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Impelling Force

Smart Parts’ new Impulse electropneumatic semi-auto

© Ravi Chopra, 2000

Smart Parts set a new standard in design originality way back when they first released the Shocker paintball gun. The Shocker was unique in a number of ways. First, and most notably, it had an electric trigger - the first electropenumatic paintgun. Furthermore, it has a completely unique cycling system, unlike the electros that followed it to market, most of which borrow significant aspects of their operation from blowbacks, blowforwards, and auto-pumpers. Hampered now only by notorious inefficiency, the Shocker remains today one of the most unique and innovative paintguns available.

So why am I talking about the Shocker, here on the eve of my introduction of Smart Parts’ new electropneumatic, the Impulse? It’s because this new ’gun is very nearly the exact opposite of the Shocker in all those respects.


The first question I like to ask is, "how does it work?" In answering this question we come to the first major differences between the old and the new. Where the Shocker introduced a completely new way to cycle and deliver gas (for a paintgun), the Impulse is decidedly derivative. If you’ve read my articles on the Angel or Bushmaster 2000, you don’t need to read much further. The Impulse uses the same basic electropneumatic system with one little twist to keep things interesting.

For those who are not familiar with how these other electropneumatics work, here’s a brief description. The Impulse fires from an open bolt. When you pull the trigger, it activates a microswitch in the grip frame. This signals the initiation of a sequence of events programmed into the circuit board in the grip frame.

When the cycle sequence is initiated with a trigger pull, a solenoid-driven valve (essentially an electronically switched 4-way) switches the air-flow to a sort of ram, not entirely unlike that on the Autococker. The difference is that the ram works in the opposite direction. Rather than cycling back and forth, it starts back and cycles forward and backward when the Impulse is fired. When it goes forward, it pushes the bolt forward, feeding a paintball into the barrel. At the same time, it drives a hammer into a valve, opening it and allowing air through the ’gun to fire the paintball. When the solenoid switches back, it cycles the ram back to the starting point, pulling the bolt back and allowing the next paintball to feed. All just like an Angel, Bushmaster 2000, Defiant, or Tribal.

The twist with the Impulse relates to the air flowing to the solenoid. This electronic valve is fairly delecate and is not designed for the 300-500 psi operating pressures that other electros need to achieve 300 fps velocities. This requires a low pressure regulator (LPR), a sort of step-down regulator that lowers the pressure being fed to the solenoid to a more reasonable 80-100 psi which the valve can handle and which is more than enough to drive the ram.

The Impulse borrows a page from the Shocker manual, operating at pressures in the 150-200 psi range (the ’gun I tested actually achieved 285 fps at an input pressure of 140 psi). Though some feel that even this is too much pressure for these valves, these same pressures have been run through these same valves in the Shocker for years. As a result, the Impulse has no need for an LPR. The cylinder under the barrel at the front of the ’gun is nothing more than an empty chamber to provide more air volume to feed the valve. No LPR means fewer parts, fewer things that can be improperly set, fewer things that can break, and a lower final cost for the consumer.


The Impulse comes with a lot of features that have come to be expected on any paintgun with high-end or tournament intentions.

Start with the center-feed body. This feature only just reached the Shocker this year. With the Impulse, center-feed is standard. Though the final prototype sent to me had a cemented-in, slip-in feed adapter, all production Impulses have the feed tubes threaded in for a snug, reliable fit. This will also make room for the possibility of high-rise feeds from aftermarket manufacturers.

The body itself mirrors some of the ’guns with which it shares so much. The tall body, stacking the bolt over the ram over a pan with the solenoid and electronics is more than just a little bit reminiscent of the Bushmaster 2000 and Defiant. Though photos in the Smart Parts catalog show a dull, boxy prototype, all production models mirror the ’gun I was sent to review. The body has been nicely sculpted with smooth, subtle curves that give the ’gun a family resemblance to the Shocker 2000 center-feed.

