 2858 fps | 100% |
| Lovex S070 | <<locked>> | 92% | 57,203 psi | 90% | 2900 fps | 99.9% |
| Lovex S071ᴾ | <<locked>> | 100% | 45,701 psi | 72% | 2740 fps | 99.3% |
| Norma 201 | <<locked>> | 82% | 57,334 psi | 90% | 2838 fps | 100% |
| Norma 203B | <<locked>> | 84% | 56,913 psi | 89% | 2887 fps | 100% |
| Norma 204 | <<locked>> | 92% | 56,028 psi | 88% | 2927 fps | 98.9% |
| Norma MRP | <<locked>> | 98% | 54,868 psi | 86% | 3009 fps | 99.8% |
| Norma URP | <<locked>> | 92% | 56,202 psi | 88% | 2923 fps | 100% |
| Ramshot Big Game | <<locked>> | 82% | 54,128 psi | 85% | 2861 fps | 100% |
| Ramshot Grandᴾ | <<locked>> | 100% | 54,027 psi | 85% | 2979 fps | 98.3% |
| Ramshot Hunter | <<locked>> | 92% | 54,940 psi | 86% | 2927 fps | 100% |
| Ramshot Magnumᴾ | <<locked>> | 100% | 48,182 psi | 76% | 2851 fps | 98.7% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 37,101 psi | 58% | 1814 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 84% | 54,868 psi | 86% | 2848 fps | 99.8% |
| ReloadSwiss RS 60 | <<locked>> | 86% | 55,506 psi | 87% | 2953 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 92% | 57,464 psi | 90% | 2963 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 92% | 56,086 psi | 88% | 2995 fps | 100% |
| ReloadSwiss RS 76ᴾ | <<locked>> | 100% | 44,164 psi | 69% | 2874 fps | 98.9% |
| Rottweil R 902 | <<locked>> | 82% | 54,491 psi | 85% | 2789 fps | 100% |
| Rottweil R 903 | <<locked>> | 86% | 54,607 psi | 86% | 2838 fps | 100% |
| Rottweil R 904 | <<locked>> | 96% | 56,507 psi | 89% | 2904 fps | 98.2% |
| Rottweil R 905 | <<locked>> | 98% | 57,203 psi | 90% | 2966 fps | 99.3% |
| Rottweil R 907 | <<locked>> | 90% | 57,566 psi | 90% | 2887 fps | 99.6% |
| Shooters World Long Rifle | <<locked>> | 90% | 55,825 psi | 87% | 2858 fps | 100% |
| Shooters World Precision | <<locked>> | 84% | 56,086 psi | 88% | 2828 fps | 100% |
| Shooters World SW4350 | <<locked>> | 92% | 57,203 psi | 90% | 2900 fps | 99.9% |
| SNPE Vectan SP 11 | <<locked>> | 86% | 56,492 psi | 89% | 2900 fps | 100% |
| SNPE Vectan SP 9 | <<locked>> | 82% | 57,319 psi | 90% | 2871 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 86% | 55,796 psi | 87% | 2720 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 90% | 55,405 psi | 87% | 2812 fps | 99.7% |
| SNPE Vectan Tubal 8000 | <<locked>> | 98% | 56,724 psi | 89% | 2959 fps | 99.2% |
| Somchem S355 | <<locked>> | 86% | 54,636 psi | 86% | 2835 fps | 100% |
| Somchem S361 | <<locked>> | 94% | 54,650 psi | 86% | 2841 fps | 97.2% |
| Somchem S365 | <<locked>> | 94% | 55,709 psi | 87% | 2920 fps | 100% |
| Somchem S385 | <<locked>> | 98% | 57,653 psi | 90% | 2936 fps | 99.7% |
| Vihtavuori N135 | <<locked>> | 82% | 55,085 psi | 86% | 2746 fps | 100% |
| Vihtavuori N140 | <<locked>> | 82% | 55,187 psi | 86% | 2762 fps | 100% |
| Vihtavuori N150 | <<locked>> | 88% | 56,072 psi | 88% | 2808 fps | 100% |
| Vihtavuori N160 | <<locked>> | 90% | 54,679 psi | 86% | 2864 fps | 100% |
| Vihtavuori N165ᴾ | <<locked>> | 100% | 53,301 psi | 84% | 2858 fps | 99.1% |
