Load Specifications
Load data in caliber .375 H&H Mag. with .375 | 250gr | Speer TBBC 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 Power Pro 2000-MR, Hodgdon CFE223 and Ramshot Big Game.
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: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 2015 | <<locked>> | 90% | 55,245 psi | 89% | 2628 fps | 100% |
| Accurate 2200 | <<locked>> | 82% | 55,245 psi | 89% | 2710 fps | 98.8% |
| Accurate 2230 | <<locked>> | 82% | 56,275 psi | 90% | 2726 fps | 99.2% |
| Accurate 2460 | <<locked>> | 86% | 53,650 psi | 86% | 2651 fps | 100% |
| Accurate 2495 | <<locked>> | 96% | 55,753 psi | 89% | 2684 fps | 100% |
| Accurate 2520 | <<locked>> | 90% | 55,013 psi | 88% | 2703 fps | 100% |
| Accurate 4064 | <<locked>> | 98% | 55,143 psi | 88% | 2720 fps | 100% |
| Accurate 4350ᴾ | <<locked>> | 100% | 43,859 psi | 70% | 2612 fps | 96.5% |
| Accurate LT-30 | <<locked>> | 84% | 55,230 psi | 89% | 2575 fps | 100% |
| Accurate LT-32 | <<locked>> | 84% | 55,637 psi | 89% | 2598 fps | 100% |
| ADI AR 2206H | <<locked>> | 92% | 53,954 psi | 87% | 2703 fps | 99.2% |
| ADI AR 2208 | <<locked>> | 98% | 54,984 psi | 88% | 2700 fps | 98.9% |
| ADI AR 2219 | <<locked>> | 84% | 55,550 psi | 89% | 2690 fps | 100% |
| ADI Benchmark 8208 | <<locked>> | 90% | 53,548 psi | 86% | 2667 fps | 99.8% |
| Alliant AR-Comp | <<locked>> | 90% | 52,953 psi | 85% | 2654 fps | 100% |
| Alliant Power Pro 1200-R | <<locked>> | 86% | 54,926 psi | 88% | 2766 fps | 99.7% |
| Alliant Power Pro 2000-MR | <<locked>> | 94% | 53,417 psi | 86% | 2805 fps | 98.7% |
| Alliant Power Pro Varmint | <<locked>> | 92% | 54,607 psi | 88% | 2717 fps | 99.6% |
| Alliant Reloder- TS 15.5 | <<locked>> | 98% | 53,954 psi | 87% | 2720 fps | 99.7% |
| Alliant Reloder-10x | <<locked>> | 86% | 55,172 psi | 88% | 2635 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 96% | 54,926 psi | 88% | 2740 fps | 99% |
| Alliant Reloder-16ᴾ | <<locked>> | 100% | 44,266 psi | 71% | 2618 fps | 96.5% |
| Alliant Reloder-17ᴾ | <<locked>> | 100% | 50,966 psi | 82% | 2769 fps | 99.3% |
| Baschieri & Pellagri 106 | <<locked>> | 84% | 54,128 psi | 87% | 2572 fps | 100% |
| Baschieri & Pellagri 107 | <<locked>> | 92% | 53,577 psi | 86% | 2717 fps | 98.4% |
| Bofors RP3 | <<locked>> | 98% | 54,360 psi | 87% | 2733 fps | 99.7% |
| Hodgdon Benchmark | <<locked>> | 90% | 55,680 psi | 89% | 2654 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 92% | 55,637 psi | 89% | 2743 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 88% | 53,795 psi | 86% | 2779 fps | 98.9% |
| Hodgdon H322 | <<locked>> | 86% | 54,172 psi | 87% | 2671 fps | 100% |
| Hodgdon H335 | <<locked>> | 86% | 55,347 psi | 89% | 2697 fps | 100% |
