Glossary of Wolverine Airsoft terms & technology


Automatic Electric Gun – An airsoft rifle powered by a gearbox consisting of gears, springs and a motor, as opposed to high pressure air. Many AEGs can be converted to HPA with an HPA “Drop-In Kit.” For example, the INFERNO Gen 2 V2 Kit can convert M4 style AEGs that use a V2 Gearbox.

Air Line

Can refer to many components between an HPA tank and the engine, including a Grip Line (the line that extends out of the engine into the grip), a Flex Line (the line that connects the grip line to the regulator), or a smaller accessory line like the Mini Airline connects the engine to a WRAITH stock.

Air Stock

Refers to on-board air solutions like the WRAITH X which integrate air supply into the buffer tube instead of a separate HPA tank and airline.


When referring to HPA airsoft guns, the centering of the nozzle, hop, and inner barrel to create a straight path for the BB. In AEG conversions, aligning can mean using shims to make small adjustments to the engine placement within the gearbox. The MTW has “Intrinsic Alignment,” meaning the upper receiver is machined precisely to hold an HPA engine with no room for movement.


The two-piece component of an INFERNO or HYDRA HPA engine that sits over the nozzle and poppet and regulates airflow during nozzle movement. More info in the corresponding owner’s manuals:



A solid block of aluminum milled out by a CNC machine to create the final part. Billet receivers are stronger than cast receivers because they are made from a single block of material as opposed to pouring molten aluminum into a mold. Many Wolverine Airsoft products are built with billet-machined parts, for example, the MTW Billet Series as well as the MTW-9, MTW-308 and Articles of Heresy Series.


The family of Wolverine Airsoft engines designed to convert bolt-action replicas to HPA. Includes the BOLT and BOLT M (Mechanical). More info:

Bolt Catch

On a real AR, the bolt catch, also known as a bolt release, locks the bolt back after the last round from the magazine is fired. Just like on a real AR, the MTW‘s bolt catch must be pressed after loading a new magazine to re-enable firing. More Info:


A rubber sleeve that fits on the inner barrel and holds the BB in place until it is fired. Wolverine Airsoft does not manufacture buckings.


Buffer Tube

The hollow tube attached to the rear of the lower receiver on which the stock can be attached. Commonly used to house an HPA gun’s battery and/or FCU.

Burst Mode

A fire mode in which a specific number of BBs are fired in succession with one trigger pull. This is a feature of the FCU.


A device used to measure FPS (feet-per-second) and joules. Sometimes referred to simply as “chrono”. Airsoft games regularly require players to “chrono” before game to meet specific requirements.

Closed Bolt

In HPA engines, a system where the nozzle rests in the forward position with a BB loaded in the hop ready to fire, as opposed to an open bolt system where the nozzle rests in the back position and fires the BB through the hop. The INFERNO Gen 2 uses a hybrid system that loads the BB into the hop, allows it to come to rest, and then fires.


CNC machining, or Computer Numerical Control machining, is a manufacturing process that uses pre-programmed software to control the movement of factory machinery. Though some parts and products include CNC in the name such as the CNC Hop and CNC Feed Tube, CNC machining is used to create many parts including billet receivers, rails, and even make final cuts in forged parts.


The act of removing an AEG’s gears, springs and piston and replacing it with an HPA engine like the INFERNO Gen 2.

