Load Specifications
Load data in caliber .338 RCM with .338 | 225gr | NorthFork Bonded Core bullet and 97 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, ReloadSwiss RS 52 and Hodgdon CFE223.
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: 24"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 2015 | <<locked>> | 90% | 54,476 psi | 87% | 2454 fps | 100% |
| Accurate 2200 | <<locked>> | 82% | 54,969 psi | 88% | 2543 fps | 99.2% |
| Accurate 2230 | <<locked>> | 82% | 55,767 psi | 89% | 2552 fps | 99.4% |
| Accurate 2460 | <<locked>> | 86% | 52,910 psi | 85% | 2477 fps | 100% |
| Accurate 2495 | <<locked>> | 96% | 54,810 psi | 88% | 2510 fps | 100% |
| Accurate 2520 | <<locked>> | 90% | 54,447 psi | 87% | 2536 fps | 100% |
| Accurate 4064 | <<locked>> | 98% | 54,462 psi | 87% | 2549 fps | 100% |
| Accurate 4350ᴾ | <<locked>> | 100% | 43,250 psi | 69% | 2457 fps | 97.1% |
| Accurate LT-30 | <<locked>> | 84% | 54,853 psi | 88% | 2408 fps | 100% |
| Accurate LT-32 | <<locked>> | 84% | 55,259 psi | 89% | 2428 fps | 100% |
| ADI AR 2206H | <<locked>> | 92% | 53,563 psi | 86% | 2539 fps | 99.5% |
| ADI AR 2208 | <<locked>> | 98% | 54,331 psi | 87% | 2530 fps | 99.2% |
| ADI AR 2219 | <<locked>> | 84% | 55,158 psi | 88% | 2516 fps | 100% |
| ADI Benchmark 8208 | <<locked>> | 92% | 56,391 psi | 90% | 2543 fps | 100% |
| Alliant AR-Comp | <<locked>> | 92% | 55,709 psi | 89% | 2520 fps | 100% |
| Alliant Power Pro 1200-R | <<locked>> | 86% | 54,389 psi | 87% | 2592 fps | 99.8% |
| Alliant Power Pro 2000-MR | <<locked>> | 96% | 56,391 psi | 90% | 2684 fps | 99.4% |
| Alliant Reloder- TS 15.5 | <<locked>> | 98% | 53,359 psi | 86% | 2549 fps | 99.8% |
| Alliant Reloder-10x | <<locked>> | 86% | 54,534 psi | 87% | 2461 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 96% | 54,404 psi | 87% | 2569 fps | 99.3% |
| Alliant Reloder-16ᴾ | <<locked>> | 100% | 43,772 psi | 70% | 2461 fps | 97.2% |
| Alliant Reloder-17ᴾ | <<locked>> | 100% | 50,241 psi | 81% | 2602 fps | 99.6% |
| Baschieri & Pellagri 106 | <<locked>> | 84% | 53,795 psi | 86% | 2408 fps | 100% |
| Baschieri & Pellagri 107 | <<locked>> | 92% | 52,997 psi | 85% | 2549 fps | 98.8% |
| Bofors RP3 | <<locked>> | 98% | 53,432 psi | 86% | 2562 fps | 99.9% |
| Hodgdon Benchmark | <<locked>> | 90% | 55,187 psi | 88% | 2487 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 92% | 55,056 psi | 88% | 2575 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 88% | 52,924 psi | 85% | 2605 fps | 99.2% |
| Hodgdon H322 | <<locked>> | 86% | 53,548 psi | 86% | 2500 fps | 100% |
| Hodgdon H335 | <<locked>> | 86% | 54,636 psi | 88% | 2526 fps | 100% |
| Hodgdon H380 | <<locked>> | 98% | 55,259 psi | 89% | 2572 fps | 98.6% |
| Hodgdon H4895 | <<locked>> | 92% | 53,983 psi | 87% | 2549 fps | 99.8% |
| Hodgdon Hybrid 100Vᴾ | <<locked>> | 100% | 40,074 psi | 64% | 2362 fps | 97.8% |
| Hodgdon LEVERevolution | <<locked>> | 96% | 55,767 psi | 89% | 2618 fps | 100% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 34,389 psi | 55% | 1490 fps | 100% |
| Hodgdon VARGET | <<locked>> | 94% | 55,405 psi | 89% | 2549 fps | 99.8% |
| IMR 3031 | <<locked>> | 94% | 56,304 psi | 90% | 2575 fps | 100% |
