The Gun From Hell

Auto-cocking Nelsons?

I refer this particular paintball marker as “The Gun From Hell” basically because it has been… the gun from hell. Out of all of the paintball guns I have owned since I started playing in 1989 (over 40), this has been the single most frustrating, nerve-wracking, money pit I have ever had. But I like a challenge…   It began in 1991 when I came across a Worr Games auto-cocking kit made for the Trracer at the Line SI Masters (now the Zap Masters) in Nashville, TN. At the time, the actual “from the factory” Autocockers were just coming onto the scene. Most autocockers I had seen up until then were Sniper conversions. For $250 you could send Worr Games your Sniper and get an Autococker in return. The kit for the Trracer cost about $180 at the Worr Games booth at the Masters trade show. I later saw it advertised in magazines for only a few dollars more. To my knowledge, it is no longer in production, but a few are probably still floating around. The kit included a grip frame, trigger assembly, pneumatics block, hoses, bottom-line adapter and shroud. It came with the same pneumatics as a standard Autococker. With the exception of the sear and direction of hammer travel, function is identical to an Autococker.
The thought of turning one of my accurate, awesome shooting pumps into a semi-automatic thrilled me, especially considering the performance of the open bolt semi’s at the time. When I bought the kit I did not have a Trracer on which to mount it. The first couple of incarnations of the gun appeared with several Nelson type bodies including my Bushmaster Deluxe. Eventually I got a Maverick Deluxe (same as a Trracer) to serve as the body for The Gun From Hell. Although this was the body for which the kit was designed, this change alone did nothing to address the problems.

The biggest problem I encountered with the gun was having the timing come out of adjustment. I would adjust it at the beginning of the day, and by the end of the day it would not be functioning properly, or sometimes not at all. Another problem was the pneumatics would literally beat the internal parts to death. Timing problems and excessive wear also plagued earlier Autocockers. One of my teammates had bought an Autococker about the same time and he eventually gave up on it, and sold it. I was encouraged many times by my friends to do the same with this gun, but fortunately for me, I did not have to rely on it as my only gun.
Different Strokes
Just as is often the case with Autocockers, a good deal of the timing problems came from the operator’s (that’s me) lack of understanding of how the system works. As I see it now, back in the days when I first had the kit, getting the timing right only happened because I got lucky – certainly not because I actually understood what I was doing. As the violent action of the gun caused it to come out of adjustment, I would not really know which way to go to put it back. I would simply guess until it worked good enough for me to use, which sometimes meant the gun would fire when the bolt came forward and closed (auto-trigger effect). Although this was usable, it diminishes performance and is not the way the gun is supposed to work.

The way the gun is supposed to work is actually quite simple. The trigger pull activates the pneumatics, which perform the same function as manually pumping a Nelson based gun. When you pull the trigger, the first part of the trigger pull releases the hammer sear. The compressed main spring moves the hammer backwards, it strikes the valve open and the gun fires. As you continue the trigger pull, the attached timing arm directs gas through the 4-way valve into the ram. The cocking rod in the ram moves back, carrying the bolt with it. The main spring is compressed between the bolt and hammer as they lock together via the hammer sear. When you release the trigger, the timing rod comes forward, directs gas from the 4-way to the other end of the ram, and the gas pushes the cocking rod and bolt/spring/hammer combination forward.

Problems can occur in two major areas during the process. One of those concerns the cocking lug adjustment on the cocking rod. The lug threads onto the end of the rod. It must be adjusted to fit the particular gun on which the kit is mounted. The easiest way to do this is as follows;

1. Make sure the bolt is fully closed (forward)

2. Make sure the cocking rod is all of the way forward.

3. Adjust the cocking lug until it is properly aligned with the hole in the bolt and you are able to put the connecting screw in without having to move the bolt or cocking rod.

This part of the design is where one of the adjustment problems lies. The ram cocking rod itself can rotate during firing, which means the lug will slowly change it’s position on the threads, and eventually work it’s way out of adjustment. I tried using a thread-locking compound, and pipe tape, but they did not seem strong enough. My best solution was to put a nut on the cocking rod and tighten it up to the lug.  This could probably damage the cocking rod if over-tightened. Another possible solution would be to drill and tap a hole for a set screw in the lug itself.

Timing Stands Still
The other major area for adjustment problems is the timing arm. Different Nelson type guns have slightly different internals, especially concerning the hammer sear. The timing needs to be adjusted so that the gun fires before it is re-cocked. This adjustment can actually be made without air if one knows how to cock the gun without air. This is done by pulling the valve body off the back and pushing the hammer toward the bolt by sticking a large Allen wrench, etc. in the back of the gun. When the hammer is pushed forward it will lock up with the bolt. The adjustment can also be done with air on the gun, assuming your timing is not so far off that the gun can still cock. I use the following steps to adjust the timing arm;
1. Undo the set screw on the timing arm.

