Load Specifications
Bullet:.338 | 275gr | Speer SSP
Bullet Manufacturer:Speer
Bullet Weight:275 gr
Bullet Diameter:0.338"
Bullet Length:<<locked>>
Caliber:.338 Weatherby RPM load data
Case Length (l3):2.55"
Cartridge Length (C.O.L.):<<locked>>
Case Capacity:81.6 Grains of Water
Primer Size:Large Rifle Magnum (LRM)
Barrel Length:24"
Max. allowed Pressure:65,000 psi
Recommended Twist Rate:1:16.0
Load data in caliber .338 Weatherby RPM with .338 | 275gr | Speer SSP bullet and 109 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are ReloadSwiss RS 70, Hodgdon Superformance and Alliant Reloder-17.
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>> | 82% | 56,043 psi | 86% | 2270 fps | 100% |
| Accurate 2495 | <<locked>> | 86% | 55,259 psi | 85% | 2300 fps | 100% |
| Accurate 2520 | <<locked>> | 82% | 56,695 psi | 87% | 2359 fps | 100% |
| Accurate 2700 | <<locked>> | 88% | 57,363 psi | 88% | 2365 fps | 99% |
| Accurate 3100ᴾ | <<locked>> | 100% | 45,513 psi | 70% | 2300 fps | 98.8% |
| Accurate 4064 | <<locked>> | 88% | 55,564 psi | 85% | 2346 fps | 100% |
| Accurate 4350 | <<locked>> | 96% | 55,230 psi | 85% | 2438 fps | 100% |
| ADI AR 2206H | <<locked>> | 86% | 58,726 psi | 90% | 2415 fps | 100% |
| ADI AR 2208 | <<locked>> | 90% | 56,289 psi | 87% | 2379 fps | 100% |
| ADI AR 2209ᴾ | <<locked>> | 100% | 53,156 psi | 82% | 2428 fps | 97.9% |
| ADI Benchmark 8208 | <<locked>> | 84% | 57,435 psi | 88% | 2365 fps | 100% |
| Alliant AR-Comp | <<locked>> | 82% | 55,564 psi | 85% | 2297 fps | 100% |
| Alliant Power Pro 2000-MR | <<locked>> | 86% | 54,839 psi | 84% | 2484 fps | 100% |
| Alliant Reloder- TS 15.5 | <<locked>> | 90% | 56,550 psi | 87% | 2395 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 88% | 57,130 psi | 88% | 2418 fps | 100% |
| Alliant Reloder-16 | <<locked>> | 98% | 56,028 psi | 86% | 2480 fps | 100% |
| Alliant Reloder-17 | <<locked>> | 94% | 57,392 psi | 88% | 2510 fps | 100% |
| Alliant Reloder-19ᴾ | <<locked>> | 100% | 51,982 psi | 80% | 2415 fps | 97.9% |
| Alliant Reloder-22ᴾ | <<locked>> | 100% | 45,672 psi | 70% | 2369 fps | 96.8% |
| Alliant Reloder-23ᴾ | <<locked>> | 100% | 43,004 psi | 66% | 2320 fps | 100% |
| Alliant Reloder-25ᴾ | <<locked>> | 100% | 37,971 psi | 58% | 2251 fps | 97.9% |
| Alliant Reloder-26ᴾ | <<locked>> | 100% | 48,327 psi | 74% | 2474 fps | 99.9% |
| Baschieri & Pellagri 107 | <<locked>> | 86% | 58,552 psi | 90% | 2434 fps | 100% |
| Bofors RP3 | <<locked>> | 90% | 57,159 psi | 88% | 2408 fps | 100% |
| Bofors RP5ᴾ | <<locked>> | 100% | 45,672 psi | 70% | 2369 fps | 96.8% |
| Bofors RP7 | <<locked>> | 94% | 56,811 psi | 87% | 2395 fps | 99.1% |
| Hodgdon Benchmark | <<locked>> | 82% | 55,622 psi | 86% | 2306 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 84% | 57,203 psi | 88% | 2398 fps | 100% |
| Hodgdon H380 | <<locked>> | 90% | 57,856 psi | 89% | 2425 fps | 100% |
| Hodgdon H414 | <<locked>> | 96% | 57,914 psi | 89% | 2484 fps | 99.6% |
| Hodgdon H4350 | <<locked>> | 94% | 58,262 psi | 90% | 2448 fps | 98.9% |
