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SP-8
By Bill Mills - Photos by Dawn Mills - Apr 2006

Overview

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

The first person we saw at the 2005 PSP Paintball World Cup was Bill Gardner, Jr. from Smart Parts.  We ran into Bill before even getting out of the parking lot, and when he saw us his face lit up like a child excited about a Daisy Red Rider 200 shot repeater range model air rifle under the Christmas tree. 

“Did you see it yet?” he asked.  Without having to define “it,” I knew he was talking about the SP-8, because it was such a departure from Smart Parts' existing stable of products.  While based on the Ion’s technology, the SP-8 is built and intended for the recreational and scenario paintball market, rather than the concept field tournament player.  Not only is the look different from what speedball players are used to, but the performance is not what scenario and woods players are used to.  The XP-8 is the first mass produced electropneumatic paintgun built specifically for the woods/scenario paintball, bringing an electronic trigger, and the functionality of multiple modes of fire and anti-chop eyes with it.

The SP-8’s exterior mimics the shape and feel of an XM-8 Battle Rifle, a prototype assault rifle designed by German arms manufacturer Heckler & Koch as a replacement for the US Military’s nearly 40 year old M-16 design (For more on the XM-8 see this link.)  While the real XM-8 has not yet been put into field service with the US Military, the SP-8 is available now.

Functionally, the SP-8 is basically an ion in a new body cover, much as its colored body covers can be replaced, the clamshell body of the SP-8 fits over a metal receiver that is the equivalent of the Ion's, and mates to a more complex grip frame.

Like the real XM-8, the SP-8 is built modularly.  The central component is the receiver and the grip frame.  A butt plate on the back of the receiver is locked in place with a push-pin, and can be quickly exchanged for an optional adjustable stock.  Similarly the foregrip, which locks into the carry handle on top and acts as a shroud for the barrel, is also locked in place by a push pin, and can be exchanged for a longer version.  The standard foregrip is short, and mimicks the XM-8’s Compact Carbine configuration.

At the top of the SP-8 is a Picatiny style sight rail with an open center.  This slotted rail accepts sights and accessories set up for military or hunting use.  The XM-8 is actually designed to use sights that integrate into the body shape locking onto the rail – if and when some of these become available to the public they will likely be a perfect fit on the SP-8, but include a rather hefty price tag.

Beside the sight rail, on the right hand side is the SP-8’s feedneck, angled at 45 degrees from vertical.  The feedneck is a part that fits into the upper receiver body, and guides paint down to the breech of the aluminum receiver inside. 

For shooters who want to set up hopper left, a left-hand feed conversion would not be a difficult job for an airsmith, and something that could easily be done as a relatively home conversion.  This is because the feedneck is a part of the outer, upper receiver, and can mate to the SP-8’s body breech from either direction.

Moving forward along the top of the SP-8 one finds the carry handle, a piece which extends from the sight rail to a raised section of the foregrip.  Immediately below the carry handle is the charging handle.  On the XM-8, this handle is used to cock the mechanism and chamber the first round of a freshly loaded magazine. 

The SP-8 doesn’t need a charging handle because its electropneumatic valve system is self-cocking, however the SP-8’s charging handle is more than just decoration.  The handle is actually a clamp, which slides onto rails in the top of the receiver halves.  It serves to hold the to receiver halves together, and to cover their seam preventing the entry of dirt or rain.  A peg underneath the front of the handle keeps it locked in place until the foregrip is removed.

The foregrip itself is made of the same heavy duty polymer as the SP-8’s upper receiver, with the addition of a rubber-like grip surface wrapping around its bottom and up onto each side.  A series of engravings on the right and left mimic the shape of the foregrip vents on the XM-8. 

At either end of these cosmetic vents is a pair of screw holes, which allow for the mounting of accessory rails.  On the bottom of the foregrip, near its front are another pair of holes, these with threaded metal inserts inside.  The two bottom holes allow for the mounting of an additional reail, bipod, or other similar underbarrel mil-spec accessory.

Peeping out of the front of the foregrip is the SP-8’s barrel.  The stock barrel is fourteen inches in length, though it appears more compact when mostly hidden by the foregrip and body.  The actual breech of the SP-8 is about four inches deeper into the gun than that of the XM-8. 

Four rows of porting on the barrel line up with air space inside the foregrip helping to keep the SP-8 from being too loud.  Four slots are cut into the muzzle, and inch and three-quarters in length, mimicking the look of the XM-8’s muzzle. 

The SM-8 uses the same style of threading as the Smart-Parts Ion and Impulse, which means that most Ion/Impulse barrels will work with it, as long as they fit within the shroud. 

While it looked a bit odd to see the red All American style tip sticking out of the front of the foregrip, a Freak barrel system screwed easily into the SP-8.

