Steely Slide Stopping Success

Is it wrong to be this exctited about a fairly small piece of technical innovation? If it is, I don't want to be right.

Around a year ago, I bought a second hand, run down KJW KP-08 with the hopes of fixing it. The four CO2 magazines that came with it had leaky valves, but most other things seemed to be in ok-ish working order. I put the gun and mags in a box and stored them for later. Once I now finally got around to replacing the valves and testing the magazines, I was faced with a new problem.

The old, original slide stop was so worn down that it would not stay put in the gun when shooting, and eventually decided to attempt evacuation at the most inopportune moment. The result (as best I can deduce and reconstruct the events) was that the slide slamming backwards hit the stop, and broke it in two.

At first I thought of just getting an original replacement part, but I've had my fill of pot metal parts lately, and decided to shop around a bit. That's when I came across this KF Airsoft steel slide stop for the Hi-Capa. I thought it brilliant, as I would not have to worry about it breaking again. Once it arrived, though, I was pleasantly surprised even further.

In addition to the stronger-than-original build material, the take-down pin is not a single piece, but a sleeved structure. What this allows is for the weight and force of the slide to rest on the sleeve, leaving the actual slide stop lever to rotate freely inside. In other words, you can have the take-down pin as tight as you want without it affecting how the stop itself functions. This is simply brilliant. I don't know who originally designed this, but it's damn marvelous!

As with all things airsoft, though, some modification was necessary.

As seen in the above image, there's a metal nub protruding from the inside of the stop, which would hit the feed lips and the side of the magazine, preventing proper seating and functioning. So, what else was there to do but break out the file set and get to work?

I filed down a bit, tested the fit and worked until nothing pushed against the magazine.

As a result, I ended up taking down the protruding nub entirely and shaving the backside of the retaining tab as well in order to secure proper fit.

I reassembled the gun and had a test fire. I'm now getting a very positive lock with this part. It's better, in fact, than the original one, and it cost just a few coins more than an OEM part!

It's (sadly) not everyday that you come across airsoft parts that surprise you this way. I'm pretty stoked this one did! If you have any similar experiences, please do share them below!

DIY P90 Sling Adapter

The biggest milsim event in Finland is coming up again, and just like last year, I'll be part of the HQ staff. If there was a lesson learned from last year, it's that you need very little gear when you're sitting in a tent most of the time. As a result, I thought I'd take my latest project, the P90, with me.

Alas, the gun has no sling point to speak of. After a bit of research, I found some examples of how you can sling the gun. As it happens, I had previously saved some webbing and plastic buckles from a pair of trousers I had to discard. A thought occurred.

These bits would be turned into a sling adapter in what was to become my first tactical gear sewing project. Luckily, we have a sewing machine handy.

The first bit was simple, just sew the female buckle onto the webbing.

Next, I sandwiched the D-ring between the buckle and the two layers of webbing. I would rather have used a plastic D-ring, but this was all I had available (and I was eager to get going).

It took a few tries to get right.

The flip side is not the prettiest, but it works.

The top side looks quite nice for a first ever project.

The next step was to thread the webbing through the hole on the underside of the gun and tighten it so that when the buckle is closed, the webbing is tight.

The loose end could be pushed into the same hole.

It's not exactly Tactical Tailor quality, but it's mine. I'm pretty happy with this little project. With a single point sling, the gun hangs under my arm at exactly the spot where my hand reaches the grip instinctively.

Do you have any sewing projects you've done? Please share in the comments below.

Fixer-upper Part 4: Classic Army P90

Here we are again. A broken gun up for grabs for cheap on a For Sale site. And grabbed it I did.

