PCP airguns – breaking down the terminology

Many of you have probably seen Guy Ritchie’s 1998 crime comedy Lock, Stock & Two Smoking Barrels. I imagine most non-shooting filmgoers who’ve seen it are vaguely aware that the title is a reference to a double-barrelled shotgun, though few probably understand what the term actually means. The same can be said for the terminology of PCP airguns.

Most shooters will know the parts of an air rifle, but newcomers may not, so here’s a rundown of some of the basic terms. It’s not exhaustive, and I’ve concentrated on typical PCP airguns rather than a springer or gas-ram. I’ve also focused on the parts an air rifle owner will come into contact with – literally – while operating their air rifle. Maybe we’ll look at internal components in a later feature, but for now let’s examine the external parts and operating features. (Click here for our guide to improving your springer airgun setup, if you’d prefer a springer instead. If you want help making the choice between PCPs and springers, click here).

An air rifle, just like a powder-burning firearm, is composed of three basic components, these being the action (the “lock” in Ritchie’s film title), the stock and the barrel. All three must work together to fulfil the shooter’s needs. Whether any one of these three is more important than the others is a debate for the club house, the range or maybe even the pub, but in an ideal world all should work in perfect cohesion.

Just bought a PCP airgun for the first time? Don’t miss mike Morton’s advice on what to expect

The action

This is the mechanism that extracts the pellet from the magazine, inserts it into the rear of the barrel, delivers the air that fires it, then cycles the magazine and inserts a new pellet once the previous one has been fired. This collection of parts is referred to as the heart of the rifle and can be likened to the engine of a car. Several types of actions are used in pre-charged pneumatics, usually bolt-action or sidelever, as with the Weihrauch HW100 S seen here.

There’s a lot going on in this area of the rifle, with the sidelever, drop-down handle, magazine release catch, magazine rotor and pellet probe, not to mention the dovetail rail for the scope mounts

Trigger Blade

Commonly referred to just as the “trigger”, the blade is the device that transfers the input from the shooter’s trigger finger and activates the trigger itself. The height and angle of the blade can sometimes be adjusted so the blade is better positioned in relation to the pad of the trigger finger, giving the shooter more control.

Safety Catch

While some purely target-focused air rifles won’t have a safety catch, the vast majority of airguns do, blocking the full range of movement of the trigger. The catch on the HW100 S is a rocker type, the rearwards position being “Safe” and forwards “Fire”.

The location of a safety catch can vary, being placed on the side of the action, as here, the rear of the action, above the trigger guard or in front of the trigger blade. Some safeties, like the HW100’s, cannot be applied unless the rifle has been cocked.

Trigger Guard

A drop-down lever makes it far easier to locate the end of the sidelever by feel alone when the shooter’s in the aim

The trigger guard is a device that helps protect unintentional contact with the trigger blade, either from a carelessly placed finger or contact with clothing or undergrowth.

Some trigger guards are attached directly to the stock while others are attached to the action.

Diving Into The Well

There’s more to shooting a multi-shot PCP than just whacking in a magazine and squeezing the trigger. Let’s take a look at what happens inside the magazine well [1].

The magazine well is simply the area into which a detachable magazine is inserted. It must be free of obstructions, which usually means the rifle must be cocked and the pellet probe drawn back out of the way, and the magazine release catch, if one is present, should be in the release position.  In some rifles the catch is non-essential as the action will function perfectly well with a magazine inserted and the catch not engaged.

For others, such as the HW100 S seen here, applying the catch is a vital part of the process as it forces a rotor [2] to engage with the rear face of the magazine, cycling the mag and presenting subsequent pellets in line with the bore after the first one has been fired.

The pellet probe [3] is the device that drives the pellet from the magazine and into the bore with a forward stroke of the sidelever or bolt. Some pellet probes are fitted with a small O-ring to make an airtight seal before the pellet is fired, while the O-ring is located at the back of the barrel on some other rifles. This small part is vital to the gun’s operation.