| IMR 4064 | <<locked>> | 96% | 53,766 psi | 86% | 2513 fps | 99.3% |
| IMR 4166 Enduron | <<locked>> | 94% | 54,998 psi | 88% | 2500 fps | 96.4% |
| IMR 4198 | <<locked>> | 86% | 55,100 psi | 88% | 2425 fps | 100% |
| IMR 4451 Enduronᴾ | <<locked>> | 100% | 53,563 psi | 86% | 2510 fps | 96% |
| IMR 4831ᴾ | <<locked>> | 100% | 41,510 psi | 67% | 2408 fps | 96.7% |
| IMR 4895 | <<locked>> | 96% | 55,782 psi | 89% | 2598 fps | 99.7% |
| IMR 8208 XBR | <<locked>> | 92% | 56,391 psi | 90% | 2543 fps | 100% |
| Lovex D073.5 | <<locked>> | 86% | 52,837 psi | 85% | 2487 fps | 100% |
| Lovex D073.6 | <<locked>> | 94% | 55,695 psi | 89% | 2559 fps | 100% |
| Lovex S060 | <<locked>> | 92% | 54,012 psi | 87% | 2474 fps | 99.5% |
| Lovex S062 | <<locked>> | 96% | 53,069 psi | 85% | 2513 fps | 99.9% |
| Lovex S065ᴾ | <<locked>> | 100% | 49,081 psi | 79% | 2457 fps | 96.7% |
| Norma 200 | <<locked>> | 82% | 54,520 psi | 87% | 2434 fps | 100% |
| Norma 201 | <<locked>> | 94% | 55,419 psi | 89% | 2530 fps | 100% |
| Norma 202 | <<locked>> | 94% | 55,825 psi | 90% | 2536 fps | 100% |
| Norma 203B | <<locked>> | 96% | 53,490 psi | 86% | 2559 fps | 99.5% |
| Norma URPᴾ | <<locked>> | 100% | 43,714 psi | 70% | 2454 fps | 97% |
| Ramshot Big Game | <<locked>> | 96% | 53,679 psi | 86% | 2582 fps | 99.5% |
| Ramshot TAC | <<locked>> | 90% | 53,359 psi | 86% | 2510 fps | 97.7% |
| Ramshot Wild Boar | <<locked>> | 92% | 55,840 psi | 90% | 2575 fps | 99.6% |
| Ramshot X-Terminator | <<locked>> | 88% | 54,215 psi | 87% | 2500 fps | 99.4% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 34,780 psi | 56% | 1529 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 88% | 56,115 psi | 90% | 2530 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 98% | 56,072 psi | 90% | 2552 fps | 97.2% |
| ReloadSwiss RS 52 | <<locked>> | 94% | 53,751 psi | 86% | 2625 fps | 99.3% |
| ReloadSwiss RS 60ᴾ | <<locked>> | 100% | 53,664 psi | 86% | 2657 fps | 100% |
| ReloadSwiss RS 62ᴾ | <<locked>> | 100% | 43,279 psi | 69% | 2474 fps | 96.6% |
| Rottweil R 901 | <<locked>> | 90% | 53,476 psi | 86% | 2477 fps | 100% |
| Rottweil R 902 | <<locked>> | 96% | 55,898 psi | 90% | 2530 fps | 100% |
| Rottweil R 903ᴾ | <<locked>> | 100% | 53,272 psi | 85% | 2552 fps | 99.8% |
| Shooters World Long Rifleᴾ | <<locked>> | 100% | 49,081 psi | 79% | 2457 fps | 96.7% |
| Shooters World Match Rifle | <<locked>> | 94% | 55,695 psi | 89% | 2559 fps | 100% |
| Shooters World Precision | <<locked>> | 96% | 53,069 psi | 85% | 2513 fps | 99.9% |
| Shooters World Tactical Rifle | <<locked>> | 84% | 52,692 psi | 84% | 2461 fps | 99.8% |
| SNPE Vectan BA6 1/2 | <<locked>> | 82% | 55,405 psi | 89% | 2182 fps | 100% |
| SNPE Vectan SP 10 | <<locked>> | 84% | 55,332 psi | 89% | 2526 fps | 100% |
| SNPE Vectan SP 11ᴾ | <<locked>> | 100% | 55,027 psi | 88% | 2608 fps | 99.6% |
| SNPE Vectan SP 3 | <<locked>> | 86% | 55,521 psi | 89% | 2477 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 92% | 54,723 psi | 88% | 2533 fps | 98.3% |
| SNPE Vectan SP 9 | <<locked>> | 94% | 55,085 psi | 88% | 2556 fps | 99.6% |
| SNPE Vectan Tubal 3000 | <<locked>> | 92% | 54,578 psi | 88% | 2441 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 98% | 53,780 psi | 86% | 2434 fps | 100% |