| Hodgdon H4895 | <<locked>> | 84% | 55,709 psi | 86% | 2379 fps | 100% |
| Hodgdon Hybrid 100Vᴾ | <<locked>> | 100% | 56,304 psi | 87% | 2415 fps | 100% |
| Hodgdon LEVERevolution | <<locked>> | 86% | 55,405 psi | 85% | 2415 fps | 100% |
| Hodgdon Superformance | <<locked>> | 96% | 58,334 psi | 90% | 2526 fps | 99.5% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 35,955 psi | 55% | 1417 fps | 100% |
| Hodgdon VARGET | <<locked>> | 86% | 56,826 psi | 87% | 2382 fps | 100% |
| IMR 3031 | <<locked>> | 84% | 56,362 psi | 87% | 2359 fps | 100% |
| IMR 4064 | <<locked>> | 88% | 55,622 psi | 86% | 2359 fps | 100% |
| IMR 4166 Enduron | <<locked>> | 86% | 55,245 psi | 85% | 2349 fps | 99.3% |
| IMR 4350 | <<locked>> | 98% | 57,232 psi | 88% | 2421 fps | 99.2% |
| IMR 4451 Enduron | <<locked>> | 94% | 58,624 psi | 90% | 2418 fps | 99.5% |
| IMR 4831 | <<locked>> | 98% | 55,767 psi | 86% | 2431 fps | 100% |
| IMR 4895 | <<locked>> | 88% | 58,581 psi | 90% | 2441 fps | 100% |
| IMR 4955 Enduronᴾ | <<locked>> | 100% | 52,924 psi | 81% | 2369 fps | 96.2% |
| IMR 8208 XBR | <<locked>> | 84% | 57,435 psi | 88% | 2365 fps | 100% |
| Lovex D073.6 | <<locked>> | 86% | 58,798 psi | 90% | 2388 fps | 100% |
| Lovex S060 | <<locked>> | 86% | 57,754 psi | 89% | 2346 fps | 100% |
| Lovex S062 | <<locked>> | 88% | 55,593 psi | 86% | 2352 fps | 100% |
| Lovex S065 | <<locked>> | 96% | 58,320 psi | 90% | 2415 fps | 100% |
| Lovex S070 | <<locked>> | 96% | 55,782 psi | 86% | 2405 fps | 99.5% |
| Lovex S071ᴾ | <<locked>> | 100% | 37,942 psi | 58% | 2178 fps | 97.3% |
| Norma 201 | <<locked>> | 86% | 57,334 psi | 88% | 2362 fps | 100% |
| Norma 202 | <<locked>> | 86% | 57,972 psi | 89% | 2359 fps | 100% |
| Norma 203B | <<locked>> | 88% | 56,333 psi | 87% | 2405 fps | 100% |
| Norma 204 | <<locked>> | 98% | 58,175 psi | 89% | 2474 fps | 98.6% |
| Norma MRPᴾ | <<locked>> | 100% | 48,225 psi | 74% | 2438 fps | 98.6% |
| Norma URP | <<locked>> | 98% | 57,725 psi | 89% | 2470 fps | 100% |
| Ramshot Big Game | <<locked>> | 88% | 56,884 psi | 88% | 2431 fps | 100% |
| Ramshot Hunter | <<locked>> | 98% | 56,405 psi | 87% | 2474 fps | 99.8% |
| Ramshot TAC | <<locked>> | 84% | 57,696 psi | 89% | 2398 fps | 100% |
| Ramshot Wild Boar | <<locked>> | 84% | 57,653 psi | 89% | 2408 fps | 100% |
| Ramshot X-Terminator | <<locked>> | 82% | 58,276 psi | 90% | 2372 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 36,506 psi | 56% | 1453 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 90% | 58,102 psi | 89% | 2415 fps | 99.8% |
| ReloadSwiss RS 52 | <<locked>> | 86% | 58,001 psi | 89% | 2477 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 92% | 57,174 psi | 88% | 2503 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 98% | 58,610 psi | 90% | 2503 fps | 100% |
| ReloadSwiss RS 70 | <<locked>> | 98% | 57,740 psi | 89% | 2533 fps | 100% |
| Rottweil R 901 | <<locked>> | 84% | 58,421 psi | 90% | 2339 fps | 100% |
| Rottweil R 902 | <<locked>> | 88% | 58,030 psi | 89% | 2362 fps | 100% |
| Rottweil R 903 | <<locked>> | 92% | 57,058 psi | 88% | 2402 fps | 100% |
