Load Specifications
Load data in caliber .300 RCM with .308 | 150gr | Lapua Mega bullet and 94 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 ReloadSwiss RS 60.
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>> | 88% | 55,114 psi | 86% | 2874 fps | 100% |
| Accurate 2460 | <<locked>> | 86% | 57,290 psi | 90% | 2949 fps | 100% |
| Accurate 2495 | <<locked>> | 94% | 56,463 psi | 88% | 2940 fps | 100% |
| Accurate 2520 | <<locked>> | 88% | 55,463 psi | 87% | 2959 fps | 100% |
| Accurate 4064 | <<locked>> | 96% | 55,999 psi | 88% | 2979 fps | 100% |
| Accurate 4350ᴾ | <<locked>> | 100% | 48,167 psi | 75% | 2927 fps | 97.6% |
| Accurate LT-30 | <<locked>> | 82% | 54,404 psi | 85% | 2815 fps | 100% |
| Accurate LT-32 | <<locked>> | 82% | 54,795 psi | 86% | 2841 fps | 100% |
| ADI AR 2206H | <<locked>> | 92% | 57,638 psi | 90% | 3015 fps | 99.6% |
| ADI AR 2208 | <<locked>> | 96% | 55,129 psi | 86% | 2956 fps | 99.1% |
| ADI AR 2219 | <<locked>> | 82% | 55,448 psi | 87% | 2940 fps | 100% |
| ADI Benchmark 8208 | <<locked>> | 90% | 56,782 psi | 89% | 2969 fps | 99.9% |
| Alliant AR-Comp | <<locked>> | 90% | 56,942 psi | 89% | 2949 fps | 100% |
| Alliant Power Pro 1200-R | <<locked>> | 84% | 54,926 psi | 86% | 3025 fps | 99.7% |
| Alliant Power Pro 2000-MR | <<locked>> | 94% | 57,450 psi | 90% | 3133 fps | 99.4% |
| Alliant Reloder- TS 15.5 | <<locked>> | 96% | 54,404 psi | 85% | 2979 fps | 99.8% |
| Alliant Reloder-10x | <<locked>> | 84% | 54,853 psi | 86% | 2881 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 94% | 55,477 psi | 87% | 3002 fps | 99.2% |
| Alliant Reloder-16ᴾ | <<locked>> | 100% | 47,674 psi | 75% | 2933 fps | 97.7% |
| Alliant Reloder-17ᴾ | <<locked>> | 100% | 55,332 psi | 87% | 3097 fps | 99.8% |
| Baschieri & Pellagri 106 | <<locked>> | 84% | 57,450 psi | 90% | 2861 fps | 100% |
| Baschieri & Pellagri 107 | <<locked>> | 92% | 57,653 psi | 90% | 3028 fps | 99.1% |
| Bofors RP3 | <<locked>> | 96% | 55,143 psi | 86% | 2995 fps | 99.9% |
| Hodgdon Benchmark | <<locked>> | 88% | 55,608 psi | 87% | 2907 fps | 100% |
| Hodgdon BL-C2 | <<locked>> | 90% | 56,028 psi | 88% | 3002 fps | 100% |
| Hodgdon CFE223 | <<locked>> | 86% | 53,911 psi | 84% | 3038 fps | 99.1% |
| Hodgdon H322 | <<locked>> | 86% | 57,624 psi | 90% | 2969 fps | 100% |
| Hodgdon H335 | <<locked>> | 84% | 55,245 psi | 87% | 2949 fps | 100% |
| Hodgdon H380 | <<locked>> | 96% | 56,623 psi | 89% | 3005 fps | 98.5% |
| Hodgdon H4895 | <<locked>> | 90% | 54,578 psi | 86% | 2972 fps | 99.7% |
| Hodgdon Hybrid 100Vᴾ | <<locked>> | 100% | 43,729 psi | 69% | 2812 fps | 98.3% |
