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98 Custom - 2006
By Bill Mills - Photos By Dawn Mills - July 2006

Overview - How It Works - Disassembly - Testing - Raw Test Data

OVERVIEW

Tippmann’s 98s are paintguns with a serious pedigree.  Twenty years ago Dennis Tippmann Sr., had been in the business of manufacturing miniature replica working machineguns (.22 cal replicas of .50 cal machineguns.)  Then he turned his attention in a new direction – paintball. 

The Tippmann SMG-60 was a head-turner.  At a time when Constant Air (refillable CO₂ tanks instead of 12 gram cartridges) was a custom built air-smith add-on, and pump or bolt action paintguns were the only option, the SMG-60 offered the ability to fire in select fire full-automatic, and was powered by a refillable CO₂ tank that screwed into the back like a stock.  The SMG’s .62 caliber paintballs, and 15 round spring fed magazine were limiting factors, but that didn’t stop it from becoming popular, or from most paintball fields banning full-autos and requiring SMG owners to install lockout screws to be field legal in semi-auto.

The SMG-60 was followed by the SMG-68, a nearly identical paintgun that accepted the now standard 68 caliber paintballs, and shipped as a semi-automatic.  Then came the 68-special, using a nearly identical receiver, but abandoning the clip for the more popular feedneck and hopper configuration.

After the Special, came the Pro-Am, the Pro-Lite, Mini-Lite, the SL series pumps and the Carbine and F/A.  All the while Tippmann kept up a reputation for extreme durability and responsive customer service.  Then with the 1998 model year came a Paintgun from Tippmann that worked on the same principles, but also made some significant design departures from previous Tippies.  The Tippmann Model 98 utilized a die-cast clamshell receiver which lowered its price tag while still maintaining durability, and its new trigger group offered a crisper, lighter trigger compared to the heavy machinegun feel of the earlier Tippmanns. 

The Tippmann Model 98 was a runaway success.  With mass merchant sporting goods store distribution, and as the standard rental model at a large number of paintball fields, the 98 has introduced untold numbers of players to the sport of paintball in the last eight years.  Following the release of the Model 98 came the 98 Custom which is essentially a Model 98 that is built to be more easily upgraded.  While the A5 has also hit dealer shelves, the 98s have had tremendous staying power, available for several years with only very minor design changes.

We took a look one of the latest versions of the 98, a 98 Custom upgraded with the new Equalizer board.  This 98 Custom included two of Tippmann’s most significant features introduced in 2006 – their new mechanical based Anti Chop Technology, and their licensing and production of Wicked Air Sports’ Equalizer boards.  While the electronic trigger system is an upgrade, the ACT bolt is a standard feature for the 98 Custom Basic.

Tippmann’s Anti Chop Technology, or ACT utilizes a similar concept to the spring loaded anti-chop bolts offered as aftermarket upgrades for a number of stacked tube paintguns, but is built to work with the 98’s inline valve, and breech arrangement.  In standard Model 98, the breech, valve and hammer are all in a single line.  A link rod sits above the valve and links the hammer (which Tippmann calls a Rear Bolt) to the bolt.  When the mainspring throws the hammer forward, the bolt is pushed closed, the hammer hits the valve releasing propellant gas, and a small amount of gas is vented from the back of the valve, pushing the hammer back, opening the breech at the same time.

With the ACT system installed, the link rod is not fixed to the hammer.  Instead it has its own spring set.  When the hammer comes back, it pulls the link rod back, opening the breech.  When the hammer is driven forward during firing however, it is the ACT spring that causes the bolt to close in a separate action for the first part of its stroke.  Since the force needed to close the bolt is much less than the force needed to strike the valve, this means that the bolt can moved forward be a relatively soft spring – so soft in fact that it won’t break or chop a paintball in half if it is only part way into the breech.

However, just the ACT spring pressure alone could potentially cause blowback problems, with the burst of gas that propels the paintball blowing the bolt open at the moment of firing.  To combat this, the ACT system uses a very simply locking system. 

When the bolt and hammer have moved about halfway through their forward stroke, if the bolt has not encountered an obstruction, the link arm locks into the hammer.  Now, when the bolt completes its forward stroke it has the force and inertia of the ACT spring, the mainspring and the hammer behind it, preventing it from blowing open during firing.  This locking action sets the ACT apart from other spring-loaded anti-chop bolts.

The locking is achieved with a small offset bend in the link arm that passes through a pair of steel pins going between the two 98 body halves.  When the bend in the link arm moves past the pins, the arm is pushed downward, forced into a hole in the hammer, locking the two parts together.