| Rottweil R 904ᴾ | <<locked>> | 100% | 54,853 psi | 84% | 2402 fps | 97.2% |
| Rottweil R 905ᴾ | <<locked>> | 100% | 50,894 psi | 78% | 2402 fps | 97.9% |
| Rottweil R 907 | <<locked>> | 94% | 56,811 psi | 87% | 2395 fps | 99.1% |
| Shooters World Long Rifle | <<locked>> | 96% | 58,320 psi | 90% | 2415 fps | 100% |
| Shooters World Match Rifle | <<locked>> | 86% | 58,798 psi | 90% | 2388 fps | 100% |
| Shooters World Precision | <<locked>> | 88% | 55,593 psi | 86% | 2352 fps | 100% |
| Shooters World SW4350 | <<locked>> | 96% | 55,782 psi | 86% | 2405 fps | 99.5% |
| SNPE Vectan SP 11 | <<locked>> | 90% | 55,303 psi | 85% | 2418 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 84% | 56,333 psi | 87% | 2379 fps | 100% |
| SNPE Vectan SP 9 | <<locked>> | 86% | 57,145 psi | 88% | 2395 fps | 100% |
| SNPE Vectan Tubal 3000 | <<locked>> | 84% | 55,347 psi | 85% | 2264 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 90% | 55,506 psi | 85% | 2264 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 96% | 58,407 psi | 90% | 2375 fps | 99.5% |
| SNPE Vectan Tubal 8000ᴾ | <<locked>> | 100% | 50,415 psi | 78% | 2395 fps | 97.8% |
| Somchem S335 | <<locked>> | 86% | 58,001 psi | 89% | 2300 fps | 100% |
| Somchem S341 | <<locked>> | 84% | 56,028 psi | 86% | 2369 fps | 100% |
| Somchem S355 | <<locked>> | 92% | 57,188 psi | 88% | 2398 fps | 100% |
| Somchem S361ᴾ | <<locked>> | 100% | 56,666 psi | 87% | 2398 fps | 96.6% |
| Somchem S365ᴾ | <<locked>> | 100% | 56,144 psi | 86% | 2467 fps | 100% |
| Somchem S385ᴾ | <<locked>> | 100% | 51,706 psi | 80% | 2385 fps | 98.6% |
| Vihtavuori N130 | <<locked>> | 82% | 58,392 psi | 90% | 2260 fps | 100% |
| Vihtavuori N133 | <<locked>> | 84% | 55,753 psi | 86% | 2247 fps | 100% |
| Vihtavuori N135 | <<locked>> | 88% | 57,899 psi | 89% | 2323 fps | 100% |
| Vihtavuori N140 | <<locked>> | 88% | 58,668 psi | 90% | 2343 fps | 100% |
| Vihtavuori N150 | <<locked>> | 94% | 58,740 psi | 90% | 2379 fps | 100% |
| Vihtavuori N160 | <<locked>> | 96% | 56,565 psi | 87% | 2418 fps | 100% |
| Vihtavuori N165ᴾ | <<locked>> | 100% | 44,512 psi | 68% | 2270 fps | 96.8% |
| Vihtavuori N530 | <<locked>> | 84% | 58,059 psi | 89% | 2365 fps | 100% |
| Vihtavuori N540 | <<locked>> | 88% | 56,666 psi | 87% | 2346 fps | 100% |
| Vihtavuori N550 | <<locked>> | 96% | 55,448 psi | 85% | 2428 fps | 100% |
| Vihtavuori N555ᴾ | <<locked>> | 100% | 47,935 psi | 74% | 2385 fps | 100% |
| Winchester 6.5 StaBALL | <<locked>> | 96% | 56,347 psi | 87% | 2398 fps | 100% |
| Winchester 748 | <<locked>> | 84% | 58,378 psi | 90% | 2411 fps | 100% |
| Winchester 760 | <<locked>> | 96% | 57,914 psi | 89% | 2484 fps | 99.6% |
| Winchester StaBALL HDᴾ | <<locked>> | 100% | 38,653 psi | 59% | 2359 fps | 100% |
| Winchester StaBALL Match | <<locked>> | 86% | 56,956 psi | 88% | 2402 fps | 100% |
| Winchester Supreme 780ᴾ | <<locked>> | 100% | 48,530 psi | 75% | 2333 fps | 97% |
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% | 52,765 psi | 81% | 2231 fps | 100% |
