Load Specifications
Load data in caliber .378 Weath. Mag. with .375 | 200gr | MAKER TREX bullet and 97 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ReloadSwiss RS 60, ReloadSwiss RS 70 and Hodgdon Superformance.
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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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 2015 | <<locked>> | 84% | 57,029 psi | 89% | 3179 fps | 100% |
| Accurate 2495 | <<locked>> | 88% | 55,753 psi | 87% | 3199 fps | 100% |
| Accurate 2520 | <<locked>> | 82% | 54,143 psi | 85% | 3222 fps | 100% |
| Accurate 2700 | <<locked>> | 88% | 55,216 psi | 87% | 3202 fps | 97% |
| Accurate 3100ᴾ | <<locked>> | 100% | 43,482 psi | 68% | 3074 fps | 96.3% |
| Accurate 4064 | <<locked>> | 90% | 56,115 psi | 88% | 3255 fps | 100% |
| Accurate 4350 | <<locked>> | 98% | 56,913 psi | 89% | 3353 fps | 99.7% |
| ADI AR 2206H | <<locked>> | 86% | 56,507 psi | 89% | 3297 fps | 100% |
| ADI AR 2208 | <<locked>> | 92% | 57,696 psi | 90% | 3297 fps | 99.9% |
| ADI Benchmark 8208 | <<locked>> | 84% | 55,288 psi | 87% | 3241 fps | 100% |
| Alliant AR-Comp | <<locked>> | 84% | 56,376 psi | 88% | 3212 fps | 100% |
| Alliant Power Pro 2000-MR | <<locked>> | 88% | 56,811 psi | 89% | 3432 fps | 99.9% |
| Alliant Reloder- TS 15.5 | <<locked>> | 90% | 54,244 psi | 85% | 3261 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 88% | 54,737 psi | 86% | 3284 fps | 99.8% |
| Alliant Reloder-16 | <<locked>> | 98% | 54,288 psi | 85% | 3356 fps | 99.8% |
| Alliant Reloder-17 | <<locked>> | 94% | 55,738 psi | 87% | 3396 fps | 100% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 41,408 psi | 65% | 3110 fps | 99.1% |
| Alliant Reloder-26ᴾ | <<locked>> | 100% | 47,007 psi | 74% | 3301 fps | 98.6% |
| Baschieri & Pellagri 107 | <<locked>> | 86% | 56,579 psi | 89% | 3310 fps | 99.7% |
| Bofors RP3 | <<locked>> | 90% | 54,897 psi | 86% | 3274 fps | 100% |
| Bofors RP7 | <<locked>> | 94% | 54,897 psi | 86% | 3241 fps | 97.2% |
| Hodgdon Benchmark | <<locked>> | 84% | 56,956 psi | 89% | 3222 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 84% | 54,984 psi | 86% | 3271 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 82% | 57,246 psi | 90% | 3386 fps | 99.9% |
| Hodgdon H380 | <<locked>> | 90% | 55,869 psi | 88% | 3291 fps | 99.4% |
| Hodgdon H414 | <<locked>> | 96% | 55,883 psi | 88% | 3346 fps | 98% |
| Hodgdon H4350 | <<locked>> | 94% | 56,304 psi | 88% | 3307 fps | 96.8% |
| Hodgdon H4895 | <<locked>> | 86% | 57,101 psi | 89% | 3310 fps | 100% |
| Hodgdon Hybrid 100Vᴾ | <<locked>> | 100% | 54,215 psi | 85% | 3274 fps | 100% |
| Hodgdon LEVERevolution | <<locked>> | 88% | 56,971 psi | 89% | 3340 fps | 100% |
| Hodgdon Superformance | <<locked>> | 96% | 56,942 psi | 89% | 3392 fps | 97.9% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,462 psi | 56% | 2051 fps | 100% |
| Hodgdon VARGET | <<locked>> | 86% | 54,708 psi | 86% | 3251 fps | 100% |
| IMR 3031 | <<locked>> | 86% | 57,217 psi | 90% | 3287 fps | 100% |
| IMR 4064 | <<locked>> | 90% | 57,101 psi | 89% | 3278 fps | 99.9% |
| IMR 4166 Enduron | <<locked>> | 88% | 56,971 psi | 89% | 3255 fps | 98% |
| IMR 4350 | <<locked>> | 98% | 55,637 psi | 87% | 3271 fps | 97.4% |