| Vihtavuori N540 | <<locked>> | 84% | 57,029 psi | 89% | 2808 fps | 100% |
| Vihtavuori N550 | <<locked>> | 92% | 57,319 psi | 90% | 2920 fps | 100% |
| Vihtavuori N555 | <<locked>> | 98% | 54,549 psi | 85% | 2930 fps | 100% |
| Vihtavuori N560 | <<locked>> | 98% | 55,114 psi | 86% | 3002 fps | 97.8% |
| Vihtavuori N565ᴾ | <<locked>> | 100% | 46,818 psi | 73% | 2844 fps | 96.3% |
| Winchester 6.5 StaBALL | <<locked>> | 90% | 54,201 psi | 85% | 2828 fps | 100% |
| Winchester 760 | <<locked>> | 90% | 56,144 psi | 88% | 2943 fps | 99.8% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 47,572 psi | 75% | 2976 fps | 100% |
| Winchester StaBALL Match | <<locked>> | 82% | 57,537 psi | 90% | 2877 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 98% | 54,186 psi | 85% | 2877 fps | 98.8% |
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 2495 | <<locked>> | 80% | 51,967 psi | 81% | 2707 fps | 100% |
| Accurate 2700 | <<locked>> | 80% | 50,111 psi | 79% | 2733 fps | 98.7% |
| Accurate 3100 | <<locked>> | 84% | 31,691 psi | 50% | 2444 fps | 95.8% |
| Accurate 4064 | <<locked>> | 80% | 49,313 psi | 77% | 2717 fps | 100% |
| Accurate 4350 | <<locked>> | 80% | 37,724 psi | 59% | 2598 fps | 99% |
| Accurate MAGPRO | <<locked>> | 94% | 46,673 psi | 73% | 2854 fps | 95.2% |
| ADI AR 2208 | <<locked>> | 80% | 46,920 psi | 74% | 2707 fps | 100% |
| ADI AR 2209 | <<locked>> | 86% | 39,334 psi | 62% | 2641 fps | 95.4% |
| ADI AR 2213 | <<locked>> | 92% | 42,786 psi | 67% | 2743 fps | 95% |
| ADI AR 2225 | <<locked>> | 98% | 33,562 psi | 53% | 2575 fps | 95% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 52,286 psi | 82% | 2923 fps | 100% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 47,398 psi | 74% | 2726 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 80% | 50,604 psi | 79% | 2795 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 80% | 36,999 psi | 58% | 2615 fps | 99.2% |
| Alliant Reloder-17 | <<locked>> | 80% | 42,090 psi | 66% | 2740 fps | 100% |
| Alliant Reloder-19 | <<locked>> | 86% | 39,044 psi | 61% | 2638 fps | 95.5% |
| Alliant Reloder-22 | <<locked>> | 90% | 39,320 psi | 62% | 2690 fps | 95.8% |
| Alliant Reloder-23 | <<locked>> | 80% | 26,818 psi | 42% | 2365 fps | 97.3% |
| Alliant Reloder-25 | <<locked>> | 88% | 30,560 psi | 48% | 2490 fps | 95.8% |
| Alliant Reloder-26 | 93.3 gr | 80% | 28,616 psi | 45% | 2477 fps | 95.7% |
| Bofors RP15 | <<locked>> | 92% | 38,798 psi | 61% | 2674 fps | 95.4% |
| Bofors RP3 | <<locked>> | 80% | 47,718 psi | 75% | 2740 fps | 100% |
| Bofors RP5 | <<locked>> | 90% | 39,320 psi | 62% | 2690 fps | 95.8% |
| Bofors RP7 | <<locked>> | 80% | 41,843 psi | 66% | 2618 fps | 97.3% |
| Hodgdon H1000 | <<locked>> | 98% | 41,843 psi | 66% | 2717 fps | 95.6% |
| Hodgdon H380 | <<locked>> | 80% | 48,051 psi | 75% | 2753 fps | 99.9% |
| Hodgdon H414 | <<locked>> | 80% | 39,929 psi | 63% | 2651 fps | 97.4% |
| Hodgdon H4350 | <<locked>> | 80% | 42,946 psi | 67% | 2674 fps | 96.9% |
| Hodgdon H4831 | <<locked>> | 92% | 45,905 psi | 72% | 2753 fps | 95.3% |