| Hodgdon LEVERevolution | <<locked>> | 94% | 57,058 psi | 89% | 3054 fps | 99.9% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 34,853 psi | 55% | 1798 fps | 100% |
| Hodgdon VARGET | <<locked>> | 92% | 55,999 psi | 88% | 2976 fps | 99.7% |
| IMR 3031 | <<locked>> | 92% | 57,696 psi | 90% | 3015 fps | 100% |
| IMR 4064 | <<locked>> | 94% | 54,766 psi | 86% | 2943 fps | 99.2% |
| IMR 4166 Enduron | <<locked>> | 92% | 55,230 psi | 87% | 2913 fps | 96.1% |
| IMR 4198 | <<locked>> | 84% | 55,129 psi | 86% | 2841 fps | 100% |
| IMR 4451 Enduron | <<locked>> | 98% | 54,288 psi | 85% | 2930 fps | 95.8% |
| IMR 4831ᴾ | <<locked>> | 100% | 45,934 psi | 72% | 2867 fps | 97.2% |
| IMR 4895 | <<locked>> | 94% | 56,840 psi | 89% | 3035 fps | 99.7% |
| IMR 8208 XBR | <<locked>> | 90% | 56,782 psi | 89% | 2969 fps | 99.9% |
| Lovex D073.5 | <<locked>> | 86% | 57,493 psi | 90% | 2963 fps | 100% |
| Lovex D073.6 | <<locked>> | 92% | 56,913 psi | 89% | 2992 fps | 100% |
| Lovex S060 | <<locked>> | 92% | 57,551 psi | 90% | 2940 fps | 99.6% |
| Lovex S062 | <<locked>> | 96% | 57,479 psi | 90% | 2989 fps | 100% |
| Lovex S065ᴾ | <<locked>> | 100% | 53,156 psi | 83% | 2920 fps | 97.2% |
| Norma 201 | <<locked>> | 92% | 56,231 psi | 88% | 2959 fps | 99.9% |
| Norma 202 | <<locked>> | 92% | 56,724 psi | 89% | 2966 fps | 100% |
| Norma 203B | <<locked>> | 94% | 54,534 psi | 85% | 2989 fps | 99.4% |
| Norma URPᴾ | <<locked>> | 100% | 48,022 psi | 75% | 2920 fps | 97.5% |
| Ramshot Big Game | <<locked>> | 94% | 55,085 psi | 86% | 3012 fps | 99.4% |
| Ramshot TAC | <<locked>> | 90% | 57,711 psi | 90% | 2986 fps | 98.1% |
| Ramshot Wild Boar | <<locked>> | 90% | 56,623 psi | 89% | 3002 fps | 99.6% |
| Ramshot X-Terminator | <<locked>> | 86% | 54,752 psi | 86% | 2920 fps | 99.3% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 35,230 psi | 55% | 1841 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 86% | 56,710 psi | 89% | 2959 fps | 100% |
| ReloadSwiss RS 50 | <<locked>> | 96% | 57,116 psi | 90% | 2982 fps | 97.2% |
| ReloadSwiss RS 52 | <<locked>> | 92% | 55,550 psi | 87% | 3071 fps | 99.2% |
| ReloadSwiss RS 60 | <<locked>> | 98% | 54,984 psi | 86% | 3100 fps | 100% |
| ReloadSwiss RS 62ᴾ | <<locked>> | 100% | 47,877 psi | 75% | 2946 fps | 97.3% |
| ReloadSwiss RS 70ᴾ | <<locked>> | 100% | 48,834 psi | 77% | 2963 fps | 96.7% |
| Rottweil R 901 | <<locked>> | 90% | 57,406 psi | 90% | 2949 fps | 100% |
| Rottweil R 902 | <<locked>> | 94% | 56,710 psi | 89% | 2956 fps | 99.9% |
| Rottweil R 903 | <<locked>> | 98% | 54,679 psi | 86% | 2982 fps | 99.7% |