Near the back of the foregrip, is a single aluminum push-pin which locks the foregrip in place.  An o-ring resting in a groove on the pin gives it friction to prevent it from falling loose. 

As it shipped stock the pin was in so securely that it needed to be pressed out with a narrow screwdriver.  Reinserting it could be done with finger pressure up to the last quarter inch.  A sharp tap with the SP-8’s magazine easily drove the pin the rest of the way into place.

The SP-8’s grip frame makes up the lower edge of the receiver and has a faux magazine in the front.  With a thumb-latch release the fake clip can be slid out of the grip frame revealing the vertical regulator that controls the SP-8’s velocity.  The regulator is angled forward at about 15 degrees, and can be used on field with or without the clip covering it.

The regulator screws into an ASA that is integral to the magazine receiver.  Sitting inside the ASA is a fine mesh filter, designed to protect the internal solenoid valve from debris.  Because a standard ASA fitting is used, a variety of aftermarket regulators is available as options for SP-8 owners. 

While many players will opt to use the SP-8 with compressed air, it can also be used with CO₂.  When CO₂ is used Smart Parts recommends that only an anti-siphon tank be used.  Vertical tank placement in a harness and use of a remote line can achieve the same effect, but the important factor is that only gaseous CO₂ be fed directly to the SP-8, not liquid.

Velocity adjustment is achieved by twisting the wrench flats at the bottom of the regulator.  On the right hand side of the grip frame is a compact low pressure gauge, like that found on the Ion, which can be used to monitor the pressure of gas fed to the solenoid valve and exhaust valve.

Not only does Smart Parts include hex wrenches with the SP-8, but an open end wrench as well, for velocity adjustment.   along with the tools and spare parts is a wider than usual barrel blocking bag, which fits over the muzzle of the SP-8, including the front edge of its foregrip - so even if a barrel shorter than the foregip is installed, it can still be covered.

Knowing the regulator’s output pressure is important, as levels above 200 psi can damage internal components and void the SP-8’s warranty. 

Unlike the real XM-8, the SP-8 features a blade style two-finger trigger in a thick trigger guard.  Two external adjustments are available on the stock trigger.  A screw accessed through a hole where the trigger guard meets the grip frame adjusts the forward travel limit of the trigger, while a screw in the trigger itself sets the rear travel limit. 

A magnetic attract style trigger return provides a trigger pull that is solid enough to avoid accidental discharge, but becomes lighter as the trigger is pulled further back. 

From the factory, the SP-8 reviewed had a trigger pull of 0.29 inches measured at the tip of the trigger.  Activation of the microswitch occurred approximately 0.17 inches into the pull.  The SP-8’s serial number is laser engraved on the bottom surface of the trigger guard. 

Inside the grip frame, the SP-8’s circuit board is programmed to provide four different modes of fire.  A true semi-automatic mode fires one shot per trigger pull.  Rebound modes add additional shots after a few shots have been fired at a minimum rate, providing an effect similar to the original Smart Parts Turbo mode.  The three shot burst mode fires a burst of three shots when the trigger is pulled, and full automatic fires repeatedly while the trigger is held down.  Since the ability to change modes requires tools to open the SP-8’s wraparound grips, the paintgun is locked on field into whichever mode it is set, making it legal to use on tournaments or fields which restrict play to semi-auto or ramping modes only.

The SP-8’s grip frame is a 45 style, like so many in paintball, and features a rubber-like wrap-around grip.  The grip covers not only the grip frame, but also the stock bottom-line style ASA fitting.  The result is that the grip frame looks more squared off around the bottom than a typical paintgun, and the bottom-line is more visually integrated into the grip.  A deep groove runs through the bottom of the grip, allowing the lower portion to be easily cut away for players that would prefer to add a drop forward, rail, or other form of air system mount that will not fit beneath the protective cover.

Just above the left side of the grip is another point of departure between the Ion grip frame and that of the SP-8.  One of the features of  the Ion is the paintgun’s “bubble” power switch.  The flexible bubble, when pressed inward, activates a button on the Ion’s circuit board.  Pressing with just enough pressure can be tricky, especially with gloves on.  The SP-8 design replaces the bubble with a clear hard plastic power button that activates the circuit board switch when pressed.  Protruding slightly from the side of the frame the new power button makes the SP-8 easier to turn on and off than the Ion.

The power switch is also used to activate or deactivate the SP-8’s break beam anti-chop “eye” system.  On either side of the breech, an infra-red emitter and detector are wired into the control circuitry so the SP-8 will wait until a paintball has fed before it fires, reducing the chance of chopped paintballs due to mis-feeds. 

Continue to How It Works

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