Contact Yoke

The connector on the MTW upper receiver that makes contact with the springs on the trigger board and delivers voltage between the two. More info:



When referring to an HPA engine, the front-most part of the engine that contains the moving components and nozzle. See the owner’s manual for each engine for more information:

DMR Mode

Designated Marksman Rifle Mode – A feature of the FCU that simulates the time it takes to operate the bolt of a bolt action rifle by disabling firing for 2 seconds after each shot. See the owner’s manual for your FCU for more information:


A feature of the FCU which controls the amount of time the solenoid remains open on an airsoft rifle. Measured in milliseconds. (1/1,000 second). See the owner’s manual for your FCU for more information:


Empty Magazine Detection – The technology in which an arm on a magazine makes contact with a switch on the control board when the magazine is empty. Depending on the MTW‘s EMD settings, this may require the bolt catch to be pressed again after a new magazine is inserted to resume firing, simulating a real M4. More info:


When referring to an HPA engine, an engine that requires a battery to operate but not an FCU, such as the BOLT. More info:

Expansion Chamber

The component of the WRAITH X that allows liquid CO2 to decompress into a gas after exiting the cartridge before entering the regulator and engine. More info:


Feed Tube

The part of an airsoft gun that connects the magazine to the hop and allows BBs to pass through. MTW‘s have used several types of feed tubes including the standard Feed Tube, Advanced Feed Tube, and the CNC feed tube available on third generation MTWs. These parts are not interchangeable.

MTW Billet Series Gen 3

Flex Line

An airline used to connect your HPA regulator to the grip line on your HPA gun. More info:


Firing Control Unit – The electronic board that operates an airsoft replica and allows you to adjust settings like the firing mode, rate of fire and dwell. More info:


Filtered Grip Line – A grip line released by Wolverine Airsoft in 2016 with a built-in, replaceable filter. It has been discontinued and replaced with the Grip Line with Integrated Filter, which has a smaller profile and non-replaceable filter, and comes standard with every HPA engine and MTW.


In AR-15 manufacturing, a forging is a block of aluminum that is heated and hammered into the shape of a receiver. The MTW Forged Series as well as Daniel Defense MTW MK-18 are both built AR forgings that are then milled to the MTW-Spec.


Feet Per Second – The speed at which a BB travels through the air, measured with a chronograph.


An enclosure in AEG which contains the gears, spring and piston. Gearboxes come in several varieties such as V2 and V3, for which specific HPA conversion kits are available. For example, the INFERNO Gen 2 V2 Kit can convert M4 style AEGs that use a V2 Gearbox.

Grip Line

The airline that extends from your HPA engine to the exterior of an HPA gun for which to connect a flex line and regulator. More info:

Hardpoint Adapter

An MTW-specific component of a WRAITH system that fits into the upper receiver and allows an airtight but easily separable connection between the engine in the upper receiver and an air stock in the lower receiver. The MTW and MTW-308 use two different versions. More info:



The component of an airsoft replica that applies backspin and “hop” to the BB before it enters the barrel, giving it more range. More info:


A Wolverine Airsoft engine specifically designed for AEG to HPA conversions that require an offset nozzle. More info:


High Pressure Air – Can refers to the technology of using air to operate an airsoft replica as opposed to the gears, springs and motor of an AEG. All Wolverine Airsoft are designed specifically for HPA technology.


The family of airsoft engines developed by Wolverine Airsoft including the INFERNO and INFERNO Gen 2 developed for AEG conversions and then later built into the MTW platform. More info:

Input Pressure

The air pressure coming out of the regulator into an HPA engine. Engines have minimum and maximum input pressure ranges required to function correctly such as the INFERNO Gen 2 with a range of 60-140PSI.


The manufacturing arm of Wolverine Airsoft, located in Kingsport, TN, specializing in CNC machining many parts of the MTW, HPA engines, regulators and more. More info:


The measurement of a BBs kinetic energy after being fired as measured by a chronograph. More info:

Joule Creep

The phenomena of using a higher BB weight than was used to chrono with, resulting in a higher joule measurement. More info:

JST Connector

The electrical connectors typically found on airsoft electronics and compatible LIPO batteries.


Lithium Polymer battery – a rechargeable battery used to power most airsoft engines and electronics. Wolverine Airsoft recommends a LiPo battery with a range between 6v and 8v for its engines.


In airsoft, a silicone-based lubricant like TechT Gun Sav.


