K-CQB
by Bill Mills - Photos by Dawn Mills - Aug 2007

Features HowItWorks Disassembly Testing Data

The K Series paintgun from Hummer, Ltd., is a modular .68 caliber paintgun built to adapt from roles as a true military and police simulation tool to a regular recreational paintball marker, or somewhere in between. Hummer Godforce Paintball (HGP) is a Taiwan based manufacturer that has been producing milsim markers since 1996, though they are mostly known in the states under the names of companies that import their markers. As these agreements are non-exclusive, you might find different configurations of HGP's products under various marker and brand names.

Many of HGP's earlier products utilized unusually small .43 caliber paintballs, in order to feed via expendable cardboard shells to simulate the magazine feed of an assault rifle. Their later T68 series markers moved up to .68 caliber with standard paintball hopper as feed mechanism, while maintaining a physical receiver shape close to that of an M-16 assault rifle.

The newer K-Series takes a slight step back from part for part realism, and as a result is less complex to produce, compatible with some off-the shelf paintball accessories from other manufacturers, and features a configurable feed system. The sample marker used for this review, an HGP K-CQB can switch from traditional hopper-right feed to spring fed interchangeable 16-round magazines in a matter of seconds.

The K-Series marker can operate either on CO2 or compressed air, and there are a wide variety of options as to how the gas supplies can be configured. Most set-ups involve feeding gas through a vertical ASA (Air System Adapter.) While the marker's magazine shroud gets in the way of screwing a CO2 tank straight into the ASA, the shroud can be removed, allowing a vertical on-gun bottle configuration, which uses gravity to eliminate liquid CO2 induced velocity spikes.

The marker's receiver is die cast in two pieces. Main assembly screws pass through the receiver into steel nuts with nylon locking inserts, making stripped screw holes in the receiver an impossibility. Unlike similarly styled receivers other manufacturers, the nuts are not embedded into the receiver, so a box-end wrench is included, as well as a straight slot screwdriver for maintenance. Each nut is also seated atop a short taper belleville washer and lock washer. During disassembly these seem to have a mind of their own, looking for a quick escape – however, in testing, the the nylon lock inserts in the nuts made these washers unnecessary.

The K-CQB included a male ASA fitting and quick disconnect already installed, for use with a remote hose and tank, and it was field tested in this arrangement. Additionally the optional bottom-line was used for test-stand firing.

The bottom-line ASA is shaped like that of the Tippmann A5, and secures with a single screw which passes from the left side of the grip to a nut in the right. The bottom-line was connected via steel braided hose to a male ASA, which had slightly thicker threads than the remote adapter, and took considerably more effort, and the use of a wrench to properly seat in the marker's central ASA port. Once it was in, it was airtight and worked without problem.

The bottom-line ASA places any tank screwed into it at a downward sloping angle. This is beneficial for two reasons. First, when using CO2, it will keep liquid CO2 away from the valve when the marker is held level, delivering better velocity stability, and it also allows the use of thicker compressed air cylinders, as the angle gives room for them to fit without interference from the collapsible stock.

Addditionally, a gas port on the right side of the marker allows a hardline connection to HGP's integrated gas stocks, which hide slender CO2 cartridges inside a telescoping stock.

The K-Series grip frame is molded polymer in three pieces – two main halves and a trigger guard, meaning a two-finger trigger and guard upgrade is a drop-in procedure and is Tippmann A-5 parts compatible. In fact, during testing for review, a Tippmann A-5 E-Grip bolted right on to the marker and worked when the K-Series safety was installed in place of the Tippmann safety.

An aluminum cross-block safety serves to block the K-Series trigger from moving in safe mode, or leave it free to swing in the fire mode, where a red o-ring shows that the marker is live. Because the K-Series receiver does not have walls extending into the grip frame like an A-5, the safety is secured by a C-Clip on its right hand side.

At the marker's rear is the 5-position AR-15 style telescoping stock that adjusts from 8 to 12 inches in length. Gripping the release on the bottom of the stock unlocks it to freely slide to a new position. The receiver's rear shape and screw positions also match those of a Tippmann A-5, providing compatability with existing aftermarket end-caps and stocks.

Moving to the top, one finds a Picatinny style sight rail running the length of the marker's receiver. Being a long accepted standard, there are a very wide variety of accessories, carry handles, sights and night vision scopes which will quickly and securely mount to this rail. Just below the rail is the marker's cocking handle. Because the K series are blowback powered semi-auto markers, they must have their hammer cocked, compressing their mainspring before their first shot is fired. The cocking handle is linked solidly to the hammer, and will be in the back position when the marker is cocked. It moves forward and back with the hammer when the marker is fired.

Accessory rails are not a shortcoming of this marker it is bristling with attachment points. In addition to the top rail, a 5-inch rail is mounted on the left side of the receiver, well placed for items like a tactical flashlight, a bottom mounted rail is available for use if the magazine feed is removed, and the barrel shroud carries another three, and the vertical foregrip which is mounted on the bottom shroud rail has yet another short rail on its side.

The breech is where one finds the most unique featureof this marker line. The K-Series breech may be fed either from the upper right, or from a spring fed detachable magazine, straight from underneath.

For use with a traditional hopper, a right side feedneck attaches to the receiver via a pair of screws, and a plug blocks the magazine feed port. A top feed port blocker goes in its place when only the magazine feed will be used. It should be noted that longer screws are used to mount the side feedneck than the upper feed port blocker.