Patient: Classic Army Sportline P90
Symptoms: "Has had some electrical issues, been to a tech but stopped working again quite some time ago and has been unused since"

I've never owned a P90 before, but it has been on my get-one-some-day list for some time. This one is from the Classic Army Sportline series, meaning the externals are mostly plastic. Now, the real P90 is mostly plastic as well, so it did not bother me that much, even though usually I'm a stickler for realism in materials. Compared to a real P90 the only thing not of similar materials is the upper receiver. The outer barrel and flash hider are metal, as are the optics rails. Furthermore, metal uppers should fit right in if I ever want to get one.

The gun came with a Swiss Arms C-more style red dot (with a missing front clamp), two hicap mags, two NiMh batteries and a dumb charger. The internals had been upgraded to some degree, but the previous owner did not know much about them. In his words, he didn't know what had been done, the gun had been to a tech twice for electrical problems and now just would not fire at all.

Troubleshooting

It didn't take long to find out that the batteries had simply died. With a fresh 7.4 V LiPo this thing came alive, if only on full auto. Something was wrong with the semi function, and I could hear a rattling sound coming from the inside when the gun was tilted back and forth.

Externally everything seemed good apart from a small crack in the rear of the receiver. The two sides of the front grip also did not quite stay put due to a screw having lost it's threads. Nothing to hinder functionality, that is.

The P90 turned out to be exceptionally easy to disassemble. As you might know, my first gun was an AUG. That was very easy to gut, but this one was even better.

After popping the back plate, you see two screws. Take those out, remove the plate they held down, and the gearbox comes out.

The P90 uses a less common V6 gearbox, so replacements and spare parts are somewhat harder to come by than on your average AK or M4.

The upper receiver can also be removed simply by pressing a rectangular button on top of the receiver and sliding the whole assembly out. I could not help but fall in love with the design straight away.

The modularity was not limited to the externals. The gearbox comes easily apart as well, separating the motor cage, wiring and trigger switches into an assembly away from the main body. No wires to stop you from working, and you can test everything without inserting the GB into the gun.

The problem with the semi auto not working quickly became apparent once I peeked into the trigger switch assembly. A part had broken off from the trigger trolley (seen above still wedged below the trigger contacts). With the piece off, the trolley would simply skip over the trigger switch, not move at all and thus not engage the contacts.

The rattling I heard when tilting the gun was not an extremely short spring as I though at first (the gun chronoed just above 0.6 J), but rather the broken stem of the plastic spring guide sliding inside the spring.

The two main problems had been identified, and I got to work fixing them.

Fixing-upping

In addition to fixing what was broken, my plan also included swapping the plastic bushing for steel ones and re-shimming, fixing AOE, installing a MOSFET, and putting in a flat blade fuse and deans connectors. My plan was to build a CQB beast with a high ROF and moderate power.

Swapping out the broken spring guide seemed rather straightforward, as I quickly found a steel spring guide in my spares drawer. The V6 box takes V2 spring guides, which makes it easy to replace. Or so I thought.

A couple of test shots later the spring was compressed into the piston, which in turn was stuck in the rearward position. In case you've never done it, let me tell you that disassembling the gearbox again with this kind of a mine inside is just lovely. I managed to get it out without issue, luckily, only to have it get stuck again (because of course I had to try it again). It was pretty clear that the spring guide would not work here.

I scavenged another spring guide from an M4 parts box I had lying around, waiting to get assembled. It was otherwise similar, but the end was tapered and, more importantly, it had a diameter that was 0.21 millimetres smaller. The one fifth of a millimetre was all that was needed, the spring did not get stuck. The spring, as well as I, was free to move forward.

Swapping out the plastic bushings for steel ones was pretty straightforward, but they did sit quite low in the shell, and I had to use more shims than I've ever had to before. At some point I began to question whether or not I was doing something horrendously wrong, as the the combined thickness of the pile of shims on the spur gear crossed the 1 mm mark. It worked swimmingly, though, so that's tolerances for you.

Trying to fix the angle of engagement on the piston turned out to come with its own set of problems. The piston head was attached with a tiny nut sitting free inside the piston. I could unscrew the head with ease, but lacking a socket wrench for ants I could not put it back on. Who makes these things? I opted instead for an aluminium double sealed head I had lying around.

