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BBs are the one thing every airsoft player buys again and again, and they are the most underrated part of your setup. The right BB weight and quality can transform your range and accuracy. The wrong ones cause jams, flyers and even damage your gun. Here is what you need to know.

BB basics

Almost all airsoft guns fire 6mm plastic BBs. (A few rare guns use 8mm, but you are very unlikely to meet one.) Good quality BBs are manufactured to a diameter of around 5.95mm with a tolerance of about ±0.01mm, and they are polished and seamless. They come in different weights, measured in grams, and that weight makes a big difference.

BB weights and what they do

Why heavier BBs are often better

Heavier BBs carry their momentum further, are less affected by wind and are more stable in flight. They also hit a little harder at range. The trade-off is that they leave the barrel slower and need more hop-up to stay level. Too heavy for your gun, and they will drop short.

Energy, not just fps

Sites usually quote power limits in fps using 0.20g BBs, but what actually matters is energy in joules. A gun shooting 350 fps with a 0.20g BB (about 1.14 joules) will shoot roughly 313 fps with a 0.25g BB. The energy stays roughly the same, while the heavier BB flies more consistently. That is why most players move up from 0.20g once they have chronographed.

Biodegradable BBs

Most UK outdoor sites now require biodegradable BBs, and some only allow BBs bought on site. Bio BBs are made from plant-based plastics designed to break down in soil over time. They are not instant: they still take months or longer to degrade, which is why they should never be left lying around at home or in public places.

Indoor CQB sites usually allow standard non-bio BBs because they sweep them up.

Good bio BBs now perform just as well as standard ones. Store them in a sealed bag, away from damp and heat, as moisture can affect them over time.

Tracer BBs

Tracer BBs contain a luminous pigment that glows briefly when charged by a bright flash from a tracer unit fitted to your muzzle. They are brilliant for night games and for seeing where your shots are going during the day in shaded woodland. Use them with a tracer unit from our suppressors and tracer units range, and check whether your site allows them.

Why quality matters

Cheap, poorly made BBs are a false economy. Problems include:

• Seams and bubbles from poor moulding, which make BBs fly unpredictably (“flyers”).
• Inconsistent sizes and weights, which ruin accuracy.
• Shattering inside the hop-up chamber, which can cause jams and damage your bucking or gearbox.
• Dust and residue that build up in your inner barrel.

To check a bag, tip some onto a flat surface: good BBs are uniform, shiny and without visible seams. Roll a few across a table, and they should run straight.

Golden rules

1. Never reuse BBs picked up from the ground. Even tiny scratches or dirt can jam your gun.
2. Buy reputable brands, and stick with one once you have tuned your hop-up.
3. Buy in bulk to save money. A 4kg or 5kg box works out much cheaper per BB.
4. Store BBs sealed and dry.
5. Check site rules on bio BBs, tracers and maximum weights before game day.
6. Pick up spilled BBs at home. They are a slip hazard and harmful to pets if eaten.

How many BBs will you use?

It depends hugely on play style. A careful rifleman might use 1,000 to 2,000 BBs in a day, a support gunner many more, and a sniper a few hundred. A 1kg bag of 0.25g BBs contains about 4,000 rounds. For a full cost breakdown, see is airsoft expensive?

Frequently asked questions