When referring to HPA engines, an engine that works directly from contact with the trigger and requires no electrical components. Mechanical engines are named with a following “M” to differentiate them from their electrotechnical versions. Example: BOLT vs BOLT M and REAPER vs REAPER M.


Modular Lock – A firearm rail interface system developed and patented by Magpul Industries. As seen on many rails like the Invictus MK-1 and Invictus M-Lok Advanced Series Rail.


Modular Training Weapon, the Wolverine Airsoft family of purpose-built, HPA airsoft guns. More info:


A standard of parts designed to be compatible with the MTW platform. More info:


The front-most part of an HPA engine that makes contact with the BB and delivers air during firing. Different airsoft replicas will require different lengths of nozzles for proper firing. More info:


Offset Nozzle

An HPA engine design where the nozzle is vertically offset to fit into specific AEGs like the M14 and P90. Wolverine Airsoft developed the first out-of-the-box drop-in HPA engine for guns with offset nozzles, the HYDRA. More info:

Open Bolt

In HPA engines, a system where the nozzle rests in the back position and fires the BB through the hop, as opposed to a system where the nozzle rests in the forward position with a BB loaded in the hop.

Over hop

Applying too much hop to a BB when fired, causing the BBs to curve upward.


The internal moving part of an HPA regulator that opens and closes to allow airflow. For more information, see the owner’s manual for your regulator:


Puncture Pin

The component of a WRAITH system that punctures a CO2 cartridge once it is tightened. On WRAITH legacy products, the puncture pin adjustable. On the WRAITH X, the puncture pin is fixed. See the owner’s manual for your system for more information:

Real Steel

In airsoft, refers to real gun parts or accessories that are compatible with a platform like the MTW. (It does not mean it’s made from steel). More info:


The Wolverine Airsoft family of HPA engines designed to adapts our BOLT technology for M4 AEGs and MTW. Includes the REAPER and REAPER M.


A device that attaches to an HPA tank or other air source and reduces the pressure so that it can be used with an airsoft gun. Wolverine Airsoft developed the first HPA-dedicated airsoft on tank regulator, the STORM, which was followed up by the STORM Category 5. This regulator is also built into the WRAITH X system.


Rate of Fire – The speed at which an airsoft engine fires when in full-auto, measured in RPS (Rounds Per Second). This is an adjustable setting within the FCU.

Selector Plate

The mechanical part of an AEG that is controlled by the gun’s selector arm to slide back and forth to activate a switch on the trigger board, letting the FCU know whether to fire in semi or full-auto modes. More info:


(Single Moving Part) Wolverine Airsoft’s first HPA engine, released in 2014. It was replaced by the INFERNO.


The part of the HPA engine that receives electrical current to open and close a valve, releasing air into the rest of the engine. Wolverine Airsoft engines contain 2-way (INFERNO, HYDRA) or 3-way (BOLT, REAPER) solenoids. More info:



The Spartan Electronics family of control board is a trigger board and FCU all-in-one that allows you to program settings using the trigger. There are versions for AEG and MTW. More info:


The phenomena of sealing surfaces sticking to one another, for example rubber seats in a regulator. Wolverine Airsoft FCU‘s contained an anti-stiction algorithm that automatically makes small adjustments to dwell over time while the gun is at rest to help prevent stiction. More info:


The Wolverine Airsoft family of regulators, including the STORM on Tank (Legacy), STORM High-pressure (Legacy), Storm in Grip (Legacy), and STORM Category 5. More info:

Tight Bore Barrel

An inner barrel with a diameter of 6.03mm as used in the MTW.

Trigger Board

An electronic board installed in an airsoft gun that detects a trigger press (typically with a button) and sends a signal to the engine. Typically, has connects for an engine, FCU, and battery. More info:

Under hop

Applying too little hop to a BB when fired, causing the BBs to curve downward.


The component in the solenoid that opens and closes, allowing air to enter the engine. Sometimes is used shorthand to refer to the solenoid itself.