| Somchem S321 | <<locked>> | 88% | 53,867 psi | 86% | 2530 fps | 100% |
| Somchem S335 | <<locked>> | 92% | 53,606 psi | 86% | 2444 fps | 100% |
| Somchem S341 | <<locked>> | 92% | 54,230 psi | 87% | 2530 fps | 99.5% |
| Somchem S355ᴾ | <<locked>> | 100% | 54,056 psi | 87% | 2552 fps | 99.7% |
| Somchem S365ᴾ | <<locked>> | 100% | 38,928 psi | 62% | 2408 fps | 98.9% |
| Vihtavuori N120 | <<locked>> | 82% | 56,318 psi | 90% | 2375 fps | 100% |
| Vihtavuori N130 | <<locked>> | 88% | 54,694 psi | 88% | 2418 fps | 100% |
| Vihtavuori N133 | <<locked>> | 92% | 54,404 psi | 87% | 2431 fps | 100% |
| Vihtavuori N135 | <<locked>> | 96% | 54,737 psi | 88% | 2500 fps | 100% |
| Vihtavuori N140 | <<locked>> | 96% | 56,391 psi | 90% | 2516 fps | 100% |
| Vihtavuori N150ᴾ | <<locked>> | 100% | 52,257 psi | 84% | 2493 fps | 100% |
| Vihtavuori N160ᴾ | <<locked>> | 100% | 46,180 psi | 74% | 2454 fps | 97.4% |
| Vihtavuori N530 | <<locked>> | 90% | 53,417 psi | 86% | 2500 fps | 99.9% |
| Vihtavuori N540 | <<locked>> | 96% | 54,418 psi | 87% | 2516 fps | 100% |
| Vihtavuori N550ᴾ | <<locked>> | 100% | 44,802 psi | 72% | 2457 fps | 97% |
| Winchester 6.5 StaBALLᴾ | <<locked>> | 100% | 47,311 psi | 76% | 2444 fps | 99.1% |
| Winchester 748 | <<locked>> | 92% | 55,840 psi | 90% | 2585 fps | 100% |
| Winchester StaBALL Match | <<locked>> | 94% | 54,926 psi | 88% | 2569 fps | 99.8% |
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% | 40,205 psi | 64% | 2257 fps | 100% |
| Accurate 2200 | <<locked>> | 80% | 51,503 psi | 83% | 2493 fps | 98.8% |
| Accurate 2230 | <<locked>> | 80% | 51,953 psi | 83% | 2500 fps | 99.1% |
| Accurate 2460 | <<locked>> | 80% | 43,439 psi | 70% | 2346 fps | 99.9% |
| Accurate 2495 | <<locked>> | 80% | 32,489 psi | 52% | 2175 fps | 100% |
| Accurate 2520 | <<locked>> | 80% | 38,711 psi | 62% | 2303 fps | 99.5% |
| Accurate 4064 | <<locked>> | 80% | 30,763 psi | 49% | 2159 fps | 98.8% |
| Accurate 4350 | <<locked>> | 96% | 37,608 psi | 60% | 2356 fps | 95.5% |
| Accurate LT-30 | <<locked>> | 80% | 48,660 psi | 78% | 2326 fps | 100% |
| Accurate LT-32 | <<locked>> | 80% | 49,052 psi | 79% | 2346 fps | 100% |
| ADI AR 2206H | <<locked>> | 80% | 36,811 psi | 59% | 2257 fps | 96.6% |
| ADI AR 2208 | <<locked>> | 84% | 35,491 psi | 57% | 2215 fps | 95.3% |
| ADI AR 2219 | <<locked>> | 80% | 48,124 psi | 77% | 2428 fps | 100% |
| ADI Benchmark 8208 | <<locked>> | 80% | 38,812 psi | 62% | 2274 fps | 98.3% |
| Alliant AR-Comp | <<locked>> | 80% | 37,594 psi | 60% | 2280 fps | 100% |
| Alliant Power Pro 1200-R | <<locked>> | 80% | 44,701 psi | 72% | 2444 fps | 98.9% |
| Alliant Power Pro 2000-MR | 49 gr | 84% | 37,811 psi | 61% | 2362 fps | 95.5% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 30,284 psi | 49% | 2142 fps | 95.4% |
| Alliant Reloder-10x | <<locked>> | 80% | 45,484 psi | 73% | 2343 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 82% | 35,012 psi | 56% | 2244 fps | 95.4% |
| Alliant Reloder-16 | <<locked>> | 96% | 38,914 psi | 62% | 2365 fps | 95.7% |
| Alliant Reloder-17 | <<locked>> | 88% | 33,953 psi | 54% | 2290 fps | 95.8% |
| Baschieri & Pellagri 106 | <<locked>> | 80% | 47,268 psi | 76% | 2326 fps | 100% |