| Hodgdon H380 | <<locked>> | 98% | 56,101 psi | 90% | 2743 fps | 98.2% |
| Hodgdon H4895 | <<locked>> | 92% | 54,433 psi | 87% | 2717 fps | 99.6% |
| Hodgdon Hybrid 100Vᴾ | <<locked>> | 100% | 40,567 psi | 65% | 2513 fps | 97.3% |
| Hodgdon LEVERevolution | <<locked>> | 94% | 52,808 psi | 85% | 2743 fps | 99.7% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 34,447 psi | 55% | 1608 fps | 100% |
| Hodgdon VARGET | <<locked>> | 94% | 55,999 psi | 90% | 2720 fps | 99.6% |
| IMR 3031 | <<locked>> | 92% | 53,461 psi | 86% | 2707 fps | 100% |
| IMR 4064 | <<locked>> | 96% | 54,375 psi | 87% | 2684 fps | 99% |
| IMR 4166 Enduron | <<locked>> | 94% | 55,434 psi | 89% | 2664 fps | 95.8% |
| IMR 4198 | <<locked>> | 86% | 55,593 psi | 89% | 2595 fps | 100% |
| IMR 4831ᴾ | <<locked>> | 100% | 42,105 psi | 68% | 2562 fps | 96.1% |
| IMR 4895 | <<locked>> | 96% | 56,289 psi | 90% | 2769 fps | 99.5% |
| IMR 8208 XBR | <<locked>> | 90% | 53,548 psi | 86% | 2667 fps | 99.8% |
| Lovex D073.5 | <<locked>> | 86% | 53,461 psi | 86% | 2654 fps | 100% |
| Lovex D073.6 | <<locked>> | 92% | 52,866 psi | 85% | 2687 fps | 100% |
| Lovex S060 | <<locked>> | 92% | 54,491 psi | 87% | 2641 fps | 99.3% |
| Lovex S062 | <<locked>> | 96% | 53,838 psi | 86% | 2684 fps | 99.8% |
| Lovex S065ᴾ | <<locked>> | 100% | 49,632 psi | 80% | 2618 fps | 96.2% |
| Norma 200 | <<locked>> | 82% | 55,071 psi | 88% | 2608 fps | 100% |
| Norma 201 | <<locked>> | 94% | 56,130 psi | 90% | 2703 fps | 99.9% |
| Norma 202 | <<locked>> | 92% | 53,069 psi | 85% | 2664 fps | 100% |
| Norma 203B | <<locked>> | 96% | 53,983 psi | 87% | 2726 fps | 99.3% |
| Norma URPᴾ | <<locked>> | 100% | 44,295 psi | 71% | 2612 fps | 96.4% |
| Ramshot Big Game | <<locked>> | 96% | 54,520 psi | 87% | 2753 fps | 99.2% |
| Ramshot TAC | <<locked>> | 90% | 54,056 psi | 87% | 2677 fps | 97.3% |
| Ramshot Wild Boar | <<locked>> | 90% | 52,910 psi | 85% | 2694 fps | 99.1% |
| Ramshot X-Terminator | <<locked>> | 88% | 54,897 psi | 88% | 2671 fps | 99.2% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 34,766 psi | 56% | 1647 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 86% | 53,185 psi | 85% | 2654 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 96% | 53,301 psi | 85% | 2674 fps | 96.1% |
| ReloadSwiss RS 52 | <<locked>> | 94% | 54,723 psi | 88% | 2802 fps | 99% |
| ReloadSwiss RS 60ᴾ | <<locked>> | 100% | 54,520 psi | 87% | 2835 fps | 100% |
| ReloadSwiss RS 62ᴾ | <<locked>> | 100% | 43,772 psi | 70% | 2628 fps | 96% |
| Rottweil R 901 | <<locked>> | 90% | 53,940 psi | 86% | 2648 fps | 100% |
| Rottweil R 902 | <<locked>> | 94% | 53,142 psi | 85% | 2654 fps | 99.7% |
