Load Specifications
Load data in caliber 6.5 x 52 R with .258 | 85gr | Rim Rock RNFP Cowboy bullet and 8 powders. The key underlying parameters are shown in the table above. The recommended powders for this cartridge and bullet combination are Alliant AR-Comp, ReloadSwiss RS 14 and Hodgdon TrailBoss.
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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Max Load - Barrel Length: 23.62"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 2015 | <<locked>> | 86% | 30,966 psi | 87% | 2562 fps | 96.2% |
| Accurate 2495 | <<locked>> | 96% | 31,357 psi | 88% | 2654 fps | 96.9% |
| Alliant AR-Comp | <<locked>> | 88% | 30,690 psi | 86% | 2638 fps | 98.6% |
| Alliant Reloder-10x | <<locked>> | 82% | 31,879 psi | 90% | 2602 fps | 97.7% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 31,444 psi | 88% | 1795 fps | 100% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 31,096 psi | 88% | 1834 fps | 100% |
| Vihtavuori N130 | <<locked>> | 82% | 30,632 psi | 86% | 2510 fps | 97% |
| Vihtavuori N135 | <<locked>> | 94% | 31,691 psi | 89% | 2635 fps | 96.7% |
Recommended = one of the top powders for this cartridge and bullet combination.
Start Load - Barrel Length: 23.62"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Accurate 2015 | <<locked>> | 84% | 28,921 psi | 81% | 2507 fps | 95.3% |
| Accurate 2495 | <<locked>> | 92% | 27,137 psi | 76% | 2539 fps | 95.1% |
| Alliant AR-Comp | 24.1 gr | 80% | 23,511 psi | 66% | 2405 fps | 95.1% |
| Alliant Reloder-10x | <<locked>> | 80% | 29,747 psi | 84% | 2546 fps | 96.9% |
| Hodgdon TrailBoss | 8.4 gr | 80% | 22,887 psi | 64% | 1601 fps | 100% |
| ReloadSwiss RS 14 | 8.5 gr | 80% | 22,350 psi | 63% | 1634 fps | 100% |
| Vihtavuori N130 | <<locked>> | 80% | 28,645 psi | 81% | 2457 fps | 96.2% |
| Vihtavuori N135 | <<locked>> | 90% | 28,007 psi | 79% | 2533 fps | 95% |
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 24 powders for 6.5 x 52 R loaded with the .258 | 85gr | Rim Rock RNFP Cowboy. Accurate 4064 delivers the highest muzzle velocity at 2,664 fps; across all powders the maximum-charge window runs from 1,795 fps to 2,664 fps. Hodgdon TrailBoss gives the best case fill at 100 %, and 24 of the 24 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (245 MPa), the top charges use 85–90 %, leaving at least 10 % headroom. Hodgdon TrailBoss, ReloadSwiss RS 14 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 AR-Comp, ReloadSwiss RS 14, Hodgdon TrailBoss rank at the top here: for 6.5 x 52 R with the .258 | 85gr | Rim Rock RNFP Cowboy they combine a high case fill with complete burn and sit in the upper velocity band. As outliers, Accurate 2460, Accurate 2520, Accurate 4064 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.