| Hodgdon H4831 SC | <<locked>> | 92% | 44,918 psi | 70% | 2733 fps | 95% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 34,447 psi | 54% | 2503 fps | 99.5% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 52,721 psi | 83% | 2841 fps | 100% |
| Hodgdon Retumbo | <<locked>> | 96% | 38,783 psi | 61% | 2749 fps | 96.1% |
| Hodgdon Superformance | <<locked>> | 80% | 38,914 psi | 61% | 2664 fps | 96.8% |
| Hodgdon TrailBoss | <<locked>> | 80% | 27,224 psi | 43% | 1585 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 53,505 psi | 84% | 2805 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 49,371 psi | 77% | 2736 fps | 100% |
| IMR 4166 Enduron | <<locked>> | 80% | 51,648 psi | 81% | 2769 fps | 99.4% |
| IMR 4350 | <<locked>> | 80% | 37,637 psi | 59% | 2546 fps | 96.1% |
| IMR 4451 Enduron | <<locked>> | 80% | 43,424 psi | 68% | 2648 fps | 98.1% |
| IMR 4831 | <<locked>> | 80% | 36,419 psi | 57% | 2556 fps | 98.8% |
| IMR 4895 | <<locked>> | 80% | 51,909 psi | 81% | 2822 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 90% | 44,933 psi | 70% | 2697 fps | 95.2% |
| IMR 7828 SSC | <<locked>> | 94% | 43,743 psi | 69% | 2776 fps | 95.4% |
| Lovex S060 | <<locked>> | 80% | 54,041 psi | 85% | 2772 fps | 100% |
| Lovex S062 | <<locked>> | 80% | 49,516 psi | 78% | 2730 fps | 100% |
| Lovex S065 | <<locked>> | 80% | 40,712 psi | 64% | 2595 fps | 98.6% |
| Lovex S070 | <<locked>> | 80% | 38,986 psi | 61% | 2579 fps | 97.3% |
| Lovex S071 | <<locked>> | 88% | 30,763 psi | 48% | 2421 fps | 95.4% |
| Norma 201 | <<locked>> | 80% | 53,722 psi | 84% | 2785 fps | 100% |
| Norma 203B | <<locked>> | 80% | 49,951 psi | 78% | 2782 fps | 100% |
| Norma 204 | <<locked>> | 82% | 39,682 psi | 62% | 2631 fps | 95.4% |
| Norma MRP | 95.1 gr | 84% | 33,344 psi | 52% | 2575 fps | 95% |
| Norma URP | <<locked>> | 80% | 37,739 psi | 59% | 2598 fps | 98.9% |
| Ramshot Big Game | <<locked>> | 80% | 50,546 psi | 79% | 2808 fps | 100% |
| Ramshot Grand | <<locked>> | 94% | 43,468 psi | 68% | 2785 fps | 95.8% |
| Ramshot Hunter | <<locked>> | 80% | 36,622 psi | 57% | 2585 fps | 97.3% |
| Ramshot Magnum | <<locked>> | 92% | 35,781 psi | 56% | 2595 fps | 95.1% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,630 psi | 43% | 1621 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 80% | 48,080 psi | 75% | 2736 fps | 99.3% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 44,788 psi | 70% | 2789 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 37,681 psi | 59% | 2621 fps | 98.8% |
| ReloadSwiss RS 70 | <<locked>> | 80% | 36,579 psi | 57% | 2631 fps | 98.4% |
| ReloadSwiss RS 76 | <<locked>> | 94% | 35,578 psi | 56% | 2664 fps | 95.9% |
| Rottweil R 902 | <<locked>> | 80% | 51,184 psi | 80% | 2740 fps | 100% |
| Rottweil R 903 | <<locked>> | 80% | 44,860 psi | 70% | 2684 fps | 100% |
| Rottweil R 904 | <<locked>> | 88% | 43,700 psi | 68% | 2684 fps | 95.5% |
| Rottweil R 905 | <<locked>> | 86% | 38,043 psi | 60% | 2618 fps | 95.4% |
| Rottweil R 907 | <<locked>> | 80% | 41,843 psi | 66% | 2618 fps | 97.3% |