| Rottweil R 903ᴾ | <<locked>> | 100% | 53,969 psi | 87% | 2720 fps | 99.6% |
| Shooters World Long Rifleᴾ | <<locked>> | 100% | 49,632 psi | 80% | 2618 fps | 96.2% |
| Shooters World Match Rifle | <<locked>> | 92% | 52,866 psi | 85% | 2687 fps | 100% |
| Shooters World Precision | <<locked>> | 96% | 53,838 psi | 86% | 2684 fps | 99.8% |
| Shooters World Tactical Rifle | <<locked>> | 84% | 53,272 psi | 85% | 2625 fps | 99.6% |
| SNPE Vectan BA6 1/2 | <<locked>> | 82% | 55,825 psi | 90% | 2343 fps | 100% |
| SNPE Vectan SP 10 | <<locked>> | 84% | 56,057 psi | 90% | 2700 fps | 100% |
| SNPE Vectan SP 11ᴾ | <<locked>> | 100% | 55,985 psi | 90% | 2782 fps | 99.4% |
| SNPE Vectan SP 3 | <<locked>> | 86% | 56,057 psi | 90% | 2651 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 92% | 55,535 psi | 89% | 2703 fps | 98% |
| SNPE Vectan SP 9 | <<locked>> | 94% | 55,854 psi | 90% | 2726 fps | 99.4% |
| SNPE Vectan Tubal 3000 | <<locked>> | 92% | 55,071 psi | 88% | 2612 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 98% | 54,418 psi | 87% | 2602 fps | 100% |
| Somchem S321 | <<locked>> | 88% | 54,563 psi | 87% | 2700 fps | 99.9% |
| Somchem S335 | <<locked>> | 92% | 54,172 psi | 87% | 2612 fps | 100% |
| Somchem S341 | <<locked>> | 92% | 54,810 psi | 88% | 2697 fps | 99.2% |
| Somchem S355ᴾ | <<locked>> | 100% | 54,737 psi | 88% | 2723 fps | 99.6% |
| Somchem S365ᴾ | <<locked>> | 100% | 39,407 psi | 63% | 2559 fps | 98.4% |
| Vihtavuori N130 | <<locked>> | 88% | 54,969 psi | 88% | 2582 fps | 100% |
| Vihtavuori N133 | <<locked>> | 92% | 54,897 psi | 88% | 2598 fps | 100% |
| Vihtavuori N135 | <<locked>> | 96% | 55,274 psi | 89% | 2671 fps | 100% |
| Vihtavuori N140 | <<locked>> | 94% | 53,679 psi | 86% | 2648 fps | 100% |
| Vihtavuori N150ᴾ | <<locked>> | 100% | 52,852 psi | 85% | 2657 fps | 99.9% |
| Vihtavuori N160ᴾ | <<locked>> | 100% | 46,746 psi | 75% | 2615 fps | 96.8% |
| Vihtavuori N530 | <<locked>> | 90% | 54,056 psi | 87% | 2667 fps | 99.8% |
| Vihtavuori N540 | <<locked>> | 96% | 55,259 psi | 89% | 2687 fps | 100% |
| Vihtavuori N550ᴾ | <<locked>> | 100% | 45,629 psi | 73% | 2615 fps | 96.4% |
| Winchester 6.5 StaBALLᴾ | <<locked>> | 100% | 47,935 psi | 77% | 2605 fps | 98.8% |
| Winchester 748 | <<locked>> | 90% | 53,026 psi | 85% | 2710 fps | 100% |
| Winchester StaBALL Match | <<locked>> | 94% | 55,448 psi | 89% | 2736 fps | 99.6% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 2015 | <<locked>> | 80% | 40,422 psi | 65% | 2408 fps | 100% |
| Accurate 2200 | <<locked>> | 80% | 51,793 psi | 83% | 2657 fps | 98.3% |
| Accurate 2230 | <<locked>> | 80% | 52,431 psi | 84% | 2667 fps | 98.7% |
| Accurate 2460 | <<locked>> | 80% | 43,918 psi | 70% | 2500 fps | 99.8% |