The ACT has necessitated a few changes in the design of the 98 Custom.  It is not marketed as a retrofit or upgrade for older model 98s, because a larger space is required for the link arm, with room for it to move vertically, and for the pins that engage its locking mechanism.  To upgrade an older 98 or A5 to use ACT would require replacing the body, as well as adding the ACT parts.  Additionally the back plug has a new near its top, to act as a seat for the ACT spring.  It is important for owners of ACT equipped 98s to consider this with any accessory that mounts in place of the rear plug.  Rear velocity adjusters, rear mounting stocks, and similar accessories must have a second spring hole in order to be compatible.  All of Tippmann’s newer rear mount accessories have this ACT spring hole, but some dealers may have older units in stock.  While this review was being written one customer caught in the transition, with an older stock and a new 98 with ACT was advised to contact Tippmann tech support to get their stock upgraded.

On the outside, the 98 Custom looked much the same as earlier 98s.  Its die cast aluminum body had a less glossy finish, a recent change in the type of power coating process Tippmann uses to coat the receivers.  As the aluminum alloys used for die-casting do not take anodizing consistently, paint and baked electrostatic powder coating are common options for protecting it.  Early Model 98s used a painted finished, which could sometimes bubble or peel if paintball fill was left on it for long periods of time.  Tippmann switched to a poly based powder coating having greater durability.  According to Tippmann’s tech department the latest change in powder coating provides an even more durable finish. 

The two clamshell halves of the receiver are held together by screws which fit into nuts seated in the opposite half.  This arrangement protects against the possibility of stripped threads ruining a receiver. 

The 98 design continues to use Model 98 threads for barrel attachment.  These very coarse threads are thick enough that they can be cast reliably into the two receiver halves.  In 2003, the Model 98 barrel thread specification thread was changed slightly in order to provide better barrel alignment.  This can sometimes cause confusion as the old and new 98 thread standards were not given officially different names by Tippmann.  Some barrel manufacturers cope with the difference by producing barrels with one thread set, and fitting them with a short adapter to the other.  Noting the year of manufacture can be important for a player buying used 98s or barrels, and planning to mix or match them.

The stock barrel included with the 98 custom is eight and a half inches from breech to muzzle.  Its smoothbore interior runs uninterrupted for the first 4 and a half inches, where there is a ring of 12 ports that are 0.125-inches in diameter.  The muzzle is thicker than the rest of the barrel, over a length of about an inch and a half, where six rows of additional ports serve to dissipate gas.

Above the breech is the Tippmann feedneck.  It’s unique design allows it to swing down and to the right when the front sight is pressed, to unlock it.  This provides easy breech access for cleaning.  Once opened, the feedneck can simply slide backwards for removal allowing detailed cleaning.

Moving further back along the top one finds the dual sight rail, which allows the 98 to use either 3/8 inch or Weaver rail compatible sights.  The offset placement of the feedneck, rather than a center-feed provides direct line of sight for most low profile optics.  At the back of the rail is the built in rear sight.  The front sight blade, located just forward of the breech on the receiver does double duty as the spring loaded release latch for the feedneck.

The rear sight is adjustable for elevation.  Early Model 98s included screw adjustment for windage (left to right adjustment) but this feature was so little used by their customers that it was removed from the design, making assembly and disassembly of the two clamshell halves easier.

At the back of the 98 Custom receiver is the back plug, now bearing the ACT logo, indicating that Anti Chop Technology is installed.  Split wraparound grips are installed on the grip frame, which is a part of the receiver.  Because they are split in half, rather than a single piece, they do not need to be removed for the receiver to be disassembled.

At the bottom of the grip is the stock ASA – Air System Adapter – held in place by a pair of industry standard 10-32 screws threaded into a pair of square nuts that fit into recesses inside the receiver halves.  The ASA is angled slightly, rather than being a true horizontal bottom-line style.  As long as the 98 Custom is being fired from a horizontal, or up-ward position, the angle of the tank placement serves as an effective block to minimize the chance of liquid CO₂ being fed to the marker’s valve.

The trigger guard of the 98 Custom is a piece that sets it apart from the Model 98.  Rather than being a part of one of the receiver halves, it is a separate piece.  This allows it to easily be exchanged for a two-finger trigger guard.  Internally, the particular 98 Custom reviewed was equipped with a WAS Equalizer E-Trigger.  While not included with all 98, the E-Trigger is an optional Tippmann Accessory.  In early 2006, Tippmann licensed the WAS board technology from Wicked Air Sports, adopting it as the new standard electronics package available for both the 98 Custom and the A5. 

Forward, along the bottom of the 98 Custom lay the foregrip.  The upper portion of the grip is integrated into the receiver, while the lower half is made of molded plastic with smooth finger grooves in its front.  The lower half of the foregrip can be optionally removed and replaced with a vertical ASA to allow use of an expansion chamber or vertical bottle placement.
 

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