2. Pull the trigger slowly until the gun fires (hammer sear releases) and stop your trigger pull.

3. Holding the trigger in that midway position push the timing arm all of the way forward.

4. Lock down the set screw.

This can take some repeating and fine tuning, and by tinkering you can get it right on the edge, but the idea is to be able to release the hammer sear before the trigger actually engages the timing arm and pulls it back. That’s what the oval shaped hole in the trigger is for – to allow movement of the trigger before the timing arm activates the 4-way. If the 4-way is activated too soon, the bolt chases the hammer and spring backwards, and helps hold the valve open for a longer than desired interval. This results in a sudden “really big” gush of gas being released, which can cause all kinds of unwanted effects, including leaving paint dripping from the tip fo the barrel to the top of the hopper.  If the gun is operating properly there should be virtually no blow-back up the feed tube (which makes an agitated loader necessary for rapid fire).

One of the common problems people who still have this kit often face, as I alluded to before, is the gun firing automatically when the bolt comes forward to close.  Before I understood what was happening, I had used the gun in this mode myself, and have met others who did the same.  If this is happening, your timing arm is too far toward the back, and not allowing the trigger to return all of the way forward. The result is that the trigger is already in position to release the sear when as the hammer/bolt comes forward (just like holding down an auto-trigger on a nelson type pump) and the gun automatically fires. If the gun is firing before the bolt is fully closed, it can diminish performance in number of ways including:  1) you can break balls and get a lot of blowback up the feed tube.  2) The hammer will not be traveling it’s usual full length, giving you less than a full power shot.  3) You are in effect, reversing the process, and the gun cycles before firing each shot, as opposed to firing first, then cycling –  hence, your closed bolt gun is emulating an open bolt gun.
Maverick Moments
I have been mostly pleased with the Maverick Deluxe body on the gun. The Maverick in itself is a very good pump gun for the money – holds a consistent velocity, and has relatively good accuracy.
One recurring problem I have experienced with the Maverick is a leaking cup seal. This has also been the case for friends of mine who have regular stock pump Mavericks and Hornets. It is a very small leak, and not debilitating or detrimental to game play (unless you are using 12 gram), but it is nevertheless a leak… And just when you think you have the problem solved, it re-appears.

Adjusting velocity on the Maverick-bodied Gun From Hell is a little more difficult than with more standard nelson type guns with a down-the-barrel type adjuster. Because the Maverick’s hammer includes a tube that inserts into the bolt, the bolt’s velocity adjuster cannot be turned when the gun is cocked (bolt and hammer hooked together). This is not a problem on a normal pump gun – just fire the gun and make the adjustment before cocking again. On the autococking version the simplest way to “de-cock” the gun is by removing the screw that connects the cocking lug and bolt, then fire the gun. Make your adjustment, put the screw back in, then pull the trigger to re-cock the gun. Before you pull the trigger again, remove the screw once more so the gun will de-cock after firing again, in case you need to make further adjustments. If you don’t need further adjustments, just put the screw back in, and pull the trigger to re-cock.

Hard-wear
The not-so-adjustable pneumatics regulator that came with this kit is undoubtedly designed not to allow failure of the cocking action, under any circumstances. However, that can mean an awful lot of power is used to automate this thing when less is needed. That is one of the reasons I put aftermarket pneumatics on the gun.. (that and the fact that I had nothing better to do with $90.. yeah right.) I have been mostly happy with the performance of the ANS products on the gun. The adjustable regulator allows me to use just enough pressure to cock the gun, as opposed to “all I need and then some“. The ram seems to operate smoother, quicker and require less pressure. Overall I don’t notice the amount of wear, such as what appears on the cocking slots, as I did with the stock pneumatics. One thing I have noticed is that the pneumatics regulator needs to be adjusted when adjusting velocity upward or changing to a stiffer main spring. Not because the pneumatics regulator has a direct effect on velocity, but because increasing tension on the main spring of the gun requires more pressure to be sent to the ram for cocking duties.

Sometine in 1998 I bought an ANS Gen-X regulator to put on The Gun From Hell as a way to control the pressure going into it. I figured this would accomplish several things; keep a consistent pressure so that I would have to make less adjustments on velocity and the pneumatics regulator, allow me to experiment with low pressure operation, and spend yet more money on The Gun From Hell (is this name making sense to you yet?).