| Shooters World Long Rifle | <<locked>> | 80% | 40,712 psi | 64% | 2595 fps | 98.6% |
| Shooters World Precision | <<locked>> | 80% | 49,516 psi | 78% | 2730 fps | 100% |
| Shooters World SW4350 | <<locked>> | 80% | 38,986 psi | 61% | 2579 fps | 97.3% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 46,282 psi | 73% | 2743 fps | 100% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 53,780 psi | 84% | 2822 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 46,195 psi | 72% | 2585 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 39,842 psi | 62% | 2539 fps | 97.4% |
| SNPE Vectan Tubal 8000 | <<locked>> | 86% | 37,695 psi | 59% | 2612 fps | 95.2% |
| Somchem S355 | <<locked>> | 80% | 45,078 psi | 71% | 2684 fps | 100% |
| Somchem S361 | <<locked>> | 90% | 47,790 psi | 75% | 2730 fps | 95.8% |
| Somchem S365 | <<locked>> | 80% | 34,185 psi | 54% | 2552 fps | 100% |
| Somchem S385 | <<locked>> | 84% | 36,201 psi | 57% | 2546 fps | 95.6% |
| Vihtavuori N135 | <<locked>> | 80% | 51,619 psi | 81% | 2700 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 51,880 psi | 81% | 2717 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 43,178 psi | 68% | 2615 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 39,117 psi | 61% | 2595 fps | 99.1% |
| Vihtavuori N165 | <<locked>> | 88% | 35,621 psi | 56% | 2526 fps | 95% |
| Vihtavuori N540 | <<locked>> | 80% | 50,038 psi | 78% | 2713 fps | 100% |
| Vihtavuori N550 | <<locked>> | 80% | 38,508 psi | 60% | 2595 fps | 98.9% |
| Vihtavuori N555 | <<locked>> | 80% | 29,617 psi | 46% | 2441 fps | 97.3% |
| Vihtavuori N560 | 104.2 gr | 92% | 44,730 psi | 70% | 2812 fps | 95.3% |
| Vihtavuori N565 | <<locked>> | 98% | 43,700 psi | 68% | 2785 fps | 95.4% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 38,203 psi | 60% | 2562 fps | 100% |
| Winchester 760 | <<locked>> | 80% | 40,089 psi | 63% | 2654 fps | 97.5% |
| Winchester StaBALL HD | <<locked>> | 80% | 23,612 psi | 37% | 2339 fps | 96.1% |
| Winchester StaBALL Match | <<locked>> | 80% | 53,911 psi | 84% | 2828 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 88% | 38,043 psi | 60% | 2585 fps | 95.1% |
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 96 powders for .378 Weath. Mag. loaded with the .375 | 270gr | Atomic 29 HP. Alliant Reloder-26 delivers the highest muzzle velocity at 3,054 fps; across all powders the maximum-charge window runs from 1,775 fps to 3,054 fps. Accurate 3100 gives the best case fill at 100 %, and 96 of the 96 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (440 MPa), the top charges use 56–90 %, leaving at least 10 % headroom. The 270.0 gr projectile in 0.375" calls for a 1:17.0 twist; slower twists will usually not stabilise this weight. Accurate 3100, ADI AR 2213, ADI AR 2225 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. Alliant Reloder-26, Norma MRP, Vihtavuori N560 rank at the top here: for .378 Weath. Mag. with the .375 | 270gr | Atomic 29 HP 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.