Chinese Invasion!

Qian Wei S-4 Review by Have Blue

Some time ago, people started noticing some interesing guns appearing at the website (run by the Taiwanese equipment maker Qian Wei).  The most notable was a frightening looking double barreled, wood-stocked semiauto monster designated only 'S-4', reminiscent of Sheridan's well-known KP rifles and even moreso, Palmer's infamous, rare, and very expensive Nasty Hurricanes.  In order to bring this beast to the firepower-loving players in the US, Kyle Dobbs started to import the S-4, and in the future, other Qian Wei guns as well.

I ordered a pair of S-4s from Import Paintball - one for myself and one for my friend Dan, who runs the local paintball store (shameless plug: Brushfire Games - best paintball shop in SE Wisconsin).  The guns arrived in a plain cardboard box with quaint Chinese printing on the outside.  Inside was an exploded diagram of the gun and a note from Import Paintball which gave a few tips on operating and maintaining the gun. The gun itself was packed securely in a styrofoam cutout, with the barrels, tank and feed necks removed.  I attached the feed necks, screwed in the barrels and tank, and admired this foreign marvel.  Wow, what a beast.  Has a very solid feel (though the stock is made from a rather lightweight wood, probably pine), and very front heavy - this one's a two-hander, for sure.  It weighs in at 5.8 pounds without a tank, paint or hoppers, showing right away its VM-68 heritage.  Being a hopeless tinkerer (and not having any full on/off tanks handy, but more on that later), I then immediately began to disassemble the gun.

The barrels are two-piece, with a muzzle brake that screws onto the end.  Although many of the gun parts appear to be interchangeable with VM-68 parts (or very nearly so), the barrels do not have any sort of shank - the threads go all the way to the end.  The threads are also notably smaller than VM-68 threads - as far as I know, the S-4 does not share the same barrel threads as any other gun.  Bore size is a hefty .696", with the muzzle brake being 0.75" inside.  Internal finish isn't half bad.

These two screws are all that hold the stock onto the rest of the gun.  Should the trigger frame be removed from the gun, it would be advisable to use a plate or washers under the screw heads to keep them from pushing through the soft wood.  Making a tank mounting bracket ala KP-3 would be a nice modification, as it would mean less stress on the stock while improving the gun's balance.

Note that the longer of the two screws goes to the rear (due to the taper of the stock).  The "S-4 Launcher" logo screened onto the side of the stock rubs off very easily - should you wish to preserve it, a coat of lacquer would be advisable.

The feed necks are just like those used on the VM-68 and Equalizer.  Unfortunately, Pro-Team powerfeeds certainly won't work, as they'd be in each other's way.

The bolts in the forward position without the barrels in place.  The entire body of the gun is very nicely finished in a tough satin black anno that should prove very durable in use on the field (note that there are also teal blue and camo anodized versions available).

The rear plate is held in place by a single screw, and the two end plugs hold the two mainsprings in place.  The instruction sheet that Import Paintball supplies with the gun indicates that the two mainsprings should be clipped slightly to bring the gun's velocity down to a reasonable speed (note that the gun has no simple means of velocity adjustment).

A solid pin through the front of the hammer keeps the two bolts linked together. The air inlets on the bolts are located between the rear pair of o-rings.  The hammer is very much like of the VM-68 - big, long and heavy, giving the gun a pronounced kick when fired.  Also note that the cocking knob can be flicked sideways into a slot to 'safe' the gun like on the VM-68.

All of the o-rings on the gun are remarkably hard - much closer to a plastic than the Buna-N or neoprene o-rings that we're used to.  A close eye should be kept on the striker o-ring - the gun has a tendency to be a bit rough on this seal, and as it gets chewed up, it tends to bind in the forward position, making (re)cocking difficult.  Unfortunately, the striker o-ring is just a hair too large to be replaced with a common tank o-ring.

A look down the inside of the gun from the rear shows the valve in the center.

Quite thoughtfully, Qian Wei has included a valve removal tool with the gun.  Note that the two valve screws are of slightly different length - the shorter one is located on the bottom side (due to the flattened lower side of the body).

Again very similar to the VM-68, the valve has two sets of ports located perpendicular to each other - the valve can be rotated 90 degrees to align the smaller or larger ports with the bolts to serve as a coarse velocity adjustment.

A look at the rear end of the valve shows the square cut blowback port.  It seems that this port just isn't quite large enough to reliably blow the hammer back fully - if your gun refuses to recock, I'd recommend using a very small triangular needle file to widen out the corners, allowing more gas through.

The valve stem would be a good start for airsmithing on the gun - by shaving down the top portion of the stem as in 'turbo' valves, the gun's anemic efficiency should be boosted somewhat.