| Baschieri & Pellagri 107 | <<locked>> | 82% | 38,029 psi | 61% | 2303 fps | 95.7% |
| Bofors RP3 | <<locked>> | 80% | 29,515 psi | 47% | 2139 fps | 95.2% |
| Hodgdon Benchmark | <<locked>> | 80% | 40,901 psi | 66% | 2270 fps | 99% |
| Hodgdon BL-C2 | <<locked>> | 80% | 36,782 psi | 59% | 2287 fps | 98.4% |
| Hodgdon CFE223 | 47.8 gr | 80% | 40,379 psi | 65% | 2398 fps | 97% |
| Hodgdon H322 | <<locked>> | 80% | 44,266 psi | 71% | 2369 fps | 100% |
| Hodgdon H335 | <<locked>> | 80% | 44,744 psi | 72% | 2388 fps | 100% |
| Hodgdon H380 | <<locked>> | 88% | 39,827 psi | 64% | 2329 fps | 95.4% |
| Hodgdon H4895 | <<locked>> | 80% | 37,043 psi | 59% | 2270 fps | 97.3% |
| Hodgdon Hybrid 100V | <<locked>> | 94% | 33,315 psi | 53% | 2224 fps | 95.6% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 33,156 psi | 53% | 2234 fps | 96.5% |
| Hodgdon TrailBoss | <<locked>> | 80% | 25,730 psi | 41% | 1332 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 35,824 psi | 57% | 2231 fps | 96.8% |
| IMR 3031 | <<locked>> | 80% | 35,752 psi | 57% | 2274 fps | 100% |
| IMR 4064 | <<locked>> | 82% | 35,070 psi | 56% | 2201 fps | 95.4% |
| IMR 4166 Enduron | <<locked>> | 90% | 48,646 psi | 78% | 2405 fps | 95% |
| IMR 4198 | <<locked>> | 80% | 46,398 psi | 74% | 2313 fps | 100% |
| IMR 4451 Enduron | <<locked>> | 98% | 50,386 psi | 81% | 2464 fps | 95.3% |
| IMR 4831 | <<locked>> | 96% | 36,521 psi | 59% | 2313 fps | 95.1% |
| IMR 4895 | <<locked>> | 80% | 33,518 psi | 54% | 2221 fps | 95.6% |
| IMR 8208 XBR | <<locked>> | 80% | 38,812 psi | 62% | 2274 fps | 98.3% |
| Lovex D073.5 | <<locked>> | 80% | 43,178 psi | 69% | 2349 fps | 99.6% |
| Lovex D073.6 | <<locked>> | 80% | 34,882 psi | 56% | 2241 fps | 98.9% |
| Lovex S060 | <<locked>> | 80% | 37,724 psi | 60% | 2211 fps | 96.8% |
| Lovex S062 | <<locked>> | 80% | 32,532 psi | 52% | 2162 fps | 96.7% |
| Lovex S065 | <<locked>> | 96% | 43,352 psi | 70% | 2365 fps | 95.3% |
| Norma 200 | <<locked>> | 80% | 51,169 psi | 82% | 2395 fps | 100% |
| Norma 201 | <<locked>> | 80% | 36,027 psi | 58% | 2221 fps | 97.7% |
| Norma 202 | <<locked>> | 80% | 36,100 psi | 58% | 2238 fps | 99.4% |
| Norma 203B | <<locked>> | 80% | 32,184 psi | 52% | 2185 fps | 95% |
| Norma URP | <<locked>> | 96% | 38,537 psi | 62% | 2359 fps | 95.5% |
| Ramshot Big Game | <<locked>> | 82% | 33,808 psi | 54% | 2238 fps | 95.2% |
| Ramshot TAC | <<locked>> | 84% | 44,048 psi | 71% | 2365 fps | 95.7% |
| Ramshot Wild Boar | <<locked>> | 80% | 37,594 psi | 60% | 2287 fps | 96.7% |
| Ramshot X-Terminator | <<locked>> | 80% | 42,163 psi | 68% | 2316 fps | 97.7% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 25,715 psi | 41% | 1362 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 80% | 43,656 psi | 70% | 2352 fps | 99.8% |
| ReloadSwiss RS 50 | <<locked>> | 92% | 46,267 psi | 74% | 2411 fps | 95.2% |
| ReloadSwiss RS 52 | 46.4 gr | 82% | 36,100 psi | 58% | 2326 fps | 95.7% |
| ReloadSwiss RS 60 | <<locked>> | 80% | 28,036 psi | 45% | 2146 fps | 95.6% |
| ReloadSwiss RS 62 | <<locked>> | 98% | 40,364 psi | 65% | 2421 fps | 95.8% |
| Rottweil R 901 | <<locked>> | 80% | 39,842 psi | 64% | 2270 fps | 99.7% |