| Accurate 2495 | <<locked>> | 80% | 32,909 psi | 53% | 2320 fps | 99.9% |
| Accurate 2520 | <<locked>> | 80% | 39,189 psi | 63% | 2454 fps | 99.2% |
| Accurate 4064 | <<locked>> | 80% | 31,125 psi | 50% | 2300 fps | 98.3% |
| Accurate 4350 | <<locked>> | 98% | 40,915 psi | 66% | 2559 fps | 95.7% |
| Accurate LT-30 | <<locked>> | 80% | 48,849 psi | 78% | 2487 fps | 100% |
| Accurate LT-32 | <<locked>> | 80% | 49,226 psi | 79% | 2507 fps | 100% |
| ADI AR 2206H | <<locked>> | 80% | 37,101 psi | 59% | 2405 fps | 95.9% |
| ADI AR 2208 | <<locked>> | 86% | 38,130 psi | 61% | 2408 fps | 95.3% |
| ADI AR 2219 | <<locked>> | 80% | 48,733 psi | 78% | 2595 fps | 100% |
| ADI Benchmark 8208 | <<locked>> | 80% | 39,073 psi | 63% | 2421 fps | 97.7% |
| Alliant AR-Comp | <<locked>> | 80% | 37,927 psi | 61% | 2431 fps | 100% |
| Alliant Power Pro 1200-R | <<locked>> | 80% | 45,063 psi | 72% | 2605 fps | 98.5% |
| Alliant Power Pro 2000-MR | 68.1 gr | 86% | 40,872 psi | 66% | 2572 fps | 95.7% |
| Alliant Power Pro Varmint | <<locked>> | 80% | 37,507 psi | 60% | 2418 fps | 96.7% |
| Alliant Reloder- TS 15.5 | <<locked>> | 82% | 32,576 psi | 52% | 2329 fps | 95.4% |
| Alliant Reloder-10x | <<locked>> | 80% | 45,948 psi | 74% | 2507 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 84% | 37,637 psi | 60% | 2438 fps | 95.5% |
| Alliant Reloder-16 | <<locked>> | 98% | 41,785 psi | 67% | 2569 fps | 95.8% |
| Alliant Reloder-17 | <<locked>> | 88% | 34,490 psi | 55% | 2438 fps | 95% |
| Baschieri & Pellagri 106 | <<locked>> | 80% | 47,819 psi | 77% | 2487 fps | 100% |
| Baschieri & Pellagri 107 | <<locked>> | 82% | 38,508 psi | 62% | 2451 fps | 95% |
| Bofors RP3 | <<locked>> | 82% | 31,923 psi | 51% | 2326 fps | 95.3% |
| Hodgdon Benchmark | <<locked>> | 80% | 41,205 psi | 66% | 2421 fps | 98.7% |
| Hodgdon BL-C2 | <<locked>> | 80% | 37,057 psi | 59% | 2431 fps | 97.9% |
| Hodgdon CFE223 | 64.8 gr | 80% | 40,698 psi | 65% | 2552 fps | 96.4% |
| Hodgdon H322 | <<locked>> | 80% | 44,643 psi | 72% | 2530 fps | 100% |
| Hodgdon H335 | <<locked>> | 80% | 45,208 psi | 72% | 2546 fps | 99.9% |
| Hodgdon H380 | <<locked>> | 90% | 43,076 psi | 69% | 2533 fps | 95.6% |
| Hodgdon H4895 | <<locked>> | 80% | 37,362 psi | 60% | 2418 fps | 96.6% |
| Hodgdon Hybrid 100V | <<locked>> | 96% | 35,810 psi | 57% | 2415 fps | 95.7% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 33,417 psi | 54% | 2375 fps | 95.7% |
| Hodgdon TrailBoss | <<locked>> | 80% | 25,585 psi | 41% | 1434 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 35,998 psi | 58% | 2372 fps | 96.1% |
| IMR 3031 | <<locked>> | 80% | 36,114 psi | 58% | 2425 fps | 99.9% |
| IMR 4064 | <<locked>> | 84% | 37,652 psi | 60% | 2395 fps | 95.5% |