My problems with the spring guide had apparently resulted in some structural problems, since at some point during test firing the steel tooth broke off the piston. Luckily I had an old spare nylon piston with it's own plastic piston head that went in after a quick AOE fix, similar to the one pictured above.

My first attempt at fixing the trigger trolley consisted of glue and a several thin layers from a piece of paper towel. I figured a glass fibre style layer cake of material and bonding agent would result in a strong base which I could then file into shape. 

Too bad the plastic wasn't very glue friendly. The glue soaked paper held together fine, it just would not stick to the plastic hard enough to withstand the strikes delivered by the cut off lever. The same exact thing happened with various attempts made with super glue, epoxy and even chemical metal. This was one piece of engineering I was not exactly happy with. A thin piece of plastic subjected to repeated strike forces sounds exactly like a recipe for success.

Since the original plastic was a no-go, it was time to fabricate a stronger part. I chose a piece of sheet metal for the job with roughly the same thickness as the original plastic. After tracing out the shape of the trigger trolley, I cut it out, filed it down to size and rounded off any rough edges.

I drilled a few holes (with a 1.5mm drill bit) into the metal, filed down the original trigger trolley, drilled some holes into that as well and roughened up both surfaces, hoping the epoxy would finally bond well enough. I chose to make the holes canted every which way so that once the glue set, the pieces would not come off each other so easily.

To further address the issue, I cut down the trigger contacts so that the trolley would have more freedom to move up and down (the top piece is cut to shape above, the lower shows the original shape).

Everything was working pretty nicely apart from the fact I was getting triple and quadruple shot bursts on semi. The culprit in the end turned out to be my upgraded trigger trolley. The sheet metal was not as thick as the plastic, and thus the trolley was able to sit higher in its rails before disengaging. This in turn made it so that the cut off would not lift it out of place until the trigger was fully pressed down. I fixed this by epoxying another piece of the sheet metal onto the cut off and filed it to size. No more problems with semi auto! 

To round things off, I made a basic DIY MOSFET out of an IRLB3034 and some resistors. The middle prong is cut off and the negative lead is attached with a small bolt and nut to the back plate. Sturdier attachment, better flow of current.

Wiring up a MOSFET on a P90 can be done exactly like in the AUG, since the trigger assembly is the same. There's one switch and a pair of contacts for the semi, and another for full auto. It's only the movement of the trigger that decides whether the gun fires semi or full auto. On the AUG it's up to the shooter, on the P90 the fire selector limits the movement of the trigger.

All the extra bits and pieces fit in without issue and the gun was mechanically ready for service.

One final fix was to repair the cracked receiver. Since the material is ABS, you can forego glue and use pure acetone, as it melts ABS. My end result is a bit sloppy, but with an unhurried approach, slowly wicking the acetone into the crack, you can achieve a brilliant result. While mine isn't aesthetically as pleasing as it could, the upside is still that the plastic is again one single piece as it was when moulded, not two parts held together by an adhesive layer.

With an 11.1 V LiPo this little beast is pumping out 33 rounds per second at 0.92 J. Right on the money, if you ask me. Now I only need magazines that aren't hicaps and can still keep up with that.

Questions? Comments? Anything you'd add or like to know more of? I'd love to hear from you! 

Battle Group Parola Milsim Event Picture Post

The second to last weekend of July played host to the biggest milsim event Finland has seen so far. Over 600 participants split into five factions spent around 27 hours in actual Finnish army training grounds and surrounding woodland trying to gain the upper hand, or simply to survive.

As mentioned the area comprised of real, actively used military training grounds

The backstory revolved around a civil war, where a monarchy supporting faction (red team) attempted to take over Finland from the democratic loyalists (yellow team). Also present were the UN, civilians from two nearby villages, and a team of mysterious operators from a foreign nation (blue team).

You don't see traffic signs like these every day!