| Accurate 2495 | <<locked>> | 80% | 45,672 psi | 70% | 2185 fps | 100% |
| Accurate 2520 | <<locked>> | 80% | 53,127 psi | 82% | 2316 fps | 100% |
| Accurate 2700 | <<locked>> | 80% | 44,208 psi | 68% | 2182 fps | 96.9% |
| Accurate 3100 | <<locked>> | 90% | 32,547 psi | 50% | 2073 fps | 95.6% |
| Accurate 4064 | <<locked>> | 80% | 43,221 psi | 66% | 2188 fps | 100% |
| Accurate 4350 | <<locked>> | 80% | 32,126 psi | 49% | 2070 fps | 97.3% |
| ADI AR 2206H | <<locked>> | 80% | 48,733 psi | 75% | 2287 fps | 100% |
| ADI AR 2208 | <<locked>> | 80% | 41,423 psi | 64% | 2165 fps | 99.5% |
| ADI AR 2209 | <<locked>> | 92% | 41,292 psi | 64% | 2238 fps | 95.1% |
| ADI Benchmark 8208 | <<locked>> | 80% | 50,807 psi | 78% | 2283 fps | 100% |
| Alliant AR-Comp | <<locked>> | 80% | 52,112 psi | 80% | 2257 fps | 100% |
| Alliant Power Pro 2000-MR | <<locked>> | 80% | 44,715 psi | 69% | 2336 fps | 99.9% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 41,495 psi | 64% | 2188 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 80% | 44,353 psi | 68% | 2241 fps | 99.8% |
| Alliant Reloder-16 | <<locked>> | 80% | 32,227 psi | 50% | 2083 fps | 97.5% |
| Alliant Reloder-17 | 52.9 gr | 80% | 35,926 psi | 55% | 2185 fps | 99.6% |
| Alliant Reloder-19 | <<locked>> | 92% | 40,640 psi | 63% | 2234 fps | 95.2% |
| Alliant Reloder-22 | <<locked>> | 96% | 40,306 psi | 62% | 2274 fps | 95.3% |
| Alliant Reloder-23 | <<locked>> | 82% | 24,932 psi | 38% | 1926 fps | 95.7% |
| Alliant Reloder-25 | <<locked>> | 94% | 31,604 psi | 49% | 2106 fps | 95.3% |
| Alliant Reloder-26 | <<locked>> | 86% | 29,921 psi | 46% | 2113 fps | 95.7% |
| Baschieri & Pellagri 107 | <<locked>> | 80% | 48,211 psi | 74% | 2303 fps | 99.9% |
| Bofors RP3 | <<locked>> | 80% | 41,437 psi | 64% | 2198 fps | 100% |
| Bofors RP5 | <<locked>> | 96% | 40,306 psi | 62% | 2274 fps | 95.3% |
| Bofors RP7 | <<locked>> | 80% | 37,043 psi | 57% | 2090 fps | 95.2% |
| Hodgdon Benchmark | <<locked>> | 80% | 52,243 psi | 80% | 2267 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 80% | 50,053 psi | 77% | 2313 fps | 100% |
| Hodgdon H380 | <<locked>> | 80% | 41,945 psi | 65% | 2201 fps | 99% |
| Hodgdon H414 | <<locked>> | 80% | 34,229 psi | 53% | 2110 fps | 95% |
| Hodgdon H4350 | <<locked>> | 82% | 39,842 psi | 61% | 2172 fps | 95.3% |
| Hodgdon H4895 | <<locked>> | 80% | 49,211 psi | 76% | 2297 fps | 100% |
| Hodgdon Hybrid 100V | <<locked>> | 80% | 29,747 psi | 46% | 1998 fps | 98.1% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 45,556 psi | 70% | 2283 fps | 100% |
| Hodgdon Superformance | 58.7 gr | 84% | 38,261 psi | 59% | 2215 fps | 95.8% |
| Hodgdon TrailBoss | <<locked>> | 80% | 26,905 psi | 41% | 1266 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 47,297 psi | 73% | 2257 fps | 100% |
| IMR 3031 | <<locked>> | 80% | 49,443 psi | 76% | 2277 fps | 100% |
| IMR 4064 | <<locked>> | 80% | 43,540 psi | 67% | 2192 fps | 99.8% |
| IMR 4166 Enduron | <<locked>> | 80% | 45,905 psi | 71% | 2215 fps | 98% |
| IMR 4350 | <<locked>> | 84% | 37,159 psi | 57% | 2116 fps | 95.3% |
