What is a NBB (Non Blow-Back)?

What is a NBB (Non Blow-Back)?

The Non Blow-Back is a fairly simple system using expanding gasses to propel a BB. The reloading mechanism is usually powered by the shooters finger during the trigger-pull, which can make the trigger a lot harder to pull than on GBBs.

The most popular applications for the NBB mechanism are revolvers, semi-automatic pistols.

What makes a NBB worth buying?

One of the main benefits of the NBB is its price. They are generally cheaper to buy than Gas Blow-Backs and they are a lot more efficient with gas.

The main benefits of the NBB are...

Reliability
NBBs are quite reliable as they use a fairly simple mechanism. However, many NBB pistols are poorly made and this can introduce reliability issues. Get a good quality one and it should work well for years.
Accuracy
The NBB mechanism actually allows for more accurate shots than the GBB. This is due mainly to the fact that all internal parts are stationary while the shot is fired. However, as many NBBs take the hammer-reset energy from the trigger, the harsh trigger-pull can cause accuracy issues. If the trigger pull is too hard, you might find that the pistol itself is pulled off course as you attempt to squeeze.
Very Compact
NBBs do not need to hold the batteries, gears, pistons or large main-springs that AEGs need to carry. They do not need the blow-back cylinder, large capacity gas tank, or space to move that is required by GBBs. This means that they can be small - very small. One of the smallest and most reliable is the Colt 25 replica.
Shown on the right here, the Colt 25 represents just how little space is required for a reliable NBB mechanism.
Light-Weight
NBBs usually have plastic bodies with cast-metal internals. This means that the NBB is quite light. It doesn't need the same size gas container as the GBB, so less metal is used there.
Cheap
The main redeeming feature of the NBB - its price! The Colt 25 pictured here costs around Ł20 in the UK and is a nice little pistol to play with. Its shots are very low in power (MUCH lower than GBBs or AEGs), but it is solid and reliable.
The NBB is also pretty cheap to run. It uses only a fraction of the amount of gas as the GBB and some of them can be just as powerful.

How does a NBB work?

The Non Blow-Back has a relatively simple layout. Without going in to a diagrammatic detail, this is the chain of events that occurs each time the NBB is shot.

1. The shooter pulls the trigger
The trigger is linked to the hammer and the reloading mechanism.
In a revolver, this means that as you pull the trigger, your pulling energy is going toward pulling the hammer back and rotating the cylinder containing all of the BBs. Most revolvers allow you to manually pull back the external hammer before firing though, giving the shooter a much easier trigger-pull.
In a semi-automatic pistol layout, the trigger-pull energy goes toward pulling back the hammer and the air nozzle pushing a BB from the magazine in to the breech. There is sometimes a manual option to 'pre-load' these before shooting, but this is not available on all models.

2. The trigger is almost completely pulled back
At this stage, the BB is in line with the barrel, the gas seals have been closed to prevent leakage and the hammer is about to be released...

3. The hammer is released
As the trigger is finally pulled all the way back, the hammer is released. It flies forward and strikes the firing valve inside. This releases a jet of gas out of the storage cylinder and directly in to the breech, behind the BB.
The BB is launched out of the barrel, while the firing valve's return spring forces the hammer to lift off, stopping the flow of gas.

4. The trigger is released
As the trigger is released, the mechanism relaxes. The pressure holding the gas seals firmly in place is released and the air nozzle (if a semi-automatic pistol type) falls back to allow another BB to fall in front of it.
Once the trigger has been fully released, the pistol is ready for another shot.

There are other types of NBB mechanism that use the same principal, but operate in a slightly different manner. This is the most common mechanism found in mid-range airsoft pistols today.

How good is it really?

Replica realism (look) :	Good, but varies. Most NBB pistols are only NBB because they are a low-cost alternative to GBB pistols, but a step up from Springers. These models usually don't look too convincing as replicas (to those with an eye for such things anyway), but they do have accurate dimensions. Some higher quality NBB pistols are very good replicas though, but you do pay for the privilege. Trademarks vary depending on the quality of the model. Serial numbers where present usually reflect the fact that these are toys (e.g. "911COP" or "CQB999", etc...)
Replica realism (feel) :	Good. The weight of the common NBB is not as heavy as its real-steel cousin, but the weight is comfortable and easy to manage. Weight really can vary, depending on the model, with some feeling as heavy as the real thing, others can feel as light as a feather. Plastic bodies can spoil the feel for the replica fanatic and there are few metal bodied NBBs available.
Replica realism (operation) :	Good. The NBB does not have the realistic 'recoil' effect of the GBB, or as loud a noise, but it does shoot shot after shot accurately without having to manually reload each time. There is usually a nice small 'pop' too. As an added bonus, the NBB is the most "silence-able" airsoft model available. There are few moving parts and the only release of gas is out of the barrel, so a good quality silencer can reduce the 'pop' to a mere dull-thud.
General build quality :	Reliability is good, but build quality varies with price.
Cost effective?	Yes. They are cheap to buy and use relatively little gas to operate.
Upgradeable?	Generally No. Most NBB pistols are not designed to be upgraded or enhanced and some have their bodies glued together in places, to stop modifications from being made.
Target shooting suitability :	Average. The NBB is great for indoor target shooting if the NBB's power level is low enough to be safe. Safety goggle should of course always be worn while shooting. However, if the power level is too low, it may not pierce a paper target. Outdoors, only a higher powered NBB would be good for target shooting, as most models would be too badly affected by wind.
Skirmish suitability :	Good, if the power level is high enough to be accurate at the ranges you will be using. If the power level is too low, the opposition will be able to shoot you, long before you can hit them.
Target audience :	Those that want a good balance between a cheap gun and a fun gun to shoot. A good one will cost a bit more, but will be better for skirmishing. A cheap one will be lots of fun in the back garden, but will probably not be the best thing to use in a skirmish, unless you like the safe zone.