| Shooters World Long Rifleᴾ | <<locked>> | 100% | 53,156 psi | 83% | 2920 fps | 97.2% |
| Shooters World Match Rifle | <<locked>> | 92% | 56,913 psi | 89% | 2992 fps | 100% |
| Shooters World Precision | <<locked>> | 96% | 57,479 psi | 90% | 2989 fps | 100% |
| Shooters World Tactical Rifle | <<locked>> | 84% | 56,434 psi | 88% | 2923 fps | 99.8% |
| SNPE Vectan SP 10 | <<locked>> | 82% | 55,695 psi | 87% | 2949 fps | 100% |
| SNPE Vectan SP 11 | <<locked>> | 98% | 56,695 psi | 89% | 3045 fps | 99.6% |
| SNPE Vectan SP 3 | <<locked>> | 84% | 55,811 psi | 87% | 2904 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 90% | 55,753 psi | 87% | 2959 fps | 98.2% |
| SNPE Vectan SP 9 | <<locked>> | 92% | 56,173 psi | 88% | 2986 fps | 99.5% |
| SNPE Vectan Tubal 3000 | <<locked>> | 90% | 55,129 psi | 86% | 2861 fps | 100% |
| SNPE Vectan Tubal 5000 | <<locked>> | 96% | 54,723 psi | 86% | 2851 fps | 100% |
| SNPE Vectan Tubal 7000ᴾ | <<locked>> | 100% | 53,722 psi | 84% | 2871 fps | 95.8% |
| Somchem S321 | <<locked>> | 86% | 54,592 psi | 86% | 2953 fps | 99.9% |
| Somchem S335 | <<locked>> | 92% | 57,363 psi | 90% | 2900 fps | 100% |
| Somchem S341 | <<locked>> | 90% | 54,984 psi | 86% | 2949 fps | 99.4% |
| Somchem S355 | <<locked>> | 98% | 55,317 psi | 87% | 2982 fps | 99.7% |
| Somchem S365ᴾ | <<locked>> | 100% | 42,772 psi | 67% | 2867 fps | 99.2% |
| Vihtavuori N130 | <<locked>> | 86% | 54,694 psi | 86% | 2825 fps | 100% |
| Vihtavuori N133 | <<locked>> | 90% | 55,085 psi | 86% | 2844 fps | 100% |
| Vihtavuori N135 | <<locked>> | 94% | 55,956 psi | 88% | 2927 fps | 100% |
| Vihtavuori N140 | <<locked>> | 94% | 57,348 psi | 90% | 2943 fps | 100% |
| Vihtavuori N150ᴾ | <<locked>> | 100% | 57,101 psi | 89% | 2963 fps | 100% |
| Vihtavuori N160ᴾ | <<locked>> | 100% | 50,560 psi | 79% | 2920 fps | 97.9% |
| Vihtavuori N530 | <<locked>> | 90% | 57,624 psi | 90% | 2972 fps | 100% |
| Vihtavuori N540 | <<locked>> | 94% | 55,564 psi | 87% | 2940 fps | 100% |
| Vihtavuori N550ᴾ | <<locked>> | 100% | 49,690 psi | 78% | 2927 fps | 97.6% |
| Winchester 6.5 StaBALLᴾ | <<locked>> | 100% | 51,764 psi | 81% | 2910 fps | 99.5% |
| Winchester 748 | <<locked>> | 90% | 57,000 psi | 89% | 3018 fps | 100% |
| Winchester StaBALL Match | <<locked>> | 92% | 55,782 psi | 87% | 2992 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% | 43,004 psi | 67% | 2684 fps | 100% |
| Accurate 2460 | <<locked>> | 80% | 46,891 psi | 73% | 2789 fps | 100% |
| Accurate 2495 | <<locked>> | 80% | 35,476 psi | 56% | 2589 fps | 100% |