Sidelever Or Bolt

The role of the sidelever or bolt in mechanical multi-shot PCP airguns is to cock the rifle and push a pellet into the barrel. When that shot has been taken it will repeat the process, this time indexing the magazine so the next pellet is lined up with the bore.

A typical bolt action usually relies on an upward, rearward, forward and downward movement, while a sidelever is quicker as it only requires a backwards and forwards movement on behalf of the shooter.

A few air rifles have a third type of action called a straight pull, which looks like a conventional turn-bolt, but only requires a backwards/forwards movement, similar to a sidelever.

Scope Mounting Rail

Scope mounts are attached to the action via a traditional dovetail rail like this or the more modern slotted Picatinny rail

Telescopic sights, and other types of sighting systems for that matter, such as dioptre or red dot, are usually attached to the action via mounts that connect to a rail. The two most common types of rail are the traditional dovetail or the more recent US military-specced Picatinny system, which features a series of transverse slots.

Some rifles have Picatinny rails that are actually mounted on top of a dovetail rail, and these can easily be removed if the user prefers the more traditional style of the dovetail system. Other rails are out-and-out hybrids, letting the shooter use the mounts of his or her choice.

The stock

The stock is the part of the air rifle that is either actually held by or comes into contact with the shooter. It also supports the action and the barrel, either directly or indirectly.

The stock, which is sometimes colloquially referred to by shooters as the “handle”, is what allows the shooter to point the barrel in the right direction in order to hit what’s being aimed at.

As with regular firearms, air rifle stocks can be made of solid wood, laminated wood or solid wood with a rubberised coating, and there are plenty that are made of synthetic materials too. The HW100 S featured here has a traditional solid walnut stock.

Butt

The butt of the stock bridges the gap between the action of the rifle and the shooter’s shoulder, and is the area where the shooter will rest their head when looking through a sight. Most rifle stocks are made of one part these days, but in those cases where the butt and forend are separate, the butt is known as the butt stock, while the forend is known as the forestock.

Scope mounts are attached to the action via a traditional dovetail rail like this or the more modern slotted Picatinny rail

Some safety catches can be applied at any time, while others can only be set to Safe when the rifle has been cocked

Butt Pad

The butt pad is designed to protect the end of the stock, absorb recoil and provide a secure anchor point for the rifle when it’s in the shooter’s shoulder. Recoil on PCP airguns is negligible, especially a sub-12 foot pound model, but springers and gas-rams can benefit from some recoil absorption.

Some butt pads have some material removed from them by the manufacturer, leaving behind a latticework that makes them more squashy and even more capable of absorbing recoil. This is known as a ventilated butt pad. Some butt pads can be raised or lowered, altering the height of the butt in the shoulder, or even angled to the side, making it easier to line up the sight.

Under Pressure

Some safety catches can be applied at any time, while others can only be set to Safe when the rifle has been cocked

Cartridge rifles and air rifles are the same inasmuch as they both use pressure to force a projectile out the end of the barrel. In the case of the cartridge rifle, the pressure comes from the explosion of the powder that’s contained inside the cartridge case, while with a PCP it’s the release of the compressed air that’s stored within the rifle itself rather than the ammo.

PCP airguns use either an inline air cylinder, like the one on the HW100 S, or a fatter cylinder, commonly referred to as a buddy bottle. This term comes from scuba diving, where divers would take a secondary air supply underwater with them to act as a “buddy” if they ran into a problem with their main air cylinder [1].

The cylinder is filled with compressed air via a charging port, which is typically either a male Foster coupling or an open port into which an appropriate filling probe must be inserted. Dust and grit are the enemies of any air rifle, and it’s important to protect the air cylinder and the charging port with some sort of dust plug, cap or collar. The one seen here is a plug type that’s made of Delrin and is held in place by an O-ring. It’s important to keep the plug clean too, otherwise you may actually be introducing grit [2].