| IMR 4451 Enduron | <<locked>> | 94% | 56,913 psi | 89% | 3281 fps | 97.9% |
| IMR 4831ᴾ | <<locked>> | 100% | 57,334 psi | 90% | 3340 fps | 99.8% |
| IMR 4895 | <<locked>> | 88% | 56,173 psi | 88% | 3320 fps | 100% |
| IMR 8208 XBR | <<locked>> | 84% | 55,288 psi | 87% | 3241 fps | 100% |
| Lovex D073.6 | <<locked>> | 86% | 56,376 psi | 88% | 3264 fps | 100% |
| Lovex S060 | <<locked>> | 86% | 55,695 psi | 87% | 3215 fps | 100% |
| Lovex S062 | <<locked>> | 90% | 56,811 psi | 89% | 3268 fps | 100% |
| Lovex S065 | <<locked>> | 96% | 56,347 psi | 88% | 3271 fps | 98.9% |
| Lovex S070 | <<locked>> | 98% | 57,522 psi | 90% | 3310 fps | 98.4% |
| Norma 201 | <<locked>> | 86% | 54,839 psi | 86% | 3232 fps | 100% |
| Norma 202 | <<locked>> | 86% | 55,709 psi | 87% | 3235 fps | 100% |
| Norma 203B | <<locked>> | 90% | 57,624 psi | 90% | 3330 fps | 100% |
| Norma 204 | <<locked>> | 98% | 56,550 psi | 89% | 3327 fps | 96.3% |
| Norma URP | <<locked>> | 98% | 55,738 psi | 87% | 3337 fps | 99.6% |
| Ramshot Big Game | <<locked>> | 88% | 54,853 psi | 86% | 3297 fps | 99.9% |
| Ramshot Hunter | <<locked>> | 98% | 54,708 psi | 86% | 3330 fps | 98.6% |
| Ramshot TAC | <<locked>> | 84% | 55,709 psi | 87% | 3258 fps | 99% |
| Ramshot Wild Boar | <<locked>> | 84% | 55,521 psi | 87% | 3278 fps | 99.9% |
| Ramshot X-Terminator | <<locked>> | 82% | 56,188 psi | 88% | 3238 fps | 99.9% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,853 psi | 56% | 2096 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 90% | 56,072 psi | 88% | 3268 fps | 98.4% |
| ReloadSwiss RS 52 | <<locked>> | 86% | 55,361 psi | 87% | 3360 fps | 99.8% |
| ReloadSwiss RS 60 | <<locked>> | 92% | 55,317 psi | 87% | 3399 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 98% | 56,913 psi | 89% | 3376 fps | 99.6% |
| ReloadSwiss RS 70 | <<locked>> | 98% | 56,260 psi | 88% | 3409 fps | 99.5% |
| Rottweil R 901 | <<locked>> | 84% | 55,593 psi | 87% | 3212 fps | 100% |
| Rottweil R 902 | <<locked>> | 88% | 55,390 psi | 87% | 3228 fps | 100% |
| Rottweil R 903 | <<locked>> | 92% | 54,766 psi | 86% | 3264 fps | 100% |
| Rottweil R 907 | <<locked>> | 94% | 54,897 psi | 86% | 3241 fps | 97.2% |
| Shooters World Long Rifle | <<locked>> | 96% | 56,347 psi | 88% | 3271 fps | 98.9% |
| Shooters World Match Rifle | <<locked>> | 86% | 56,376 psi | 88% | 3264 fps | 100% |
| Shooters World Precision | <<locked>> | 90% | 56,811 psi | 89% | 3268 fps | 100% |
| Shooters World SW4350 | <<locked>> | 98% | 57,522 psi | 90% | 3310 fps | 98.4% |
| SNPE Vectan SP 11 | <<locked>> | 92% | 56,898 psi | 89% | 3337 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 84% | 54,143 psi | 85% | 3232 fps | 99.1% |
| SNPE Vectan SP 9 | <<locked>> | 86% | 54,926 psi | 86% | 3261 fps | 99.9% |
| SNPE Vectan Tubal 3000 | <<locked>> | 86% | 56,449 psi | 88% | 3166 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 92% | 57,043 psi | 89% | 3163 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 96% | 56,739 psi | 89% | 3219 fps | 98% |
| Somchem S321 | <<locked>> | 82% | 56,710 psi | 89% | 3274 fps | 100% |
| Somchem S335 | <<locked>> | 86% | 55,738 psi | 87% | 3159 fps | 100% |
| Somchem S341 | <<locked>> | 86% | 57,696 psi | 90% | 3284 fps | 100% |