The bolt has gigantic inlet and outlet holes to allow for the very low operating pressure. Just like the Bushmaster, the bolt rides in the top of the body and is coupled to the ram below with a push-pin inserted through the top of the ’gun. In another irritating parallel, your hopper sits directly in the way of removing this pin when installed.

The pan holding the electronics are coupled to the body with the same two beefy screws that hold the grip frame in place. There is some particularly nice design involved here. First, the grip frame is cut such that simply loosening the two screws allows the back of the grip frame to be pivoted to the side off the back screw and then slid backwards off the front screw, allowing you to remove the grip without taking off the pan. The two beefy screws have heavy threads that are not likely to strip (take that BM2K), and the wires have ample slack and are securely attached to minimize the chance of their being torn loose.

Thankfully, Smart Parts is including a power-switch on the left side of the pan so you don’t have to disconnect the battery to shut the Impulse off (this feature has also finally found it’s way into the Shocker while, ironically enough, the Angel has gone in the other direction). The dwell does the same thing in the Impulse as in other electros; determines how long the ram is held forward. The impulse has a hole cut in the right side of the pan, allowing quick and easy access to the dwell pot for easy adjustment while firing over the chrono. Higher dwell settings allow you to use lower pressures.

The electronics hidden in the pan above the grip frame can be had with the same options you can have in a Shocker: standard, select-fire, and turbo boards are all available. The ’gun sent to me had the new turbo board. Smart Parts was the company that came up with the whole idea of turbo in the first place. The original turbo option in the Shocker was basically standard semi-auto until you started pulling the trigger more than 2 or 3 times per second, at which time it would promptly go full auto. OK, so it didn’t technically go full-auto. It was actually buffering switch bounces that were normally filtered out and discharging them at the paintgun’s maximum rate of fire. The end-result was effectively full-auto fire at the ’gun’s maximum rate as long as you kept pulling the trigger 2-3 times a second. Now that everyone knows what turbo does and other ’guns are coming out with similar fire modes, Smart Parts is redefining the whole thing. Now, rather than kicking in at low trigger-pull rates, you need to be pulling the trigger much faster to get turbo to kick in. In fact, it’s been redesigned in such a way that all it really effectively does is space your shots out evenly at high rates of fire to minimize the chance of chopping a ball. Smart Parts claims that with the ROF turned way up, turbo becomes noticeably more like it used to be, but since turbo is not tournament legal at rates above 8-9 shots per second, that doesn’t mean much.

The grip frame houses the battery: a standard 9 volt, thank goodness, rather than the expensive proprietary battery Smart Parts uses in the Shocker. Hiding the battery behind the rubber, finger-groove grips makes it much easier to disconnect and replace than in the Shocker and Bushy.

The frame itself is a .45-style frame with a 2-finger trigger and full-size guard. As with most 2-finger trigger ’guns, there is no room behind the lower trigger part if you choose to shoot single-finger. The trigger itself is a nice, wide plate in contrast to the Angel’s thin trigger. The trigger is very loose, has a lot of slack in all directions, and has a fairly sloppy feel. For the record, Smart Parts did that intentionally. I’ve seen a lot of electros that would discharge if you bumped them too hard. Not particularly safe. Those familiar with Smart Parts know that they’re so heavily weighted down with attorneys that it’s only a matter of time before they end up suing themselves. A twitchy electric trigger that is entirely too easy to accidentally discharge doesn’t look cool to a lawyer. It looks like a personal-injury lawsuit waiting to happen. To make it virtually impossible for this paintgun to accidentally discharge they left a lot of slack in the trigger’s action. It still fires over a distance no bigger than a mouse-click, there’s just a lot of extra action around that point. Clever airsmiths will undoubtedly stop this trigger out to tighten it up and bring it down to dangerously short lengths again.