A note about the following test: It was done on two separate days in temperatures averaging about 90 degrees. I was using fresh Zap paint, because it is a larger bore paint and well suited to the stock barrel for this purpose. Also, all pressures described were as indicated on the gauge that came with the Gen-X regulator. I have no way to verify it’s accuracy, although I am fairly confident the relative increases and decreases noted in the test are accurate (in other words, if the accuracy of the gauge was 50 psi low, then you would add 50 psi to all of the numbers below).

Right off the gun operated with semi-decent velocities (270fps) on an indicated 600psi, which is basically running the reg wide open. This would not do so I set about trying to reduce the needed operating pressure, which would require a larger volume of regulated gas. My first step was fix a volume chamber to the back of the gun… I found this part in my parts box and have no idea where I acquired it.  It is basically a hollow tube with standard bottle threads on each end, and a pin depressor. I think it was some kind of extension for back bottle set-ups. This piece alone didn’t have much of an effect due to the fact that the air flow into the actual valve chamber was greatly restricted by the small hole in the valve body. So the next step was to increase the air flow. I did this by very carefully drilling (on my drill press) two additional holes of the same diameter through the body. On the left is the modified unit, while the stock unit is on the right. This operation requires fairly precise drilling, as a mistake could easily open up the valve body to the outside world, and ruin it.  The frame screw hole in the valve body runs beneath the pin depressor, which is certainly an area where no holes should be drilled. Note: I usually don’t make serious mods unless I have an extra part lying around, which in this case, I did (an NW89 valve body that coincidentally works with the Maverick).

Opening up the air passage and using a lighter valve spring produced a dramatic increase in velocity. At 600psi the gun initially shot anywhere from 289 to 310 fps, with one of the first few being a double loaded shot which left paint in the barrel (some idiot left the anti-double-feed spring out of the gun the last time he re-assembled it). The velocity stabilized near 300 fps. One interesting note is that twice the gun fired a string of 6 or 7 shots in a row at exactly 298 fps, only varying off a few fps between the two strings. After cleaning the barrel I headed back to the chronograph and this time got the initial shots between 329 and 313 fps until the gun settled at an amazingly consistent 323 fps, occasionally dipping to 320 fps when I fired a little faster. I backed the regulator off to about 450psi where velocities dropped to near 270 fps (where I was shooting at 600psi before the modification of the valve body). I brought it back up to an indicated 500 psi which gave a consistent 286 fps (with occasional + or – 3 fps).

My operating pressure for similar velocities had dropped between 100 and 150 psi. Not bad for the work I put into it, but certainly not “low pressure” by today’s standards. It does, however, allow more space to regulate the Co2 going into the gun.

As a side note here, I have tried this gun several times with my 4500psi HPA tank, and the gun didn’t like it. The gun tended to use a large volume of air and drain the 68ci tank rather quickly, not to mention producing some rather strange fluctuations and an odd sound from the valve system. I don’t think the compressed air expands quick enough to move through this valve properly, but that could be an entirely misguided deduction on my part (wouldn’t be the first time!). I am sure there is someone out there who could explain this better.

Odds and Ending
Another modification I made was the method of supplying gas. The kit came with a standard bottom-line adapter with an extra hole drilled and tapped for a second air line. One line would go to the pneumatics block while the other went to the ASA. I replaced this method with the red Cooper-T adapter, which is basically an ASA with a side tap for a hose. It allows the use of a vertical bottle, standard regulator, etc. On the adapter I placed a quick disconnect fitting. This allows me to remove the valve body of the gun without having to undo any hoses or hard parts. The matching red trigger shoe replaces the ill-fated plastic piece that came with the kit.

The latest incarnation of The Gun From Hell features the body from a Wintech pump (a bore-drop Bushmaster clone),  Lapco internals, and a Bob Long Regulator. Whether it will stay that way for a while, return to the Maverick body, or something else, remains to be seen.  I have little doubt the gun will eventually change again as I currently own around 10 different Nelson-style bodys and a variety of internal parts. Over the years the gun has certainly been more fun to experiment with than to use on the field. Not until recently has it become reliable enough that I would actually burden someone else by letting them play with it. Normally, I only torture myself with my more unreliable equipment, so letting other people use the gun says something good about the confidence I have developed in it. The cost of the gun and all of it’s associated parts exceeds $500. A lot of people would waste little time in pointing out how that money could have bought me an entirely better gun, but considering I made that investment over an 8 year period, and learned a lot along the way, it’s not as bad as it seems. I also have the advantage of having something fairly unique – and it’s something that actually seems to work well now. Of course, “now” is an extremely relative term – after all, this is The Gun From Hell.