| Rottweil R 902 | <<locked>> | 80% | 34,316 psi | 55% | 2178 fps | 97.2% |
| Rottweil R 903 | <<locked>> | 84% | 31,676 psi | 51% | 2182 fps | 95.7% |
| Shooters World Long Rifle | <<locked>> | 96% | 43,352 psi | 70% | 2365 fps | 95.3% |
| Shooters World Match Rifle | <<locked>> | 80% | 34,882 psi | 56% | 2241 fps | 98.9% |
| Shooters World Precision | <<locked>> | 80% | 32,532 psi | 52% | 2162 fps | 96.7% |
| Shooters World Tactical Rifle | <<locked>> | 80% | 46,122 psi | 74% | 2365 fps | 99.2% |
| SNPE Vectan BA6 1/2 | <<locked>> | 80% | 52,620 psi | 84% | 2152 fps | 100% |
| SNPE Vectan SP 10 | <<locked>> | 80% | 48,646 psi | 78% | 2438 fps | 100% |
| SNPE Vectan SP 11 | <<locked>> | 84% | 33,098 psi | 53% | 2228 fps | 95% |
| SNPE Vectan SP 3 | <<locked>> | 80% | 46,195 psi | 74% | 2356 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 82% | 39,146 psi | 63% | 2287 fps | 95% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 35,302 psi | 57% | 2228 fps | 96% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 37,840 psi | 61% | 2195 fps | 99.6% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 30,951 psi | 50% | 2077 fps | 99.1% |
| Somchem S321 | <<locked>> | 80% | 41,321 psi | 66% | 2343 fps | 99% |
| Somchem S335 | <<locked>> | 80% | 37,188 psi | 60% | 2198 fps | 99.8% |
| Somchem S341 | <<locked>> | 80% | 36,129 psi | 58% | 2241 fps | 96.2% |
| Somchem S355 | <<locked>> | 82% | 30,821 psi | 49% | 2146 fps | 95.1% |
| Somchem S365 | <<locked>> | 90% | 28,471 psi | 46% | 2165 fps | 95.1% |
| Vihtavuori N120 | <<locked>> | 80% | 52,852 psi | 85% | 2336 fps | 100% |
| Vihtavuori N130 | <<locked>> | 80% | 42,946 psi | 69% | 2260 fps | 100% |
| Vihtavuori N133 | <<locked>> | 80% | 37,913 psi | 61% | 2198 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 33,083 psi | 53% | 2175 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 34,055 psi | 55% | 2178 fps | 99.3% |
| Vihtavuori N150 | <<locked>> | 80% | 27,383 psi | 44% | 2047 fps | 95.2% |
| Vihtavuori N160 | <<locked>> | 94% | 38,130 psi | 61% | 2313 fps | 95.2% |
| Vihtavuori N530 | <<locked>> | 80% | 38,667 psi | 62% | 2267 fps | 98.3% |
| Vihtavuori N540 | <<locked>> | 80% | 32,808 psi | 53% | 2172 fps | 98.7% |
| Vihtavuori N550 | <<locked>> | 96% | 39,537 psi | 63% | 2362 fps | 95.5% |
| Winchester 6.5 StaBALL | <<locked>> | 88% | 32,024 psi | 51% | 2156 fps | 95% |
| Winchester 748 | <<locked>> | 80% | 37,318 psi | 60% | 2303 fps | 98.8% |
| Winchester StaBALL Match | <<locked>> | 80% | 34,432 psi | 55% | 2231 fps | 96.5% |
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 97 powders for .338 RCM loaded with the .338 | 225gr | NorthFork Bonded Core. Alliant Power Pro 2000-MR delivers the highest muzzle velocity at 2,684 fps; across all powders the maximum-charge window runs from 1,490 fps to 2,684 fps. Accurate 4350 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 (430 MPa), the top charges use 55–90 %, leaving at least 10 % headroom. The 225.0 gr projectile in 0.338" calls for a 1:15.0 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, ReloadSwiss RS 52, Hodgdon CFE223 rank at the top here: for .338 RCM with the .338 | 225gr | NorthFork Bonded Core 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.