I've seen a couple other people put markers inside an FN P90 shell to make an alternative scenario marker to the ones already available (typically either an AR-15 or an XM8 [SP8 namesake]). Personally I'm not a huge fan of mil-sim markers but I can appreciate them in their context. In terms of my marker selection, I chose the P90 mainly because it's unique in the paintball marker scene, since no companies sell direct P90 look-alikes or P90 aesthetics kits. I'm a fan of the P90 firearm's design, notably the Bullpup shape, horizontal parallel magazine, downward shell ejection, and the unique handling points which make it a compact and maneuverable firearm.
The conversion/installation for this mod wasn't especially difficult, but did take a lot of time consuming grunt work (mainly, to mill out the inside of the plastic shells). I've divided it up into the literal work periods that I underwent whilst making this marker (one each day, for several days).
Conception:
I chose to modify an Ion for this project, due to Ions' extremely segmented nature. All parts of the gun are linked by hoses, which are the perfect methods to create a custom project. Additionally, as with my other Ion projects, I have a number of Ion parts available already so it won't be hard to scrounge parts to create what I need.
The plan is this. Take an Ion firing assembly and mount it inside the emptied P90 shell. The barrel will be removeable so I can install virtually any barrel I wish. Inside the P90 shell I will mount a regulator (likely a standard vertical reg), which will attach to the fire chamber using 4-mm tubing, and also attach to the solenoid using 1/8" tubing. I'll use something other than an Ion solenoid with this, since I have others available. Also, I'll use a board from another gun (or one I make myself) since, again, I have things available already.
The two large silver "cylinders" visible inside the airgun are actually just metal weights, to make the assembly heavier. The rest of the airgun consists of the propellant motor toward the rear (a motor spins which actuates a cam-activated piston, firing the BB rounds), the long barrel, and the trigger/safety components toward the front. Most of these items were removed at this stage.
Day 1:
The first step is to physically allow the Ion firing assembly and barrel to fit inside the shells. This was accomplished by milling out the internal ridges that are in place for plastic stability. This was easy, but took a while to finish (and there were naturally a lot of plastic shavings all over the place afterwards).
· With the Ion body in place, I drilled and tapped some holes in the breech around the barrel, and also in the swivel donut at the rear, afterwards drilled opposing holes in the outside of the shell pieces. These screw holes will be used to mount the firing assembly in position within the P90 shell.
· I have to mount the regulator and solenoid inside the marker, so this was the time to plan it out. For this mod I'll be using a Parker K4H04 solenoid (used in Intimidators, similar valves used in SP markers) which is a barb/threaded four-way solenoid that I will convert into a three-way by plugging one of the output ports. The regulator I will use for this project is a CP reg. The main reason why I chose this was because it's adjusted by sticking an allen wrench into the side of the reg, so all I will have to do is mount the reg inside the marker and drill an opposing hole to allow access to the pressure adjustment screw. I took a standard ASA tank adapter and milled off most of the unused portion, then drilled and tapped both the ASA adapter and the CP reg for air fittings. One will be used for the fire chamber and the other will be used for the solenoid.
· The air source will attach to the reg via macroline which will act as a remote line to a tank on my back. I'd like to mount an ASA onto the marker but there aren't any easy ways to do that without reinforcing a large area of the shell insides (since the plastic couldn't take the weight of a tank attached to it, without also reinforcing it).
· At this point much of the work was complete. Here's a picture.
Day 2:
This was the electronics installation day. For the mod I decided to use a DM4/5 circuit board with upgraded chip. These are easy to find and will have all the functions I need, so it's what I chose. As for mounting it inside the marker...there are lot of possibilities, but I ended up choosing to mount it on the inside of the rear "plate" at the back of the shells. This plate has a small latch and can fold downward to access the inside, which will work perfect for battery and such.
· The board is mounted vertically to the rear plate, with battery directly in front of it. I drilled a hole in the rear plate to view the DM4 board's LED, for programming and board status.
· The powerswitch to turn the marker on and off is located in front of the rear plate, on the side of one of the internal "ridges" for stability. I put the switch(button) here so it would be out of sight. I didn't want to put it on the outside of the marker unless it was inconspicuous, but I didn't happen to have any inconspicuous switches in the workshop at the moment (and didn't want to wait a week after ordering one) so I just went with this method instead. In the picture below, the red push-button switch is the powerswitch (orange wires connect it to the DM4 board).
· For the trigger microswitch, the P90 airsoft internals made use of a switch of their own, so I'll just re-use that. No reason to overcomplicate things by adding my own parts when they're not required. I soldered wires to the existing switch (blue wires) and attached them to the board.
· Attached a pair of wires to the solenoid (red).
· I didn't install eyes in the marker at this point. I'll install those later if I want to put them in. They're not required so I'll wait until I have the whole thing up and working.
· Lastly, had to mount a steel pin for the trigger, since I inadvertently removed the ridges upon which the trigger slides. I had to add this steel pin so the trigger wouldn't pop up out of position when pulled (the steel pin isn't visible in the below pic).
Day 3:
Minor work here and there, put everything together, and tested it out.
The hole on the left side of the stock is for an input pressure gauge, which I never installed (plugged it instead). I'll put one on there later if I feel the need.
Performance / Addendum:
Just a couple quick notes here after I've used the marker on the field. The first thing is that it's very different to hold this type of gun shape, compared to a regular paintball marker. The tank on a typical marker makes it easy to steady the whole platform against your shoulder...the P90 doesn't have anything like this unless you "chicken-wing" it by sticking your elbow out. That gives you a mich wider profile to get hit so I always avoid that (also makes you look like you're playing a war-game...not my intention here).
I took the P90 Ion out to the field a few times during the Tippmann World Challenge 2007 game, but we don't have any actual action footage of it. I can be seen holding the marker for a brief second, just before getting shot out and leaving, at the beginning of the first video clip:
Tippmann/World Challenge 2007 videos (video at the bottom of the page)
Balance issues aside, it's pretty fun to use. There isn't a lot of recoil since the maker is quite a bit larger and easier to steady, even when "hip shooting" which I became fond of doing pretty quickly. I had the setup set to 10-bps ramping which did the job good.
Many people asked me (after hearing it was an Ion internally) how they could obtain a similar mod, so I might consider offering this as a service in the future. We'll see...
I hope to use this again next time I make it to a scenario game or perhaps even a backyard play.