Valve Housing

The back portion of the engine that receives the solenoid and allows air to flow into the cylinder. See the owner’s manual for each engine for more information:


V2 Gearbox

The most common AEG gearbox type used in common M4 platforms replicas. Wolverine Airsoft makes drop-in kits for V2 gearboxes that can use either the Spartan Electronics or Gen 2 Premium FCU. More info:

V3 Gearbox

The most common AEG gearbox type used in common AK platform replicas. Due to the more restricted space for a trigger board, Wolverine Airsoft drop-in kits for V3 gearboxes use the separate Gen 2 Premium FCU. More info:

Wide Bore Barrel

An inner barrel with a diameter of 6.23. MTW’s use a tight bore barrel with a diameter of 6.03. More info:


The Wolverine Airsoft family of on-board air supply solutions that let you run HPA or CO2 on your MTW or AEG without an airline. Including the WRAITH CO2 Stock (Legacy), WRAITH CO2 Adapter (Legacy), and WRAITH X. More info:

Wolverine Airsoft 12 Month Limited Warranty

Your Wolverine Airsoft Product carries a 12-month limited warranty which covers all defects in manufacturing and material for the first 12 months from the date of purchase. Wolverine Airsoft will repair or replace any defective parts at their discretion.

This warranty is non-transferrable.

This warranty does not cover damage due to misuse/abuse of the system, improper installation, or operating the Wolverine Airsoft Product outside of the manufacturer’s specified operating range.

Not covered by this warranty are:

  • Battery
  • Normal component wear and tear
  • Acts of God
  • Component modifications not performed by Wolverine Airsoft

Warranty claims should be brought in writing to Wolverine Airsoft, LLC here.  

It is the responsibility of the customer to ship the unit to Wolverine Airsoft at the customer’s expense for warranty repair/replacement. Return shipping to the customer will be provided by Wolverine Airsoft, LLC (WA) via United States Postal System (USPS) or other courier at WA’s discretion. Standard for warranty return shipments is generally 2-4 business days for domestic (USA) and up to 15 days for international shipments depending on your country’s customs agency.

International customers may be directed to ship their units to an authorized service center within their country or region instead of shipping to our facilities in the USA. 

International customers are responsible for paying any applicable shipping duties or fees to and from Wolverine Airsoft service centers.

Tournament Locks

All Wolverine Airsoft systems can be controlled with a simple regulator tournament lock. There are many models of regulators on the market using different styles of tournament locks, but virtually all of them have an easy locking solution. If you have questions regarding safe tournament locking practices, please contact and we will assist you. 


The introduction of high-performance HPA technology has changed the airsoft arena. With the advantage of easy tuning and changes to velocity comes challenges for field owners to effectively regulate safe velocities. Open communication between fields, retailers, and coordinators and the HPA manufacturers is critical to ensuring a safe, fun experience for everyone. Being fully aware of the concerns and challenges that HPA technology presents to field owners, we have designed our products to be as safe and easy to regulate as possible. We are constantly seeking the input of retailers and field owners to help us find solutions for those concerns.

To our users

As an HPA user, you must recognize that your system is capable of seriously injuring other players if not used responsibly. We ask that you treat the technology and other players with respect. While we have created the system to make it as difficult to abuse as possible, we recognize that it can still be done. We rely on YOU to show honor and respect to other players on the field and help keep the hobby alive and well!

To retailers and field owners

As with any system, HPA or AEG, there will always be players who will find a way around rules and regulations. But, we want to do everything we can to address your concerns and make it as difficult as possible to abuse, and as easy as possible for fields to enforce their limits on our system. Please contact us at any time to provide input. Help us create an HPA product with outstanding performance that you can feel comfortable allowing onto your field.


All of the nozzles sold with the Wolverine SMP vary in length to accommodate various platforms but are identical in diameter so that internal adjustments cannot be made. This allows field owners to visually inspect the external system and not worry about internal adjustments.