The training grounds are adjacent to the Parola Armoured Brigade, which coincidentally is also where I received my year long military training, and the plot of the game revolved around a locked and boobytrapped underground tank hangar. Both belligerents were trying to get inside the hangar without activating the self destruct which would blow up these strategic resources. Rumours told of a former hangar foreman who had set up the explosives and thus also held the secret of disarming them.

Both sides were thus scouring the area for the foreman while also securing key crossroads and assets, trying to figure out who the blue nation were, interacting with the UN and the villagers and naturally battling each other.

My personal role in the game was sadly rather minimal, as my injured leg prevented me from taking to the field. While the rest of my team, BFN Airsoft were out in full force, I got a job at my side's HQ as a situation officer. Rest of the HQ were unknown to me beforehand, but team mates with each other, and they had the job so well in hand that I mostly tried to remain out of the way. However, it was definitely a valuable learning experience to see how an HQ is run, how they would interact with the organisers before and during the event and what the challenges are when you're in charge of five platoons with unique missions around the clock.

The view from the HQ tent. My team's tent is visible in the middle.

In addition to foot patrols, teams got around using in game vehicles such as four-by-fours, trucks, ATVs, and the organisers had even managed to bring in a real life IFV, a BMP-1!

Here's another sight you don't see every day!

In the end the red commander tried to enter the hangar, only to blow up the charges, destroying all the vehicles inside. It turned out the aim of the foreign operatives was to ensure neither side could get their hands on this strategic resource, and thus played both sides to the best of their ability.

I enjoyed my time even though I never got to see action. The closest I got was when the BMP-1 made a rush for our HQ, and we had no antitank weapons at hand. They basically ran over all our defences, and we at the HQ decided to opt for a self destruct so the enemy would get no intel. To our amazement they then proceeded to just mill around for a while, never even took a look inside the HQ tent, and then proceeded to leave us completely alone!

Good times, and I can't say I wasn't at least a bit wistful seeing my old stomping grounds 14 years later.

In order to not have a blog post that has nothing to do with teching, I present to you a fantastic field repair job I did on my Kalash/CYMA AKMS.

The L-shaped hop up retention piece had gone missing, and I noticed because of that you could accidentally remove the magazine by rocking it backwards. This was in no way ideal, and lacking proper materials I made do with what I had on hand. This worked well enough, so mission accomplished!

I'm so very much looking forward to returning to the field, so wish me luck on my recovery. I already have a new E&L AK stashed away for just that moment. I'll be doing some work on it in the near future, so stay tuned and play safe!

Plates On The Cheap

New plate carrier vests often come with some sort of foam inserts to hold the vest in shape. They're usually not very tough or rigid though, so the illusion of a ceramic plate isn't really there. To fix this, you can always buy ready made dummy plates, but what if you are on a budget? Then this quick guide is just for you.

If you happen to have an IKEA nearby, you can source some plate materials very cheaply. The LEGITIM series cutting board just so happens to have measurements that closely match the Medium SAPI plate (24 x 32 cm for SAPI plate, 24 x 34 cm for the cutting board). The thickness of a single board is about half of a ceramic plate.

The tools you'll need are a saw, a straightedge and a file or some sand paper (possibly glue). If you want to get fancy, a hot air gun or some hot water may also be in order.

To begin, take a straightedge and mark the corners of the board for cutting (the angle is about 45 degrees), or follow the shape of the foam insert that came with your vest.

Next, simply saw off the corners, and finish by either filing or sanding down any rough edges so they don't scratch and tear the inside of your vest.

If you want to get fancy, you can use a hot air gun or some hot water and bend the board to get a curved plate. Use a form, such as a piece of pipe or similar to get a symmetrical shape (I'm doing simple straight ones here).

Glue two boards together for a thicker plate, or put the board in front and the foam insert on the back for a more comfortable wear.

You'll be ready to operate in no time.

Let me know in the comments how yours turned out!