| Somchem S355 | <<locked>> | 92% | 55,071 psi | 86% | 3268 fps | 100% |
| Somchem S365ᴾ | <<locked>> | 100% | 53,969 psi | 85% | 3337 fps | 100% |
| Somchem S385ᴾ | <<locked>> | 100% | 50,009 psi | 78% | 3199 fps | 96.2% |
| Vihtavuori N130 | <<locked>> | 82% | 55,898 psi | 88% | 3123 fps | 100% |
| Vihtavuori N133 | <<locked>> | 86% | 56,768 psi | 89% | 3150 fps | 100% |
| Vihtavuori N135 | <<locked>> | 88% | 55,405 psi | 87% | 3192 fps | 100% |
| Vihtavuori N140 | <<locked>> | 88% | 56,304 psi | 88% | 3209 fps | 100% |
| Vihtavuori N150 | <<locked>> | 94% | 56,695 psi | 89% | 3241 fps | 100% |
| Vihtavuori N160 | <<locked>> | 96% | 54,520 psi | 85% | 3274 fps | 99.5% |
| Vihtavuori N530 | <<locked>> | 84% | 55,782 psi | 87% | 3238 fps | 100% |
| Vihtavuori N540 | <<locked>> | 88% | 54,636 psi | 86% | 3202 fps | 100% |
| Vihtavuori N550 | <<locked>> | 98% | 57,421 psi | 90% | 3340 fps | 99.6% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 45,730 psi | 72% | 3196 fps | 98.9% |
| Winchester 6.5 StaBALL | <<locked>> | 96% | 55,056 psi | 86% | 3248 fps | 100% |
| Winchester 748 | <<locked>> | 84% | 56,086 psi | 88% | 3291 fps | 100% |
| Winchester 760 | <<locked>> | 96% | 56,231 psi | 88% | 3353 fps | 98.1% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 37,072 psi | 58% | 3110 fps | 99.1% |
| Winchester StaBALL Match | <<locked>> | 86% | 54,955 psi | 86% | 3268 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 2015 | <<locked>> | 80% | 50,198 psi | 79% | 3074 fps | 100% |
| Accurate 2495 | <<locked>> | 80% | 42,511 psi | 67% | 2979 fps | 100% |
| Accurate 2520 | <<locked>> | 80% | 50,415 psi | 79% | 3159 fps | 100% |
| Accurate 2700 | <<locked>> | 84% | 48,240 psi | 76% | 3074 fps | 95.4% |
| Accurate 3100 | <<locked>> | 98% | 40,524 psi | 64% | 3009 fps | 95.4% |
| Accurate 4064 | <<locked>> | 80% | 40,263 psi | 63% | 2972 fps | 100% |
| Accurate 4350 | <<locked>> | 84% | 34,301 psi | 54% | 2887 fps | 95% |
| ADI AR 2206H | <<locked>> | 80% | 46,456 psi | 73% | 3114 fps | 99.3% |
| ADI AR 2208 | <<locked>> | 80% | 39,378 psi | 62% | 2940 fps | 97.4% |
| ADI Benchmark 8208 | <<locked>> | 80% | 48,631 psi | 76% | 3123 fps | 99.9% |
| Alliant AR-Comp | <<locked>> | 80% | 49,168 psi | 77% | 3107 fps | 100% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 42,641 psi | 67% | 3150 fps | 98.1% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 39,131 psi | 61% | 2963 fps | 98.7% |
| Alliant Reloder-15 | <<locked>> | 80% | 42,047 psi | 66% | 3035 fps | 98.1% |
| Alliant Reloder-16 | <<locked>> | 84% | 34,476 psi | 54% | 2907 fps | 95.1% |
| Alliant Reloder-17 | <<locked>> | 80% | 33,910 psi | 53% | 2920 fps | 96.9% |
| Alliant Reloder-23 | <<locked>> | 92% | 31,937 psi | 50% | 2854 fps | 95.9% |
| Alliant Reloder-26 | <<locked>> | 94% | 37,536 psi | 59% | 3068 fps | 95.7% |
| Baschieri & Pellagri 107 | <<locked>> | 80% | 45,963 psi | 72% | 3114 fps | 98.5% |
| Bofors RP3 | <<locked>> | 80% | 38,841 psi | 61% | 2963 fps | 98.7% |
| Bofors RP7 | <<locked>> | 90% | 48,312 psi | 76% | 3120 fps | 95.7% |
| Hodgdon Benchmark | <<locked>> | 80% | 50,183 psi | 79% | 3110 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 80% | 47,819 psi | 75% | 3143 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 80% | 53,142 psi | 83% | 3317 fps | 99.7% |