| IMR 4451 Enduron | <<locked>> | 80% | 38,406 psi | 59% | 2113 fps | 96.1% |
| IMR 4831 | <<locked>> | 80% | 31,227 psi | 48% | 2037 fps | 97% |
| IMR 4895 | <<locked>> | 80% | 45,440 psi | 70% | 2267 fps | 100% |
| IMR 4955 Enduron | <<locked>> | 98% | 49,661 psi | 76% | 2323 fps | 95.5% |
| IMR 8208 XBR | <<locked>> | 80% | 50,807 psi | 78% | 2283 fps | 100% |
| Lovex D073.6 | <<locked>> | 80% | 48,269 psi | 74% | 2264 fps | 100% |
| Lovex S060 | <<locked>> | 80% | 48,254 psi | 74% | 2224 fps | 100% |
| Lovex S062 | <<locked>> | 80% | 43,569 psi | 67% | 2192 fps | 100% |
| Lovex S065 | <<locked>> | 80% | 35,911 psi | 55% | 2073 fps | 97% |
| Lovex S070 | <<locked>> | 80% | 34,200 psi | 53% | 2057 fps | 95.2% |
| Lovex S071 | <<locked>> | 94% | 31,372 psi | 48% | 2051 fps | 95.1% |
| Norma 201 | <<locked>> | 80% | 47,747 psi | 73% | 2241 fps | 100% |
| Norma 202 | <<locked>> | 80% | 48,269 psi | 74% | 2241 fps | 100% |
| Norma 203B | <<locked>> | 80% | 43,758 psi | 67% | 2231 fps | 99.9% |
| Norma 204 | <<locked>> | 88% | 41,785 psi | 64% | 2234 fps | 95.3% |
| Norma MRP | <<locked>> | 92% | 36,941 psi | 57% | 2238 fps | 95.7% |
| Norma URP | <<locked>> | 80% | 32,445 psi | 50% | 2073 fps | 97.2% |
| Ramshot Big Game | <<locked>> | 80% | 43,497 psi | 67% | 2251 fps | 99.9% |
| Ramshot Hunter | <<locked>> | 82% | 33,649 psi | 52% | 2106 fps | 95.7% |
| Ramshot TAC | <<locked>> | 80% | 50,749 psi | 78% | 2310 fps | 99.6% |
| Ramshot Wild Boar | <<locked>> | 80% | 50,546 psi | 78% | 2320 fps | 100% |
| Ramshot X-Terminator | <<locked>> | 80% | 54,534 psi | 84% | 2329 fps | 100% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 27,282 psi | 42% | 1296 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 80% | 42,090 psi | 65% | 2188 fps | 97.8% |
| ReloadSwiss RS 52 | <<locked>> | 80% | 47,384 psi | 73% | 2336 fps | 100% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 38,247 psi | 59% | 2234 fps | 100% |
| ReloadSwiss RS 62 | <<locked>> | 80% | 31,734 psi | 49% | 2083 fps | 96.8% |
| ReloadSwiss RS 70 | 53.7 gr | 80% | 31,560 psi | 49% | 2087 fps | 95.9% |
| Rottweil R 901 | <<locked>> | 80% | 51,938 psi | 80% | 2260 fps | 100% |
| Rottweil R 902 | <<locked>> | 80% | 45,527 psi | 70% | 2205 fps | 100% |
| Rottweil R 903 | <<locked>> | 80% | 39,059 psi | 60% | 2152 fps | 99.8% |
| Rottweil R 904 | <<locked>> | 94% | 45,498 psi | 70% | 2267 fps | 95.1% |
| Rottweil R 905 | <<locked>> | 92% | 39,247 psi | 60% | 2215 fps | 95% |
| Rottweil R 907 | <<locked>> | 80% | 37,043 psi | 57% | 2090 fps | 95.2% |
| Shooters World Long Rifle | <<locked>> | 80% | 35,911 psi | 55% | 2073 fps | 97% |
| Shooters World Match Rifle | <<locked>> | 80% | 48,269 psi | 74% | 2264 fps | 100% |
| Shooters World Precision | <<locked>> | 80% | 43,569 psi | 67% | 2192 fps | 100% |
| Shooters World SW4350 | <<locked>> | 80% | 34,200 psi | 53% | 2057 fps | 95.2% |
| SNPE Vectan SP 11 | <<locked>> | 80% | 39,972 psi | 61% | 2198 fps | 99.7% |