A hole has been drilled through the right side of the body and then capped off with a set screw to provide air channels to feed gas from the valve through to the bolts.

Again taken from the VM-68, the trigger group shows its lineage.


Watch out for that pin in the trigger group - it'll fall out if you so much as look at it sideways.

For those unfamiliar with the VM-68, the sear functions in a unique fashion.  Pulling the trigger lowers the sear, allowing the bolt to be driven forward...

...which knocks the catch plate forward, disengaging it from the sear and allowing the sear to rise up, ready to catch the bolt when it returns.  When the trigger is released, the catch plate will once again lock onto the sear.

The ASA is unfortunately without a depressor pin - you'll need to use a tank with an on/off valve or hook up a remote.  However, the ASA does have a sintered filter element, a very nice touch.  Perhaps China has even more problems with 'dirty CO2' than we do!

The tank is an odd one - Qian Wei calls it a 'gas vase'.  It's a slender steel tank, with a very large on/off knob on the bottom (all of the tanks on appear to be like this).  Like the ASA on the S-4, the tank also has a sintered filter, but alarmingly absent is any sort of rupture disk (that I can see).  Unless the internal on/off assembly has some sort of overpressure release, I would strongly uge people to avoid using this tank (should you choose to try using it anyway, put no more than 3 oz. in, as the total tank capacity appears to be just a hair under 4 oz. - far under the 7oz. that had been published on , the early home of

O-ring sizes
#4041 - 0.530" ID, 0.715" OD (front valve o-ring)
#4042 - 0.540" ID, 0.720" OD (foregrip gas o-ring)
#4043 - 0.560" ID, 0.715" OD (striker o-ring)
#4044 - (bolt o-ring) unknown size, no extras supplied, and they're a real bear to take off the bolts
#4045 - 0.520" ID, 0.725" OD (rear valve o-ring)
#Q9202 - 0.550" ID, 0.710" OD (????)

Note that these sizes are as I measured them - your mileage may vary.  Some were slightly out-of-round and others had a good deal of flash from molding.  Should you need to replace one, I wouldn't worry much about trying to get the exact right size - for static seals like the valve o-rings and foregrip gas o-ring, you've got a decent amount of leeway in selecting an o-ring.  For the striker and bolt o-rings, you may have to search a bit.  The striker o-ring seems to be just a little bigger than a tank o-ring (and the spare striker o-ring that came with my gun seems to be a bit too small even).  I had the best luck with using a 3/8" ID x 9/16" OD, 3/32" thick o-ring that I got at the hardware store (Danco out of Condcordville, PA is the maker - they usually have a display of o-rings in the plumbing section of most decent hardware stores).   Should you need a bolt o-ring, you should be able to use the second bolt o-ring from the bolt face as a spare, as this one really isn't necessary.

24JUL2001 - I still haven't used my S-4 in a game.  Heck, I've put very little paint through it, and it now sits disassembled in a box, awaiting yet more polishing on the trigger group and other tweaks to hopefully get it running halfway reliably.  Several changes have been made to the S-4 in current production version according to Qian Wei, and this photo from their website certainly shows a slightly different version than my own gun:


Although this photo appears to show the old feedblocks, currently produced models supposedly have welded-on feed necks, a feature which doesn't exactly have me hopping up and down with joy.  Note that not many airsmiths will touch this gun.  One prominent airsmith took a stab at getting it to run well, and though he succeeded, the undertaking took far too much time and effort and now he won't touch an S-4 again.   Jackel has had some success in getting two different S-4s working and says:

One was a new style the other was an old style... The kicker is that most of the orings are crap... I bought a VM-68 spare parts kit replace the valve, striker , and even the cup seal.. The bolts I then swapped out for a pair of VM star fires and then later made my own out of delrin....

The point to getting the thing to run is it must be cold not to cold or it wont work , but like 50 degrees cold and running on liquid then it should work...

As for mangeling the Oring on the striker.. I hit that area with a brass brislted NAM brush it used to be used to finish off flex honing but it works for this as well... it opened it up maybe.. .01 but I havent busted that oring since.

Jackel also adds that gas consumption is horrific on the gun - running dual 20oz. tanks (one on-gun, one remote) gives him only around 500-600 shots total!  Not all is bad in the world of the S-4,though - Kevin Gosingco wrote me to say:

I just wanted to inform you that Steve from can make brass barrels in any length and bore size. I'm the first one he's made barrels for for the S-4 so if you like I can update you on the performance. I bought 2 brass barrels in a 12" length with a .688 bore size. He had quickly checked the bore size of the original stock barrels and was surprised to get a reading of .70!

Steve from BOA then dropped a line about the threads on the barrels:

Barrels for it are a blend of the spyder and VM. Cutting the neck off a spyder barrel will probly work, but i never got to try it while I had Kevin's gun.