BB weight FPS converter
Convert a chrono reading on 0.20 g BBs to the velocity you’ll get with 0.25 g, 0.28 g and heavier.
0.00J
| Weight | m/s | fps |
|---|---|---|
| 0.12 g | ||
| 0.20 g | ||
| 0.23 g | ||
| 0.25 g | ||
| 0.28 g | ||
| 0.30 g | ||
| 0.32 g | ||
| 0.36 g | ||
| 0.40 g | ||
| 0.43 g | ||
| 0.45 g | ||
| 0.48 g |
Why heavier BBs leave the barrel slower
An airsoft gun delivers roughly the same energy to the BB regardless of its weight. Put that energy into a heavier BB and the velocity drops.
v₂ = v₁ × √(m₁ / m₂)
Example: 350 fps on 0.20 g becomes 350 × √(0.20/0.25) ≈ 313 fps on 0.25 g and about 296 fps on 0.28 g. The energy stays at 1.14 J.
Why fields chrono on 0.20 g
A single reference weight makes every gun comparable. The field's limit is really an energy limit; the fps number is just the easy way to check it with the BBs they hand you at the chrono station.
Why you'd still use heavier BBs
- Less affected by wind and drag, so the flight path is more consistent
- Hop-up grips them better, which usually extends effective range
- They keep more energy downrange
Joule creep. Some hop-up designs (and most gas guns) give heavier BBs more energy than the formula predicts. A gun that reads under the limit on 0.20 g can be over on 0.28 g. If your field allows heavy BBs, chrono with the weight you actually play with.
Picking a weight
| Weight | Typical use |
|---|---|
| 0.12 g | Low-power springers and youth guns |
| 0.20 g | The chrono standard. CQB and stock AEGs |
| 0.25 g | The everyday choice in Japan; good balance of range and stability |
| 0.28–0.30 g | Outdoor AEGs and gas blowback rifles |
| 0.36 g and up | Bolt-action sniper rifles and DMRs |