Up front, Smart Parts includes one of their own (surprise!) 12" Teardrop barrels. Rather than doing something as blatantly sensible as making the Impulse barrel thread pattern compatible with another ’gun (the Shocker would be a reasonable choice), they’ve given the Impulse it’s very own new threads. Don’t look so shocked. Smart Parts makes the bulk of their money selling barrels after all.

The Impulse is requires a low pressure input to operate so a regulator with high flow and good low pressure performance is a necessity. No surprise, the base Impulse comes with the new, shortened, bottom-line Max-Flow regulator set up to take a CO2 tank, though higher capacity CO2 and nitrogen systems are available as an option. Yes, like the Shocker the Impulse can be run on CO2 as well as nitrogen - a boon for players who can’t afford an expensive nitrogen system or who don’t have HPA fills in their area. If you do use CO2, it is highly recommended that you use a tank equipped with a properly fitted anti-siphon tube to minimize the chance of drawing liquid.

The Impulse I tested came with a pair of options that do not come on the basic Impulse. They are the Gadget forgrip and the drop-forward for the Max-Flow system. Though neither is an absolute necessity, both improve the balance and feel of the Impulse dramatically.

Finally, they sent along a 20 oz CO2 tank with one of Smart Parts’ new on/off valves which turns on to off over only 1/4 turn of the small blue knob. Better yet, you can easily turn the valve with your fingers even with a full tank - no wrench required.


When completely assembled, the Impulse with Max-Flow on a drop-forward makes for a tall package, much like other stacked electropneumatics like the Bushmaster, Defiant, and Tribal. Despite it’s height, the ’gun has a fairly short length, and even fully set-up to play, this paintgun feels very light and maneuverable. Part of that impression is almost certainly due to the absence of the comparatively large and heavy nitrogen tank I’m accustomed to hauling around. Accounting for that, though, this is still a very light paintgun with very little excess metal to weigh you down. With the Max-Flow mounted on a drop-forward, the balance with a 20 oz tank and full hopper the ’gun is quite well balanced. I wouldn’t particularly like it without some sort of drop-forward as it would tail-weight the ’gun and force me to hold it at an uncomfortable distance.

The trigger, as I mentioned before, feels quite loose and sloppy. As with all electropneumatics, the return springing is very soft. Though I’d naturally prefer a tighter trigger with less slack (like that found in the Angel LCD, for instance), I found it very easy to find the sweet-spot in the trigger pull where the Impulse is triggered to cycle. Just wiggling the trigger back and forth through that point allows easy rapid fire and extremely high cycle rates. Some people who tried it actually preferred the longer trigger pull to the ultra-short ones that are typical in other electros - something to keep in mind if you like a bit more range of motion in your trigger pull. When it comes to rate-of-fire, the Impulse doesn’t give up anything to any of the fastest electros. It’s just not as obviously easy to do due to the slop built into the trigger in the name of safety.

Is the trigger really safer? Good question. The thing is still very softly sprung and doesn’t require much force to coax it into cycling. More than once, the Impulse went off in my hands as I slid into a bunker, blasting two to three shots into the back of my cover if my fingers bumped the trigger. Naked Dave actually shot himself in the foot just standing and waiting for a game to start. On the other hand, unlike the Bushmaster, the Impulse never went off in the staging area while I was carrying it along by the forgrip. While the built-in sloppiness of this trigger prevents it from cycling when the ’gun is shaken, the big, two-finger trigger is a big target that is very easy to move. Suffice it to say, the safest way to transport this paintgun is with the power-switch off.

The new turbo mode is, I’m sorry to say, a complete castration of what was once an enhanced mode of fire. Where before you had quick and easy access to extremely high rates of fire when you needed it and standard semi-auto when you didn’t, now you get little more than a more even spacing of your shots when really shooting fast. In all honesty, I flipped the switch back and forth between turbo and non-turbo modes and could never tell the difference. Given that this option adds something like $150 to the price of the Impulse, I just can’t see any good reason to add it.