| IMR 4166 Enduron | <<locked>> | 92% | 52,069 psi | 83% | 2612 fps | 95.1% |
| IMR 4198 | <<locked>> | 80% | 46,630 psi | 75% | 2474 fps | 100% |
| IMR 4831 | <<locked>> | 98% | 39,479 psi | 63% | 2510 fps | 95.3% |
| IMR 4895 | <<locked>> | 82% | 36,071 psi | 58% | 2415 fps | 95.7% |
| IMR 8208 XBR | <<locked>> | 80% | 39,073 psi | 63% | 2421 fps | 97.7% |
| Lovex D073.5 | <<locked>> | 80% | 43,729 psi | 70% | 2503 fps | 99.3% |
| Lovex D073.6 | <<locked>> | 80% | 35,288 psi | 57% | 2385 fps | 98.4% |
| Lovex S060 | <<locked>> | 80% | 38,014 psi | 61% | 2359 fps | 96.2% |
| Lovex S062 | <<locked>> | 80% | 32,822 psi | 53% | 2303 fps | 96% |
| Lovex S065 | <<locked>> | 98% | 46,644 psi | 75% | 2569 fps | 95.5% |
| Norma 200 | <<locked>> | 80% | 51,677 psi | 83% | 2562 fps | 100% |
| Norma 201 | <<locked>> | 80% | 36,405 psi | 58% | 2365 fps | 97.1% |
| Norma 202 | <<locked>> | 80% | 36,492 psi | 59% | 2385 fps | 99.1% |
| Norma 203B | <<locked>> | 82% | 34,664 psi | 56% | 2375 fps | 95.1% |
| Norma URP | <<locked>> | 98% | 41,495 psi | 67% | 2559 fps | 95.6% |
| Ramshot Big Game | 66.5 gr | 84% | 36,564 psi | 59% | 2434 fps | 95.4% |
| Ramshot TAC | <<locked>> | 84% | 44,512 psi | 71% | 2520 fps | 95.1% |
| Ramshot Wild Boar | <<locked>> | 80% | 37,985 psi | 61% | 2434 fps | 96.1% |
| Ramshot X-Terminator | <<locked>> | 80% | 42,380 psi | 68% | 2464 fps | 97.1% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 25,802 psi | 41% | 1470 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 80% | 43,932 psi | 70% | 2510 fps | 99.5% |
| ReloadSwiss RS 50 | <<locked>> | 94% | 49,850 psi | 80% | 2618 fps | 95.4% |
| ReloadSwiss RS 52 | <<locked>> | 84% | 38,870 psi | 62% | 2526 fps | 95.8% |
| ReloadSwiss RS 60 | <<locked>> | 82% | 30,269 psi | 49% | 2336 fps | 95.8% |
| ReloadSwiss RS 62 | <<locked>> | 98% | 41,060 psi | 66% | 2575 fps | 95.1% |
| Rottweil R 901 | <<locked>> | 80% | 40,248 psi | 65% | 2425 fps | 99.5% |
| Rottweil R 902 | <<locked>> | 80% | 34,693 psi | 56% | 2323 fps | 96.6% |
| Rottweil R 903 | <<locked>> | 86% | 34,156 psi | 55% | 2372 fps | 95.8% |
| Shooters World Long Rifle | <<locked>> | 98% | 46,644 psi | 75% | 2569 fps | 95.5% |
| Shooters World Match Rifle | <<locked>> | 80% | 35,288 psi | 57% | 2385 fps | 98.4% |
| Shooters World Precision | <<locked>> | 80% | 32,822 psi | 53% | 2303 fps | 96% |
| Shooters World Tactical Rifle | <<locked>> | 80% | 46,441 psi | 74% | 2523 fps | 98.8% |
| SNPE Vectan BA6 1/2 | <<locked>> | 80% | 53,026 psi | 85% | 2310 fps | 100% |
| SNPE Vectan SP 10 | <<locked>> | 80% | 49,081 psi | 79% | 2602 fps | 100% |
| SNPE Vectan SP 11 | <<locked>> | 86% | 35,679 psi | 57% | 2421 fps | 95.1% |