A pressure gauge will let you see at a glance whether or not your rifle needs filling. Manufacturers will advise you of the standard working pressure and the maximum fill pressure, which may or may not be the same, and the higher pressure should never be exceeded for safety and longevity reasons.

When filling a rifle, it’s best to use the gauge on the filling apparatus, as this will typically be more accurate than the gauge on the rifle  [3], which is more of a helpful indicator.

Cheekpiece And Comb

The role of the stock is to position the butt against the shooter’s shoulder and, even more importantly, to position the eye in proper alignment with whatever sighting system is being used. While the butts of most early stocks were smooth, some featured a raised area on which the shooter could more comfortably rest their face. Stocks featuring a cheekpiece are now the norm on most airguns, and in addition to standing proud, they usually sit a little bit higher than the natural line of the butt, offering better head and eye alignment with the sight.

The very top is known as the comb, and is the last point of contact between the shooter’s face and the stock. Some cheekpieces can be raised or lowered, altering the height of the comb.

Pistol Grip

The pistol grip is chequered, and is finished off with a pale wood spacer and dark wood end cap, both traditional aesthetic embellishments

The pronounced area on the HW100 S that’s held by the shooting hand is known as the pistol grip because it rakes downwards, much like the grip on a typical handgun. This contrasts with rifle stocks that have no pistol grip, with the hand having to grasp the stock at a far shallower rake. It can take slightly longer to bring a rifle into the aim if it has a pistol grip, but some shooters find them more comfortable in the hand while offering superior control, and consider the pay-off worthwhile.

Chequering

Chequering leaves behind a raised pattern, which acts a bit like the tread of a car tyre in dispersing water so a good grip can be maintained

Most rifle stocks feature some sort of embellishment to enhance grip, which is especially important when the shooter’s hands get sweaty or it’s raining and the stock starts to feel slippery.

Chequering was traditionally cut by hand, a highly skilled and time-consuming process, but is usually carried out by laser nowadays, or can even be moulded in the case of synthetic stocks. Stippling is similar to chequering, but is of a more random texture, again to assist grip, whereas chequering can be enjoyed almost as much for its aesthetic appeal as its practicality.

A Barrel Of Fun

Chequering leaves behind a raised pattern, which acts a bit like the tread of a car tyre in dispersing water so a good grip can be maintained

While the whole barrel  is important, it’s the last part that’s truly vital as this is what will allow a pellet to fly true – or see it corkscrew away into oblivion. It needs to be looked after!    

The end of the barrel from which the pellet exits is called the muzzle, and the last point of contact between the pellet and the rifling is called the crown. Several types of crown have emerged over the years, with the simplest being the flat crown, where the crown and muzzle are flsuh to each other. Many air rifles, however, feature a recessed crown which helps protect the lands and grooves of the rifling [1].

The muzzle can be threaded on the outside so an accessory can be screwed on [2].

This will typically be a moderator, but some target shooters like to fit a muzzle brake or air stripper. If no such attachment is being used then a thread protector can be screwed in place to prevent the threads from being damaged.

Most threaded PCP barrels will have been screw-cut with a pitch known as ½” UNF (Unified Fine), but other pitch types are sometimes used. The thread on the barrel must therefore be matched to that of the device the shooter wants to screw in place.

Forend

This is the front portion of the stock that’s usually held by the leading hand, although it may be shorter than normal on some PCPs that are equipped with a buddy bottle rather than an inline air cylinder.

The forend, traditionally written as fore-end, is known as the fore stock on rifles where the stock is made up of two separate components. That type of stock is uncommon nowadays.

Final Thoughts

The “Lock” in Ritchie’s Lock, Stock & Two Smoking Barrels referred to a type of external action that was found on some older firearms before the advent of the breech-loading mechanisms that we have today. But in air rifle terms, it’s the action.

Armed with all this knowledge, someone could now make a film about air rifles, but what would they call it? Action, Stock & One Non-Smoking Barrel perhaps?