| Accurate 2520 | <<locked>> | 80% | 42,003 psi | 66% | 2736 fps | 99.6% |
| Accurate 4064 | <<locked>> | 80% | 33,533 psi | 53% | 2569 fps | 98.9% |
| Accurate 4350 | <<locked>> | 94% | 39,088 psi | 61% | 2749 fps | 95.3% |
| Accurate LT-30 | <<locked>> | 80% | 51,285 psi | 80% | 2769 fps | 100% |
| Accurate LT-32 | <<locked>> | 80% | 51,663 psi | 81% | 2792 fps | 100% |
| ADI AR 2206H | <<locked>> | 80% | 39,624 psi | 62% | 2690 fps | 96.8% |
| ADI AR 2208 | <<locked>> | 84% | 38,218 psi | 60% | 2641 fps | 95.6% |
| ADI AR 2219 | <<locked>> | 80% | 51,808 psi | 81% | 2887 fps | 100% |
| ADI Benchmark 8208 | <<locked>> | 80% | 41,626 psi | 65% | 2707 fps | 98.4% |
| Alliant AR-Comp | <<locked>> | 80% | 40,741 psi | 64% | 2710 fps | 100% |
| Alliant Power Pro 1200-R | <<locked>> | 80% | 48,312 psi | 76% | 2913 fps | 99.1% |
| Alliant Power Pro 2000-MR | 51.3 gr | 82% | 38,218 psi | 60% | 2753 fps | 95% |
| Alliant Reloder- TS 15.5 | <<locked>> | 80% | 32,837 psi | 51% | 2549 fps | 95.6% |
| Alliant Reloder-10x | <<locked>> | 80% | 48,588 psi | 76% | 2789 fps | 100% |
| Alliant Reloder-15 | <<locked>> | 82% | 37,724 psi | 59% | 2664 fps | 95.6% |
| Alliant Reloder-16 | <<locked>> | 94% | 39,523 psi | 62% | 2759 fps | 95.3% |
| Alliant Reloder-17 | <<locked>> | 86% | 34,505 psi | 54% | 2664 fps | 95.3% |
| Baschieri & Pellagri 106 | <<locked>> | 80% | 50,372 psi | 79% | 2762 fps | 100% |
| Baschieri & Pellagri 107 | <<locked>> | 80% | 38,406 psi | 60% | 2677 fps | 95.1% |
| Bofors RP3 | <<locked>> | 80% | 32,227 psi | 51% | 2546 fps | 95.5% |
| Hodgdon Benchmark | <<locked>> | 80% | 43,482 psi | 68% | 2700 fps | 99.1% |
| Hodgdon BL-C2 | <<locked>> | 80% | 39,813 psi | 62% | 2717 fps | 98.6% |
| Hodgdon CFE223 | <<locked>> | 80% | 43,685 psi | 68% | 2854 fps | 97.3% |
| Hodgdon H322 | <<locked>> | 80% | 47,398 psi | 74% | 2818 fps | 100% |
| Hodgdon H335 | <<locked>> | 80% | 48,312 psi | 76% | 2841 fps | 100% |
| Hodgdon H380 | <<locked>> | 86% | 40,669 psi | 64% | 2720 fps | 95.1% |
| Hodgdon H4895 | <<locked>> | 80% | 39,943 psi | 63% | 2703 fps | 97.5% |
| Hodgdon Hybrid 100V | <<locked>> | 92% | 33,924 psi | 53% | 2592 fps | 95.2% |
| Hodgdon LEVERevolution | <<locked>> | 80% | 35,607 psi | 56% | 2654 fps | 96.7% |
| Hodgdon TrailBoss | <<locked>> | 80% | 25,788 psi | 40% | 1604 fps | 100% |
| Hodgdon VARGET | <<locked>> | 80% | 38,305 psi | 60% | 2651 fps | 96.9% |
| IMR 3031 | <<locked>> | 80% | 38,943 psi | 61% | 2710 fps | 100% |
| IMR 4064 | <<locked>> | 82% | 37,565 psi | 59% | 2618 fps | 95.6% |