The longer screws secure the magazine feed port plug in place so that it will not fall out during use. The shorter screws must be used with the upper feed port blocker, so they do not get in the way of paintballs feeding from the magazine. This information is not covered in the instruction manual.

The magazine feed is placed underneath the breech, and sized similar to that of an M-16 rifle, with a similarly operating magazine release button on the right hand side. Unlike an M-16, the K-Series has a gas port for its valve directly in front of the trigger guard, which locates the magazine release button about an inch too far forward to reach with the right index finger while holding the marker's grip. To adapt for this position, a magazine release extension is used. A pair of connected levers allow the user to easily reach the release, causing a magazine to drop out.

The K-Series spring loaded magazines comfortably hold 16-rounds (17 balls will actually squeeze in, and HGP calls it a 17-round magazine – but 16 seems to be a better fit.)

While 16 round magazines may seem rather limiting to the modern paintball player, police and military units which use paintball technology for force-on-force training, will find it to be a much closer simulation to the equipment they use in the field. Similarly the ammo limitations and magazine changes appeal to milsim paintball players that want to emulate similar tactics.

Spring feed magazines provide a number of challenges for marker and loader designers. While a few have appeared over the years such as the PS-15 and the MZ-16, the only to go into large scale production is the Q-Loader, which uses a shape and drive system that is far removed from that of an assault rifle magazine.

Two of the design hurdles facing many who have tried making compact spring fed magazines are the fragility and deformability of paintballs. Real bullets can handle a strong magazine spring as they have metal casings and can withstand a lot of pressure. Paintballs on the other hand can smash or break with too much pressure, and feed inconsistently, causing chops if there is not enough spring pressure. Additionally, the paintballs need to be kept in the magazine, until ready for feeding, or the spring will shoot them free when the magazine is being stored or handled.

The most common way spring fed systems have worked in paintguns is a simple straight magazine, with a spring and follower. As the magazine gets longer to accommodate larger numbers of paintballs the spring gets more compressed when it is full, resulting in more pressure applied to the paintballs. Adding to the design problems are the fact that with a detachable magazine, paintballs may be facing that spring pressure for an extended period of time before the actually being fed. If the paintballs deform and become oblong while the magazine is being carried in a vest ammo pouch on a hot day, they won't feed.

The K-Series magazine mimicks the general shape of a traditional rifle magazine, and is made of a translucent resin. Internally it has a U-shaped channel for holding 16 paintballs. Topping the magazine is its feed-port, which uses a spring loaded collet, and three ball bearings, much like a quick-disconnect fitting, to keep the paintballs in the magazine. The small ball bearings protrude into the feed path, blocking the balls from exiting, much like a ball detent would in a marker's breech if it could not retract. When the magazine is loaded into the marker, the collet is automatically depressed, allowing the ball bearings to retract under the force of a passing paintball.

In the K-Series magazine, a long, and soft spring presses against a spherical follower, and that is what drives the paintballs from the magazine into the breech. A unique mechanism ensures that the paintballs only face spring pressure once the magazine has been loaded, reducing the risk of ball deformation. A thin cable is attached to the magazine follower, leading through the magazine path to a ratcheted crank. The first step in loading the magazine is to turn the crank, which retracts the follower. Paintballs are then loaded while the feed gate collet is held open.

Spring pressure is not applied to the paintballs until the magazine is loaded into the marker, which activates a release latch for the ratchet at the same time it opens the feed gate, putting a paintball in the breech. Three ball-bearings in the collet prevent a paintball from rolling out of a loaded magazine until it is locked into the marker.

The magazine's follower mates up to the bottom of the breech when the magazine is empty. Every paintball loaded into the magazine gets fired, there are no “buffer” rounds.

The entire magazine feed system is a bolt on accessory, like many of the K-series components, making for a very modular system – some US importers sell K-series markers configured only for hopper feed.

The CQB's Rail Integration System (RIS) style barrel shroud, which mounts firmly to a block in the front of the receiver which also contains the Spyder style barrel threads. The block front end is another modular feature, allowing a change of barrel thread types to be made as easily as changing a component.

The sides of the barrel shroud are equipped with 4-inch long Picatinny rails, while another rail on the bottom is 6 inches in length. A foregrip with quick-locking thumb screw was included, also featuring a very short 1.5-inch Picatinny rail on its side.

The barrel is 11 inches in length, of a smoothbore design, with 6 rows of porting over its last 3 inches. Threads on the muzzle allow the mounting of optional muzzle-brake/suppressor accessories.

The suppressor which HGP produces and designed for use on the K-CQB was not reviewed, as at the time of writing, its design had not yet undergone BATF review (US law does not offer a clear definition of firearm supressor, instead giving the BATF technical branch the responsibility of reviewing suppressor-like devices – even if not designed for use on firearms – to determine if they are indeed considered firearm suppressors, and subject to federal regulation.)

The K-Series manual consists of a pair of single sided 11-3/4”x16-1/4” single sided photocopied sheets of paper. One sheet bears an exploded parts diagram with parts labels and all o-ring sizes, and operational warnings, while the other is a photo illustrated loading and cleaning guide. While the manual does not go into great detail, and its translation to English may not be perfect in places, it is enough to guide someone who has some experience repairing and maintaining blowback markers.

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