Effective range estimate
Rough effective range from muzzle energy and BB weight.
0m
What actually sets range
Range is decided by muzzle energy, BB weight and how well the hop-up is tuned, not by fps alone. The same 0.9 J gun drops BBs at 30 m with a bad hop and reaches close to 50 m with a good one.
Hop-up in one paragraph
The hop-up rubber puts backspin on the BB. Backspin creates lift that cancels gravity for a while, so the BB flies flat and then falls off at the end. Too little spin and it drops early; too much and it climbs and stalls.
Why heavier BBs reach further
They leave the barrel slower but keep their spin and momentum longer, and wind pushes them around less. Under Japan's 0.98 J limit, 0.25 g is the usual sweet spot; guns with strong hop handle 0.28 g well. At 1.3–1.5 J (common US and UK AEG limits), 0.28–0.32 g is normal.
How this estimate works
The tool is an empirical fit anchored on "about 45 m effective at 0.9 J on 0.25 g with a tuned hop", which is the rule of thumb at Japanese fields. Expect ±10 m in real life from wind, BB quality and barrel cleanliness.
Effective range is not the same as a reliable hit. If your BBs reach 40 m, you can count on hitting a player-sized target at roughly 70–80% of that.