Chrono calculator

Manufacturers rate velocity on 0.20g BBs. Fields limit muzzle energy. Since energy stays constant as BB weight changes, a gun that reads 400 FPS on 0.20g reads about 316 FPS on 0.32g — same joules, same rule.

Chrono check

Rated 400 FPS on 0.20g — 1.49 J at the muzzle. Energy is fixed; velocity changes with BB weight.

BB weight

400 fps

on 0.20g · 1.49 joules

Field limits

CQB / indoorOver by 0.35 J
Outdoor AEGPass · 0.00 J spare
DMR(75 ft MED)Pass · 0.39 J spare
Bolt-action sniper(100 ft MED)Pass · 0.84 J spare

Brackets are typical US field categories. Always confirm your own field's published limit — some run lower, and chrono readings vary with hop-up and gas temperature.

The math

Kinetic energy is ½mv², so velocity scales with the inverse square root of BB mass. Chrono readings also drift with hop-up setting, gas temperature, and barrel wear — treat any published figure as a starting point, not a guarantee.