| IMR 4166 Enduron | <<locked>> | 90% | 51,851 psi | 81% | 2858 fps | 95.4% |
| IMR 4198 | <<locked>> | 80% | 49,023 psi | 77% | 2753 fps | 100% |
| IMR 4451 Enduron | <<locked>> | 96% | 51,242 psi | 80% | 2877 fps | 95.1% |
| IMR 4831 | <<locked>> | 96% | 40,277 psi | 63% | 2756 fps | 95.7% |
| IMR 4895 | <<locked>> | 80% | 36,318 psi | 57% | 2644 fps | 95.9% |
| IMR 8208 XBR | <<locked>> | 80% | 41,626 psi | 65% | 2707 fps | 98.4% |
| Lovex D073.5 | <<locked>> | 80% | 46,731 psi | 73% | 2795 fps | 99.7% |
| Lovex D073.6 | <<locked>> | 80% | 38,058 psi | 60% | 2667 fps | 99% |
| Lovex S060 | <<locked>> | 80% | 40,190 psi | 63% | 2631 fps | 97% |
| Lovex S062 | <<locked>> | 80% | 35,070 psi | 55% | 2572 fps | 96.9% |
| Lovex S065 | <<locked>> | 94% | 44,338 psi | 69% | 2762 fps | 95.1% |
| Norma 201 | <<locked>> | 80% | 38,696 psi | 61% | 2641 fps | 97.9% |
| Norma 202 | <<locked>> | 80% | 38,841 psi | 61% | 2661 fps | 99.5% |
| Norma 203B | <<locked>> | 80% | 34,911 psi | 55% | 2602 fps | 95.3% |
| Norma URP | <<locked>> | 94% | 39,552 psi | 62% | 2749 fps | 95.2% |
| Ramshot Big Game | <<locked>> | 82% | 36,709 psi | 58% | 2664 fps | 95.6% |
| Ramshot TAC | <<locked>> | 82% | 44,353 psi | 70% | 2756 fps | 95.3% |
| Ramshot Wild Boar | <<locked>> | 80% | 40,683 psi | 64% | 2720 fps | 97% |
| Ramshot X-Terminator | <<locked>> | 80% | 44,933 psi | 70% | 2749 fps | 97.9% |
| ReloadSwiss RS 14 | <<locked>> | 80% | 26,005 psi | 41% | 1644 fps | 100% |
| ReloadSwiss RS 40 | <<locked>> | 80% | 46,688 psi | 73% | 2799 fps | 99.8% |
| ReloadSwiss RS 50 | <<locked>> | 92% | 50,256 psi | 79% | 2871 fps | 95.8% |
| ReloadSwiss RS 52 | 48.5 gr | 80% | 36,579 psi | 57% | 2707 fps | 95.1% |
| ReloadSwiss RS 60 | 49.2 gr | 80% | 30,182 psi | 47% | 2552 fps | 96% |
| ReloadSwiss RS 62 | <<locked>> | 96% | 41,655 psi | 65% | 2825 fps | 95.6% |
| ReloadSwiss RS 70 | <<locked>> | 98% | 45,774 psi | 72% | 2904 fps | 95.8% |
| Rottweil R 901 | <<locked>> | 80% | 42,540 psi | 67% | 2700 fps | 99.7% |
| Rottweil R 902 | <<locked>> | 80% | 36,927 psi | 58% | 2595 fps | 97.4% |
| Rottweil R 903 | <<locked>> | 82% | 32,300 psi | 51% | 2543 fps | 95.2% |
| Shooters World Long Rifle | <<locked>> | 94% | 44,338 psi | 69% | 2762 fps | 95.1% |
| Shooters World Match Rifle | <<locked>> | 80% | 38,058 psi | 60% | 2667 fps | 99% |
| Shooters World Precision | <<locked>> | 80% | 35,070 psi | 55% | 2572 fps | 96.9% |
| Shooters World Tactical Rifle | <<locked>> | 80% | 49,284 psi | 77% | 2812 fps | 99.3% |
| SNPE Vectan SP 10 | <<locked>> | 80% | 52,272 psi | 82% | 2897 fps | 100% |