Feeding the Impulse’s high rate of fire was no problem with a standard motorized hopper despite the low-rise feed tube. Accuracy was, as always, as good as my paint and barrel would allow. I’ve had good luck with the Teardrop barrel before and got a decent fit with the Diablo Blaze I was shooting. Personally, I’d probably prefer a 14" All American barrel, but given the price point they were aiming for, the Teardrop is a fine barrel that shoots very nicely with most mid-grade paints. I do feel that the Impulse kicks a fair amount when fired, particularly in comparison to the Angel. The reason for this is not too hard to fathom. The bolt in the Impulse is quite a bit heavier than that found in the Angel. Moving this much mass this quickly offers an obvious example of Newtons laws in action. Substituting a lighter, plastic bolt for the aluminum stocker would likely reduce the kick substantially. Though I did find the extra kick to be distracting at first, it wasn’t too hard to acclimate to and I didn’t think it had a significant impact on my accuracy.

The CO2 performance of the Max-Flow and Impulse was just fine. No problems at all while I had it, though I have to admit that I only had the opportunity to use it in the midst of this warm summer. I’ve seen Shockers running CO2 left in a cold car overnight freeze solid the next day and refuse to operate. As the Impulse uses many of the same parts found in the Shocker, I’d strongly recommend keeping it above freezing temperatures before taking it out to play if you plan on using CO2 as your propellant.

Fortunately, CO2 should not be as much of a necessity with the Impulse as it has been with the Shocker. The Impulse actually provided pretty decent efficiency. I managed to get something like 1200-1400 shots from a full 20 oz tank. Expect just over 1000 from a 68 ci 3000 psi nitrogen system.


Rather than being original and innovative, the Impulse is quite obviously, both visually and functionally very reminiscent of several other electropneumatic paintguns on the market. Rather than commanding a top-of-the-line price tag like the Shocker 2000, the Impulse comes in at a bare-bones price that will have even the cheapest tournament players giving it a second look. Where the Shocker sucks down air faster than Cesare inhales pasta, the Impulse actually gives a fair number of shots from your full tank. And where the Shocker went through a long and painful period of growing-pains, the Impulse has obviously benefitted from Smart Parts’ long experience and is shipping new as a much more polished and complete package than the Shocker did in the first few years of it’s existence. As I said at the start, near opposites in many ways.

On the other hand, the Impulse shares with the Shocker it’s low pressure operation, ability to run on CO2, and fast electric trigger.

So what’s the cost of this neat little package? Try $500 including the Max-Flow regulator. Add the forgrip and drop-forward for another $40 or so and you’re still looking at a high-end electropneumatic paintgun built to operate like the twice-as-expensive Angel for under $550. It’s really not fair to compare this ’gun to the more refined and feature-laden Angel, but it’s perfectly fair to compare it to the Bushmaster, Defiant, and others of that ilk. Not only does it undercut the price of all those piantguns, but you aren’t stuck laying out for an expensive nitrogen system in addition (something that most other electropneumatics require). The Rainmaker is a fine paintgun and an electropneumatic to boot, but it really isn’t in the Impulse’s class as it comes stock from the box.

Furthermore, the Impulse will eventually be available in all of Smart Parts’ colors, fades, and splash patterns. That and the different board upgrades (select-fire and turbo) are expensive ways to trick out this paintgun. They’re fine if that’s your thing, but you lose the substantial value advantage that the Impulse brings to the table at this exceptionally low price point.

In the final analysis, the Impulse is a lot of paintgun for the money. If you’re in the market for an inexpensive electropneumatic, you aren’t going to find one that offers as much bang for the buck as the Impulse. Though it has a strong kick and an unrefined trigger, this paintgun offers a lot of very nice features and small design refinements that really impressed me. Though it’s certainly not for everyone, the Impulse is certainly going to make a lot of people very happy.

All material at this site is © Ravi Chopra, 2001