| Hodgdon H380 | <<locked>> | 80% | 39,610 psi | 62% | 2969 fps | 96.3% |
| Hodgdon H414 | <<locked>> | 90% | 45,571 psi | 71% | 3150 fps | 95.8% |
| Hodgdon H4350 | <<locked>> | 90% | 49,443 psi | 77% | 3179 fps | 95.2% |
| Hodgdon H4895 | <<locked>> | 80% | 46,905 psi | 74% | 3127 fps | 99.6% |
| Hodgdon Hybrid 100V | <<locked>> | 84% | 31,604 psi | 50% | 2789 fps | 96% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 43,149 psi | 68% | 3091 fps | 99.4% |
| Hodgdon Superformance | 112.5 gr | 90% | 45,542 psi | 71% | 3169 fps | 95.2% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,324 psi | 41% | 1837 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 45,020 psi | 71% | 3071 fps | 99.3% |
| IMR 3031 | <<locked>> | 80% | 46,702 psi | 73% | 3120 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 41,307 psi | 65% | 2976 fps | 98% |
| IMR 4166 Enduron | <<locked>> | 80% | 43,976 psi | 69% | 3005 fps | 95.1% |
| IMR 4350 | <<locked>> | 92% | 45,876 psi | 72% | 3087 fps | 95.1% |
| IMR 4451 Enduron | <<locked>> | 86% | 44,237 psi | 69% | 3038 fps | 95.1% |
| IMR 4831 | <<locked>> | 86% | 35,650 psi | 56% | 2904 fps | 95.7% |
| IMR 4895 | <<locked>> | 80% | 43,120 psi | 68% | 3071 fps | 98.8% |
| IMR 8208 XBR | <<locked>> | 80% | 48,631 psi | 76% | 3123 fps | 99.9% |
| Lovex D073.6 | <<locked>> | 80% | 45,730 psi | 72% | 3084 fps | 100% |
| Lovex S060 | <<locked>> | 80% | 46,180 psi | 72% | 3041 fps | 99.2% |
| Lovex S062 | <<locked>> | 80% | 41,220 psi | 65% | 2979 fps | 99.3% |
| Lovex S065 | <<locked>> | 86% | 40,959 psi | 64% | 2969 fps | 95.8% |
| Lovex S070 | <<locked>> | 90% | 44,469 psi | 70% | 3064 fps | 95.6% |
| Norma 201 | <<locked>> | 80% | 45,266 psi | 71% | 3054 fps | 99.7% |
| Norma 202 | <<locked>> | 80% | 45,788 psi | 72% | 3068 fps | 100% |
| Norma 203B | <<locked>> | 80% | 41,437 psi | 65% | 3022 fps | 98.5% |
| Norma 204 | <<locked>> | 96% | 52,765 psi | 83% | 3261 fps | 95.5% |
| Norma URP | <<locked>> | 84% | 34,693 psi | 54% | 2894 fps | 95% |
| Ramshot Big Game | <<locked>> | 80% | 41,336 psi | 65% | 3035 fps | 98.3% |
| Ramshot Hunter | <<locked>> | 90% | 41,626 psi | 65% | 3068 fps | 95.6% |
| Ramshot TAC | <<locked>> | 80% | 48,602 psi | 76% | 3127 fps | 97.9% |
| Ramshot Wild Boar | <<locked>> | 80% | 48,399 psi | 76% | 3153 fps | 99.5% |
| Ramshot X-Terminator | <<locked>> | 80% | 52,591 psi | 82% | 3179 fps | 99.8% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,658 psi | 42% | 1880 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 82% | 42,975 psi | 67% | 3015 fps | 95.6% |
| ReloadSwiss RS 52 | <<locked>> | 80% | 44,686 psi | 70% | 3156 fps | 98.6% |
| ReloadSwiss RS 60 | 94.6 gr | 80% | 36,129 psi | 57% | 2999 fps | 99.5% |
| ReloadSwiss RS 62 | <<locked>> | 86% | 36,811 psi | 58% | 2972 fps | 95.6% |
| ReloadSwiss RS 70 | 105.7 gr | 88% | 39,450 psi | 62% | 3051 fps | 95.8% |
| Rottweil R 901 | <<locked>> | 80% | 49,124 psi | 77% | 3104 fps | 100% |
| Rottweil R 902 | <<locked>> | 80% | 43,091 psi | 68% | 3002 fps | 99.5% |
| Rottweil R 903 | <<locked>> | 80% | 36,419 psi | 57% | 2897 fps | 97.9% |
| Rottweil R 907 | <<locked>> | 90% | 48,312 psi | 76% | 3120 fps | 95.7% |
