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Building an ULE Automag
by Bill Mills

Through the years, Airgun Designs has been developing new products, and improving on their previous models.  As with most paintgun manufacturers they have often simply released new paintguns as new features come out, until some of their more recent products, which have been mainly available as upgrades.  Several components, like their new Y frame and ULE bodies are not available in off-the shelf models.  For players who already own Automags, many of these components are designed as upgrades.  Now, there are enough of these upgrade components that a player can custom build an Automag with the parts that they want, rather go through the expense of buying a full paintgun and replacing stock components with upgrades.

This two article series looks at several of AGD’s latest Automag components and builds them into a light-weight, high performance paintgun.

The starting point for this paintgun is the body rail and sear pivot, as well as a couple of grip frame screws.  These parts are the only “stock” Automag parts, and are all that would be left of the original Automag if this project were an upgrade.  The body rail is the piece that goes between the body and the grip frame.  A year ago, Extreme Rage made an Omega body rail that was milled out to be extra light and would have been ideal for this paintgun, unfortunately, it was a short lived product, so a stock rail was used.

An Automag sear and sear pivot were dropped into the body rail.  The sear is the heart of the Automag.  When the trigger rod (the pivoting rod attached to the bottom of the sear) is pulled the sear rocks forward releasing the Automag’s bolt, and shutting off the flow of gas to the gun’s air chamber.  This allows a fixed volume of gas to be used to fire a paintball out of the barrel.

The body chosen for this Automag was an Airgun Designs ULE, or Ultra Light Engineering body.  Until the relatively recent import of milled aluminum bodies from AGD UK, all of AGD’s Automags featured steel body tube construction.  A single tube held the barrel and valve components in place.  The Automag’s twist lock barrel system set the minimum size for a ‘mag body.  While the original Automag twist lock barrel system changing barrels fast for cleaning was easy.  However, in recent years, as Airgun Designs worked on refining their valve and bolt designs for better efficiency, they discovered a problem with the twist lock barrel system.  The breech for the paintgun is a part of the barrel, and when players used aftermarket barrels, they would be inserting a breech of a different diameter into the paintgun.  This made matching the bolt diameter to the breech next to impossible.  The solution to this was to switch to new bodies in which the breech was a part of the receiver rather than the barrel.  All of Airgun Designs’ aluminum bodies do this, and utilize Autococker style barrel threading for compatibility with a host of aftermarket barrels.

The ULE body is compact and lightweight, weighing in at just under 4 ounces.  It has a lowrise feed neck that is attached with Angel style feedneck threads, allowing the use of aftermarket locking feed necks.  Also Angel threaded is the ball bearing style ball detent which can be replaced with any number of aftermarket detents.  Minor cosmetic milling on the front of the body, and an angled front-end style it to look like a little more than a colored aluminum pipe. 

Because the body rail was designed for the Automag, Minimag or Automag Classic, it has a barrel detent pin installed in order to lock a barrel in place.  This is not used with the ULE body and must be removed.  Pulling it out was a matter of pressing the bottom of the pin into the rail by squeezing the whole assembly in a vise, and then using a pair of pliers to wiggle it the rest of the way out.

Completing the body of the ULE Mag is a Y grip.  In the late 1990s, Airgun Designs released the Z grip for the Automag.  The Z grip was angled at nearly 45 degrees backward.  While this was impractical to hold in a shoot from the hip position, it was in the right position for a player to hold while tucked into a bunker with the air tank of their paintgun up to their shoulder.  The Z grip was not popular in its initial release, but in recent years there has been renewed interest among Mag owners online, and WDP as well as aftermarket grip manufacturers have begun producing 90 degree grips with lobed back edges which work on the same principle.  The Y grip is a re-design of the original Z grip, though the angle of the grip frame is reduced, making it more comfortable to shoot from different positions.  Internally the Y grip, like AGD’s Intelliframe has mount screws to allow a switch to be installed for on demand electronic loader activation. 

The Y grip trigger is the same two-finger trigger found on the Intelliframe.  It is a blade style trigger with a finger shaped curve at the bottom.  This design naturally cradles a player’s typical finger placement.  A pair of Hogue Colt 1911 grip panels are included, but installed backwards to fit the Y frame’s reverse angle.

Installing the grip frame to the body and rail consists of guiding the sear’s trigger rod into place in the grip frame, setting the ULE body on the body rail, and then installing the front grip frame screw to hold the entire assembly together.  At that point it looks like a paintgun, and is ready to have the valve assembly dropped in.

