How does an Airsoft Grenade Launcher Work?

21st Aug 2017

How does an Airsoft Grenade Launcher Work?

In a previous blog of ours, we looked at how airsoft grenades work – from pyrotechnic, to gas and blank firing grenades. One area that we didn’t cover was 40mm grenades and launchers.

40mm airsoft grenades are a fun and useful tool to use in airsoft, spraying up to 200 BBs instantly towards the enemy.

So, how do they work?

An airsoft grenade consists of 3 very simple parts to understand, the gas reservoir the BB chambers, and the valve.

The Gas Reservoir

The gas reservoir is – without going into too much detail – a reservoir for gas. You charge the grenade up via the fill valve (usually on the dangerous end), with your propellant gas of choice. Abbey vertex gas is our most powerful and perfect for this application.

The grenade is filled with gas in the same way that you would fill a gas pistol or rifle magazine, explained in our video here.

Note: Ensure that when charging the grenade with gas that you are wearing eye protection, even if the chambers are empty. You never know what kind of debris (or even high pressure gas) could damage your eyes if accidentally discharged.

The BB Chambers

The “front towards enemy” end can be viewed similarly to any other airsoft gun, except instead of 1 BB in the chamber, there can be 20 BBs and instead of 1 chamber, there’re about 10 – giving (in some cases) 200 BBs ready to be fired.

The end of the barrels usually have an O-ring which hold the BBs in place and cause them to spread, much like a hop-up when fired causing a wider spread of BBs.

Note: Ensure that when loading the BB chambers with BBs that you are wearing eye protection, even if you believe there is no gas within the chamber.

So how are the BBs propelled from the barrels?

The Valve

The grenade will usually have a large push button on the back which actuates an internal valve. The internal valve opens the gas reservoir and directs the pressure into the rear of the BB chambers. This pressure forces the BBs out of the chambers and out towards the enemy with a commanding and satisfying “THUNK”…

ALL of the gas within the reservoir is used to propel the BBs. Unlike pistol and rifle gas chambers, which only use a small portion, you need to refill the reservoir (and BB chambers) before next use.


Whilst you can theoretically use a 40mm grenade without a launcher, you should probable pair it with a 40mm launcher. This can be anything from a little handheld launcher to an under slung m203 or a standalone revolving CAW launcher.

You place the grenade inside its individual chamber and pull the trigger. The launcher will then depress the 40mm grenades button and actuate the valve.


Tip #1 - If you find that you aren’t quite getting the range that you would like to from your 40mm grenades, try loading them with less BBs. There is a trade-off between volume and range, so try to find the ratio that works for you and your play style.

Tip #2 - 40mm Gas grenades are very similar to gas magazines, so all of the maintenance tips and guides are applicable. Ensure that you keep them gassed up in storage with something like Maintenance Gas, to ensure that they remain in tip top condition. The O-rings that simply hold the BBs in place aren’t too important, but if they dry up they may snap and allow BBs to escape.

Tip #3 - Do you load BBs or Gas First? It’s a hot debate. By loading the gas last, you have the potential to trip the valve and shoot the entire load of BBs everywhere. By loading BBs last, you have a greater potential (due to how long it takes) to shoot 1 or all of your BBs everywhere, depending on how far loaded you are.

This one is down to personal preference, as long as you’re doing it in the correct environment, being safe and wearing eye protection, you’ll be fine.

Tip #4 – There’s a temptation to store the grenade ready-to-go in the launcher, which makes every bit of sense. You have your magazine ready to go in your gun, why not the grenade ready in the launcher? The problem with this is that the majority of the time it’s spent facing the ground, whist running, jumping and rolling around. This has the tendency to allow BBs to fall out of their chambers (they’re only loosely held in, remember). Leading to the awkward situation of going to fire the grenade and only 5 BBs coming out.

Keep the grenades facing upright in a readily accessible pouch and load when ready. It doesn’t have to be ‘in the moment’ right there and then, but 5 minutes before hand is better than 4 hours before hand.

Tip#5 – Just use it. You’ll often spend most of your time looking for the ‘perfect’ moment to use it. Don’t worry about it. Use it whenever, there’s plenty of gas and BBs available to reload it quickly and use it again.

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