| SNPE Vectan SP 11 | <<locked>> | 84% | 35,781 psi | 56% | 2648 fps | 95.4% |
| SNPE Vectan SP 3 | <<locked>> | 80% | 49,298 psi | 77% | 2808 fps | 100% |
| SNPE Vectan SP 7 | <<locked>> | 82% | 42,221 psi | 66% | 2720 fps | 95.4% |
| SNPE Vectan SP 9 | <<locked>> | 80% | 38,087 psi | 60% | 2654 fps | 96.3% |
| SNPE Vectan Tubal 3000 | <<locked>> | 80% | 40,350 psi | 63% | 2615 fps | 99.6% |
| SNPE Vectan Tubal 5000 | <<locked>> | 80% | 33,199 psi | 52% | 2470 fps | 99.2% |
| SNPE Vectan Tubal 7000 | <<locked>> | 98% | 50,183 psi | 79% | 2815 fps | 95% |
| Somchem S321 | <<locked>> | 80% | 44,614 psi | 70% | 2785 fps | 99.2% |
| Somchem S335 | <<locked>> | 80% | 39,813 psi | 62% | 2615 fps | 99.9% |
| Somchem S341 | <<locked>> | 80% | 39,102 psi | 61% | 2664 fps | 96.5% |
| Somchem S355 | <<locked>> | 82% | 33,460 psi | 52% | 2556 fps | 95.3% |
| Somchem S365 | <<locked>> | 90% | 30,966 psi | 49% | 2579 fps | 95.6% |
| Vihtavuori N130 | <<locked>> | 80% | 45,672 psi | 72% | 2690 fps | 100% |
| Vihtavuori N133 | <<locked>> | 80% | 40,480 psi | 63% | 2615 fps | 100% |
| Vihtavuori N135 | <<locked>> | 80% | 35,853 psi | 56% | 2592 fps | 100% |
| Vihtavuori N140 | <<locked>> | 80% | 36,622 psi | 57% | 2592 fps | 99.4% |
| Vihtavuori N150 | <<locked>> | 80% | 29,631 psi | 46% | 2434 fps | 95.4% |
| Vihtavuori N160 | <<locked>> | 94% | 41,568 psi | 65% | 2756 fps | 95.7% |
| Vihtavuori N530 | <<locked>> | 80% | 41,568 psi | 65% | 2700 fps | 98.5% |
| Vihtavuori N540 | <<locked>> | 80% | 35,375 psi | 55% | 2579 fps | 98.9% |
| Vihtavuori N550 | <<locked>> | 94% | 40,770 psi | 64% | 2756 fps | 95.3% |
| Winchester 6.5 StaBALL | <<locked>> | 88% | 34,737 psi | 54% | 2569 fps | 95.6% |
| Winchester 748 | <<locked>> | 80% | 40,480 psi | 63% | 2740 fps | 98.9% |
| Winchester StaBALL Match | <<locked>> | 80% | 37,231 psi | 58% | 2651 fps | 96.8% |
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 94 powders for .300 RCM loaded with the .308 | 150gr | Lapua Mega. Alliant Power Pro 2000-MR delivers the highest muzzle velocity at 3,133 fps; across all powders the maximum-charge window runs from 1,798 fps to 3,133 fps. Accurate 4350 gives the best case fill at 100 %, and 94 of the 94 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (440 MPa), the top charges use 55–90 %, leaving at least 10 % headroom. The 150.0 gr projectile in 0.308" calls for a 1:11.5 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, ReloadSwiss RS 60 rank at the top here: for .300 RCM with the .308 | 150gr | Lapua Mega 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.