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505 Gibbs Load Data & Ballistics Calculator

Estimate chamber pressure and muzzle velocity for the 505 Gibbs with the free, in-browser MyLoads internal-ballistics simulator. The figures below are illustrative estimates from a physics model — not a recommended recipe. Always cross-check a current published loading manual.

505 Gibbs reference

Maximum average pressure (MAP)2,700 BAR
Nominal case capacity179.0 gr H₂O
Groove / bullet diameter0.504 in (12.80 mm)

Example simulation illustrative

Bullet
Hornady 0.505 525 gr DGS (505 Gibbs)
Powder
IMR 7828
Charge
131.6 gr
Barrel
24 in

Muzzle velocity

2,257 fps

Peak chamber pressure (interval, ±10% burn-rate)

28,990 – 37,824 – 48,179 psi

nominal is 97% of the 39,160 psi maximum average pressure

This sample load runs near the maximum average pressure for the 505 Gibbs (about 97% of MAP at the nominal estimate; the upper interval can exceed it). It is shown only to illustrate the simulator — reduce the charge and work up from your manual's start load.

Illustrative example — every figure here is an estimate and can be wrong. Always consult a current published loading manual, and never trust these numbers on their own.

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