BB weights explained — 0.20 vs 0.25 vs 0.28 vs 0.32+

Bottom line

0.25g for CQB and short-range woodland. 0.28g as the all-round skirmish weight. 0.32g for outdoor woodland regulars who want range. 0.36g+ for DMRs and snipers. 0.20g only for indoor pistol work or because your site requires it.

Use the wrong weight and your gun underperforms. Use the right weight and a £180 AEG outshoots a £400 one running 0.20g.

What the weight actually changes

A BB leaves the barrel at a velocity set by the gun (spring, cylinder volume, nozzle, hop). The energy of that BB is determined by both velocity and mass:

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Energy (joules) = ½ × mass (kg) × velocity² (m/s)

Heavier BB at the same gun = lower velocity, but more total energy because the gun is doing the same amount of mechanical work either way. More energy = more range, more stability in wind, less deflection off leaves and twigs.

The hop unit puts backspin on the BB. The lift the BB experiences depends on its mass relative to drag. A heavier BB carries that backspin further, deflects less, and lands closer to where you aimed.

The weights, in order

0.20g — the "house" BB

The default rental BB at most UK sites. Cheap, light, and the only weight that makes sense for indoor pistol play where engagement distances are 5–10m.

Use it for: Indoor pistol games. Sites that explicitly require 0.20g. Chrono test BBs (because that's the weight FPS limits are quoted in).

Don't use it for: Anything else, if you have a choice. A 0.20g BB out of a typical 350 FPS AEG flies for about 35m before it loses lift and tumbles. The same gun on 0.28g will reach 50m+ with usable accuracy.

0.25g — the indoor / CQB workhorse

The most common CQB BB. Light enough not to bruise at close range, heavy enough to maintain accuracy past the rental kit's effective range. Many indoor sites mandate 0.25g maximum, especially below 300 FPS limits.

Use it for: CQB, pistols you're shooting under 15m, lower-FPS rentals.

0.28g — the all-round skirmish standard

The single most useful BB weight for outdoor UK skirmishing with a stock AEG running 320–350 FPS. Better wind resistance than 0.25g, doesn't tank velocity the way 0.32g does on lower-energy systems, and still cycles reliably through mid-caps.

Use it for: Mixed woodland, anything where you don't know the engagement distance in advance, your first upgrade from 0.20g rental BBs.

This is where most skirmishers should default. If you take only one bag of BBs to a new site, take 0.28g.

0.30g – 0.32g — DMR weight

Once you cross the 1.13J / 350 FPS line, you're DMR territory at most UK sites. Heavier BBs hold their energy further out and resist wind better. Trade-off: hop adjustment becomes more sensitive, and a marginally tuned gun may struggle to lift them consistently.

Use it for: DMR/sniper systems, AEGs with upgraded hop / barrel running over 1J, ranges you expect 40m+.

0.36g – 0.40g — long-range woodland

Mostly used by bolt-action snipers running 2.3J or higher. Some HPA DMR setups too. At this weight the BB carries serious downrange energy, but it needs a precision hop, a tight inner barrel, and consistent air delivery to fly true.

Use it for: Bolt-action snipers, high-end DMRs.

0.43g+ — heavy sniper

The territory of dedicated bolt-action rifles with custom builds. Players running 0.43g BBs out of a 2.3J VSR-10 are doing something specific — usually trying to land hits at 60m+ in unpredictable wind.

Use it for: Dedicated sniper builds, with the tech work to back it up.

Joule creep — the trap you'll hit if you ignore it

Here's the thing site operators care about and most newcomers don't understand:

The same gun fires heavier BBs with more total energy, not less.

A gun that chronos at exactly 1.13J with 0.20g BBs (the UK AEG limit, roughly 350 FPS) might chrono at 1.30–1.40J with 0.30g BBs. That's because the gun's gas-piston system has more time to push the heavier, slower-moving BB while it's in the barrel.

This is joule creep. It's a real physics phenomenon, and it's why:

• Sites chrono with the BB weight you'll actually be using, not just 0.20g
• DMR/sniper roles have separate, lower joule limits than FPS limits suggest
• "I'm under FPS so I'm fine" can be wrong if you've switched BB weights since chrono

If you're switching from 0.25g to 0.32g, re-chrono before you play. Most sites will let you do this between games. If you're upgrading your gun's hop and barrel, re-chrono with your new BB weight.

Bio vs non-bio BBs

In the UK, almost every site mandates biodegradable BBs for outdoor woodland sites. This is non-negotiable at most sites — bring non-bio and you'll be sent to the shop to buy bio.

• Bio BBs decompose over months to years depending on conditions. They cost a few quid more per bag.
• Non-bio BBs are fine for indoor CQB sites where BBs are swept up after games.

When buying, "biodegradable" labelled BBs from reputable brands (BLS, ASG Open Blaster, Madbull, G&G, Geoffs) are the standard. Avoid bargain-bucket bags from unknown brands — sub-mm tolerances on cheap BBs will jam hop units and stuck shells will mash your inner barrel.

What to buy

For a starter loadout:

• 1 bag of 0.28g bio (1kg, ~3,500 BBs) — your daily driver
• 1 bag of 0.25g bio (1kg) — for CQB or as a backup
• 1 small bottle of 0.20g — for chrono and indoor pistol

Total under £25. That's enough BBs for 6–8 full skirmish days.

Sources & next steps

• FPS, joules and chronos — how site limits really work
• How to read an airsoft gun spec sheet — why "FPS with 0.20g" tells you less than you think
• Browse BB stock in the catalogue →