| SNPE Vectan SP 7 | <<locked>> | 80% | 49,269 psi | 76% | 2290 fps | 99.7% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 47,282 psi | 73% | 2267 fps | 100% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 48,965 psi | 75% | 2188 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 41,075 psi | 63% | 2083 fps | 100% |
| SNPE Vectan Tubal 7000 | <<locked>> | 80% | 35,027 psi | 54% | 2028 fps | 95.3% |
| SNPE Vectan Tubal 8000 | <<locked>> | 94% | 41,568 psi | 64% | 2257 fps | 95.7% |
| Somchem S335 | <<locked>> | 80% | 48,501 psi | 75% | 2188 fps | 100% |
| Somchem S341 | <<locked>> | 80% | 49,052 psi | 75% | 2283 fps | 100% |
| Somchem S355 | <<locked>> | 80% | 39,581 psi | 61% | 2152 fps | 99.8% |
| Somchem S361 | <<locked>> | 96% | 49,603 psi | 76% | 2303 fps | 95.1% |
| Somchem S365 | <<locked>> | 80% | 29,008 psi | 45% | 2034 fps | 99.1% |
| Somchem S385 | <<locked>> | 90% | 37,391 psi | 58% | 2159 fps | 95.4% |
| Vihtavuori N130 | <<locked>> | 80% | 55,042 psi | 85% | 2224 fps | 100% |
| Vihtavuori N133 | <<locked>> | 80% | 49,443 psi | 76% | 2175 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 45,469 psi | 70% | 2175 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 45,788 psi | 70% | 2188 fps | 100% |
| Vihtavuori N150 | <<locked>> | 80% | 37,753 psi | 58% | 2096 fps | 100% |
| Vihtavuori N160 | <<locked>> | 80% | 33,707 psi | 52% | 2070 fps | 97.5% |
| Vihtavuori N165 | <<locked>> | 96% | 39,233 psi | 60% | 2182 fps | 95.4% |
| Vihtavuori N530 | <<locked>> | 80% | 51,169 psi | 79% | 2283 fps | 100% |
| Vihtavuori N540 | <<locked>> | 80% | 43,976 psi | 68% | 2185 fps | 100% |
| Vihtavuori N550 | <<locked>> | 80% | 33,199 psi | 51% | 2073 fps | 97.2% |
| Vihtavuori N555 | <<locked>> | 82% | 26,803 psi | 41% | 1988 fps | 95.8% |
| Winchester 6.5 StaBALL | <<locked>> | 80% | 33,228 psi | 51% | 2051 fps | 99.1% |
| Winchester 748 | <<locked>> | 80% | 51,285 psi | 79% | 2326 fps | 100% |
| Winchester 760 | <<locked>> | 80% | 34,403 psi | 53% | 2113 fps | 95.1% |
| Winchester StaBALL HD | <<locked>> | 86% | 24,816 psi | 38% | 1995 fps | 96.2% |
| Winchester StaBALL Match | <<locked>> | 80% | 46,963 psi | 72% | 2274 fps | 100% |
| Winchester Supreme 780 | <<locked>> | 96% | 42,351 psi | 65% | 2238 fps | 95.5% |
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 109 powders for .338 Weatherby RPM loaded with the .338 | 275gr | Speer SSP. ReloadSwiss RS 70 delivers the highest muzzle velocity at 2,533 fps; across all powders the maximum-charge window runs from 1,417 fps to 2,533 fps. Accurate 3100 gives the best case fill at 100 %, and 109 of the 109 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (448 MPa), the top charges use 55–90 %, leaving at least 10 % headroom. The 275.0 gr projectile in 0.338" calls for a 1:16.0 twist; slower twists will usually not stabilise this weight. Accurate 3100, ADI AR 2209, Alliant Reloder-19 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 70, Hodgdon Superformance, Alliant Reloder-17 rank at the top here: for .338 Weatherby RPM with the .338 | 275gr | Speer SSP 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.