The original Automag AIR (Air Integrated Regulator) valve, often called the Classic, was found in the Automag, the Minimag, and the more recent Automag Classic.  As an assembly, it consists of the regulator in the rear (the Automag was the first production paintgun to use a regulated gas supply,) an on/off valve, an air chamber, and the bolt.  The Automag design was unique among paintguns up until the late 1990s, as it lacked a hammer.  Instead of using a hammer to strike a valve, the Automag charges a fixed volume air chamber with regulated gas, and then using that gas to both close the breech by sliding the bolt forward, and to fire the paintball. 

The Automag system provides consistent velocity using a fixed pressure and volume of gas used to fire the ball.  Once the air goes past the regulator, it flows through the ‘Mag’s on/off valve and fills the air chamber.  When the trigger is pulled, the sear performs two tasks.  It releases the bolt while simultaneously closing the on/off valve.  The gas pressure inside the air chamber pushes the bolt forward, and when the bolt reaches the front end of it’s stroke that air is allowed to flow through the bolt, into the breech and out of the barrel.  The on/off valve being closed prevents new gas from flowing into the air chamber from the regulator.  When the gas pressure in the air chamber is exhausted, the mainspring pushes the bolt back to its starting position.  When the trigger is released, the sear once again latches onto the bolt, and allows the on/off valve to open, refilling the air chamber with gas from the regulator, ready for the next shot.

The original Automag valve assembly was made of stainless steel, for extreme durability and corrosion resistance.  The original valve was followed by the Automag RT valve, a compressed air only version with a faster recharge rate.  While the RT valve was technically superior, it was only compatible with the Automag RT paintgun, because it used a unique “banjo bolt” that delivered air to the valve through the rear grip frame screw rather than an external hose.  The RT valve was followed by the ReTro Valve, which was basically the RT valve in a new package, it was styled to fit the original Automag bodies, giving older ‘Mag owners an upgrade path, and giving more modularity and interchangeability to newer Automags like the E-Mag and RT Pro. 

The most recent valve in the Airgun design line is the X-Valve, and it incorporates two major design changes.  The first change is in materials.  The X Valve is made primarily of aluminum, with some stainless steel and brass components.  The change in main materials came about from AirGun Designs realizing that tournament level paintball players were more interested in a lightweight, fast operating paintgun than a paintgun that will last through more than a decade of use.  While the hard anodized aluminum valve body is very durable, and is considered industry standard in paintball, it will wear faster than its stainless steel counterparts.  The change in materials allowed for not only the look of a hard ano finish, but also meant a 3 ounce reduction in weight for the valve assembly.

The other design change incorporated into the X Valve is more significant to the modern Automag – the Level 10 bolt.  AirGun Designs has long fought a reputation that its paintguns were “ball choppers.”  The blow-forward bolt system found in the Automags was never gentle on the ball.  If a player shot faster than paint could feed, a partially fed paintball was sure to be chopped by the force of the closing bolt.  AGD first combated this with their powerfeed, to help prevent paintballs from bobbling back up the feed tube when hit with blowback gas.  The company later combated ball chopping by again focusing on feeding issues with the Warp Feed.  The theory again was to focus on preventing ball chop by getting paintballs into the breech fast enough.  While the powerfeed helped, it was later outpaced by increasing rates of fire.  The Warp Feed was a sound solution.  While it also gave players the advantage of a decreased target profile, it added weight to the paintgun, and was different enough that few upper level tournament paintball players used it.  Mainstream tournament paintball was heading towards smaller, more compact paintguns with short, vertical feed necks. 

Enter Level 10, also known as Super Bolt – II.  AGD experimented with the Super Bolt, releasing it to beta-testers and sponsored players.  It had a Delrin sheath, and stainless steel core, but was a fraction of the weight of the original Automag bolt.  The light weight meant less moving mass in the Mag, and thus less recoil when firing.  The Delrin sleeve proved problematic, but the lessons learned with the Super Bolt went into Level-10.

The Level – 10 incorporates a lighter weight, thinner walled stainless steel bolt with a new pressure based anti-chop system.  While other manufacturers have concentrated mainly on infrared or impact based feedback electronics to prevent their paintguns from chopping a partially fed paintball (and so has AGD with their X-Mag electronic paintgun) Level – 10 approaches the problem from a pneumatic perspective.  Internally the Level – 10 bolt has a two stage core.  Like the original Automag bolt, this core acts as a piston, driving the bolt forward under gas pressure.  By changing the diameter of the piston, and adding a vent hole, the bolts closing pressure is reduced to the point that AGD President Tom Kaye has performed public demonstrations where the bolt was stopped by his tongue without injury.  While the bolt still moves quickly, it does not chop a partially fed paintball, but rather bumps into, it and resets.

Continue to Part 2

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