| SNPE Vectan SP 3 | <<locked>> | 80% | 46,601 psi | 75% | 2520 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 84% | 42,221 psi | 68% | 2487 fps | 95.1% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 35,752 psi | 57% | 2375 fps | 95.4% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 38,174 psi | 61% | 2343 fps | 99.3% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 31,227 psi | 50% | 2215 fps | 98.7% |
| Somchem S321 | <<locked>> | 80% | 41,930 psi | 67% | 2497 fps | 98.6% |
| Somchem S335 | <<locked>> | 80% | 37,579 psi | 60% | 2346 fps | 99.6% |
| Somchem S341 | <<locked>> | 80% | 36,651 psi | 59% | 2388 fps | 95.6% |
| Somchem S355 | <<locked>> | 84% | 33,156 psi | 53% | 2329 fps | 95.1% |
| Somchem S365 | <<locked>> | 92% | 30,676 psi | 49% | 2352 fps | 95.2% |
| Vihtavuori N130 | <<locked>> | 80% | 43,294 psi | 69% | 2418 fps | 100% |
| Vihtavuori N133 | <<locked>> | 80% | 38,218 psi | 61% | 2346 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 33,475 psi | 54% | 2323 fps | 99.9% |
| Vihtavuori N140 | <<locked>> | 80% | 34,447 psi | 55% | 2323 fps | 99% |
| Vihtavuori N150 | <<locked>> | 82% | 29,588 psi | 47% | 2231 fps | 95.3% |
| Vihtavuori N160 | <<locked>> | 96% | 41,075 psi | 66% | 2513 fps | 95.3% |
| Vihtavuori N530 | <<locked>> | 80% | 39,001 psi | 63% | 2418 fps | 97.8% |
| Vihtavuori N540 | <<locked>> | 80% | 33,025 psi | 53% | 2310 fps | 98.2% |
| Vihtavuori N550 | <<locked>> | 98% | 42,786 psi | 69% | 2566 fps | 95.7% |
| Winchester 6.5 StaBALL | <<locked>> | 90% | 34,563 psi | 55% | 2346 fps | 95.2% |
| Winchester 748 | <<locked>> | 80% | 37,782 psi | 61% | 2454 fps | 98.3% |
| Winchester StaBALL Match | <<locked>> | 80% | 34,809 psi | 56% | 2375 fps | 95.8% |
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 112 powders for .375 H&H Mag. loaded with the .375 | 250gr | Speer TBBC. ReloadSwiss RS 60 delivers the highest muzzle velocity at 2,835 fps; across all powders the maximum-charge window runs from 1,608 fps to 2,835 fps. Accurate 4350 gives the best case fill at 100 %, and 112 of the 112 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (430 MPa), the top charges use 50–90 %, leaving at least 10 % headroom. The 250.0 gr projectile in 0.375" calls for a 1:6.0 twist; slower twists will usually not stabilise this weight. Accurate 4350, Alliant Reloder-16, Alliant Reloder-17 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 Power Pro 2000-MR, Hodgdon CFE223, Ramshot Big Game rank at the top here: for .375 H&H Mag. with the .375 | 250gr | Speer TBBC they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Accurate 2700, Alliant Reloder-23, Bofors RP7 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.