| Shooters World Long Rifle | <<locked>> | 86% | 40,959 psi | 64% | 2969 fps | 95.8% |
| Shooters World Match Rifle | <<locked>> | 80% | 45,730 psi | 72% | 3084 fps | 100% |
| Shooters World Precision | <<locked>> | 80% | 41,220 psi | 65% | 2979 fps | 99.3% |
| Shooters World SW4350 | <<locked>> | 90% | 44,469 psi | 70% | 3064 fps | 95.6% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 37,666 psi | 59% | 2956 fps | 97.4% |
| SNPE Vectan SP 7 | <<locked>> | 80% | 47,050 psi | 74% | 3100 fps | 98% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 44,991 psi | 71% | 3074 fps | 99% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 46,644 psi | 73% | 3005 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 38,899 psi | 61% | 2851 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 88% | 43,352 psi | 68% | 2969 fps | 95.1% |
| Somchem S321 | <<locked>> | 80% | 52,837 psi | 83% | 3209 fps | 100% |
| Somchem S335 | <<locked>> | 80% | 46,195 psi | 72% | 3002 fps | 100% |
| Somchem S341 | <<locked>> | 80% | 46,746 psi | 73% | 3094 fps | 99.3% |
| Somchem S355 | <<locked>> | 80% | 37,202 psi | 58% | 2907 fps | 97.9% |
| Somchem S365 | <<locked>> | 80% | 26,963 psi | 42% | 2700 fps | 95.2% |
| Somchem S385 | <<locked>> | 98% | 46,659 psi | 73% | 3133 fps | 95.3% |
| Vihtavuori N130 | <<locked>> | 80% | 52,605 psi | 82% | 3074 fps | 100% |
| Vihtavuori N133 | <<locked>> | 80% | 47,079 psi | 74% | 2999 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 42,757 psi | 67% | 2982 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 43,395 psi | 68% | 2992 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 35,476 psi | 56% | 2835 fps | 98.6% |
| Vihtavuori N160 | <<locked>> | 84% | 36,274 psi | 57% | 2900 fps | 95.6% |
| Vihtavuori N530 | <<locked>> | 80% | 48,805 psi | 76% | 3120 fps | 99.9% |
| Vihtavuori N540 | <<locked>> | 80% | 41,800 psi | 66% | 2976 fps | 100% |
| Vihtavuori N550 | <<locked>> | 84% | 35,781 psi | 56% | 2897 fps | 95.2% |
| Vihtavuori N555 | <<locked>> | 90% | 32,358 psi | 51% | 2877 fps | 95% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 31,430 psi | 49% | 2743 fps | 96.1% |
| Winchester 748 | <<locked>> | 80% | 48,820 psi | 77% | 3169 fps | 100% |
| Winchester 760 | <<locked>> | 90% | 45,672 psi | 72% | 3153 fps | 95.8% |
| Winchester StaBALL HD | <<locked>> | 94% | 30,182 psi | 47% | 2877 fps | 95.6% |
| Winchester StaBALL Match | <<locked>> | 80% | 44,672 psi | 70% | 3081 fps | 99.4% |
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 97 powders for .378 Weath. Mag. loaded with the .375 | 200gr | MAKER TREX. Alliant Power Pro 2000-MR delivers the highest muzzle velocity at 3,432 fps; across all powders the maximum-charge window runs from 2,051 fps to 3,432 fps. Accurate 3100 gives the best case fill at 100 %, and 97 of the 97 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 200.0 gr projectile in 0.375" calls for a 1:6.0 twist; slower twists will usually not stabilise this weight. Accurate 3100, Alliant Reloder-23, Alliant Reloder-26 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. ReloadSwiss RS 60, ReloadSwiss RS 70, Hodgdon Superformance rank at the top here: for .378 Weath. Mag. with the .375 | 200gr | MAKER TREX 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.