Load Specifications
Load data in caliber .455 MK II with .452 | 200gr | X-TREME X-DEF HP bullet and 4 powders. The key underlying parameters are shown in the table above.
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 ≥ 60% and propellant combustion ≥ 80%. 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: 4"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Baschieri & Pellagri 102 Pistol² | <<locked>> | 68% | 11,545 psi | 88% | 738 fps | 97.6% |
| Hodgdon TrailBossᴾ | <<locked>> | 100% | 11,400 psi | 87% | 699 fps | 99.4% |
| ReloadSwiss RS 14ᴾ | <<locked>> | 100% | 10,385 psi | 80% | 682 fps | 95.7% |
| Vihtavuori N32C Tin Star² | <<locked>> | 72% | 11,516 psi | 88% | 702 fps | 100% |
Start Load - Barrel Length: 4"
| Powder | Charge | FR | MaxP | % | V(0) | z |
|---|---|---|---|---|---|---|
| Baschieri & Pellagri 102 Pistol² | <<locked>> | 60% | 9,877 psi | 76% | 686 fps | 95.7% |
| Hodgdon TrailBoss*² | <<locked>> | 60% | 6,425 psi | 49% | 515 fps | 93.2% |
| ReloadSwiss RS 14*² | <<locked>> | 60% | 6,164 psi | 47% | 505 fps | 87.4% |
| Vihtavuori N32C Tin Star² | <<locked>> | 60% | 8,963 psi | 69% | 630 fps | 99.9% |
* not dangerous but load has suboptimal powder burnt with possible characteristics such as extensive muzzle flash or inaccurate loads.
² fill rate low - you might want to consider using a filler to ensure proper ignition.
ᴾ possible press load - work up slowly to this load while watching for signs of excessive pressure.
This overview compares 2 powders for .455 MK II loaded with the .452 | 200gr | X-TREME X-DEF HP. Hodgdon TrailBoss delivers the highest muzzle velocity at 699 fps; across all powders the maximum-charge window runs from 682 fps to 699 fps. Hodgdon TrailBoss gives the best case fill at 100 %, and 2 of the 2 powders fall inside the usable 80–100 % fill window.
Relative to the caliber's maximum pressure (90 MPa), the top charges use 80–87 %, leaving at least 13 % 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. Hodgdon TrailBoss, ReloadSwiss RS 14 stay subsonic at start load. Always begin at the start load and work up in small increments while checking case and primer for pressure signs.