I recently acquired my very own FN303. As this has been a desire of mine for a long time, when Benji on PBN had a lot of them for a decent price, I jumped on it. Like everyone else says, finding mags is a pain, but I believe the marker to be worth it.
In this new endeavor, I'm going to eventually try some mods I haven't seen before and will post them here as I get the chance, but wanted to bring all the info I could about this marker into one place for anyone else who might be looking. I will provide links to original threads, but will try to pull pics over to host here as you never know how long a 3rd party host will last. And I'll copy the pertinent information over in case other threads get lost or moved.
Also, I need to give a special word of thanks to uv_halo, cougar20th, and tymcneer. These guys have answered multiple messages and graciously helped fill in info that wasn't readily available in the forum posts.
On to the good stuff:
Cougar's PBN on the FN303 is by far the most informative in letting a newbie know what they're getting into.
But this MCB thread is your starting place for paintball modding an FN303.
To get your FN down to legal field velocities, you have two options: devolumizing the dump chamber or lowering the operating pressure.
crzypntbllr includes the following great photos of cutting open the valve and of installing the spacers if you decide to go the devolumizing route.
The important info is to use a 3/0 jewler's blade to make the valve cut because if you cut too much of the valve material, you end up needing to shorten the powertube spacer as Simon explains here.
A starting point for your filler material is 4 thicker, nylon washers with an OD of 7/8" and an ID of 3/4" and one thinner, nylon washer with a smaller OD, but same 3/4" ID. crzypntbllr says that the center, long spacer in the photos is unnecessary and to leave that out.
For those cautious about cutting open their valves, there is the option of lowering the operating pressure.
Vitamin J on that same thread gives basic info on changing out reg spring packs. He used a newer-style automag spring pack and changed out the bolt spring for a shorter lvl10 gold spring. This is necessary because the stock bolt spring is too strong with less chamber pressure. I heard about this possibility elsewhere, but there are dangers of using a shorter spring and there are better options.
From Ty and Halo, I learned about using an AA raptor spring pack and readjusting it for lower pressure. The good thing about the raptor pack is that it is longer and so leaves you with a wider range of adjustment than Vitamin J's version. Note that the spring pack needs to be repacked from a "(())(())(())" high-pressure pack to a "()()()()()()" low-pressure pack. Also, Ty uses the main spring from an AXE to maintain the bolt spring length.
The FN303 uses cocker-threaded barrels, but the lead is shorter than a normal barrel (meaning if you screw a normal barrel in all the way, it will protrude into the breech). If you want to use a non-stock barrel (like the lapco or hammerhead FSR barrels), you need some sort of spacer. Cougar got away with using a large, thick o-ring, but woda on PBN made an aluminum spacer for this purpose. It's dimensions are 1.125" OD X .094" ID X .085" width, but the OD is not critical. Simon does not give the dimensions of his spacer, but here is a photo of it.
and VooDooAddict claims that they have tests showing that long tips (like raincovers) on FSR barrels actually decrease accuracy. So maybe put those milsim sniper dreams away.
And once you have the marker all set, it's not a bad idea to get the mag tension lightened up so you have the choice of using FSR's or roundballs. Since the mags have constant pressure on the projectiles and are sprung to move hard, heavy, plastic and bismuth rounds; letting off a bit of pressure helps keep paint rounds from deforming in the mags before they're used.
Matts' posts on inception's forums give the best set of instructions, but unfortunately, I can't get any of his forum photos to load, so only have the few I could find from google.
Matts says:
I have taken a several [mags] apart and it gets a lot easier as you do several of them but respect for that spring straight from hell is needed at all times, the windup spring is the "Violent" part of the assembly, if ever you have the bad luck to have taken one apart and the center of the windup starts unraveling, step back and let it be for a second or two, it will come to a semi mixed up ball of sharp edge 1/4" wide steel windup spring.
*Do not mix and match parts of older and newer FN303 magazines, the mold tolerances over time have changes, some parts may fit together loosely others are too tight.
To put it back in / reassemble an uncontrolled unwound spring... (add chosen swear words here, multiply swear words, add salt to open sores, use hammer on fingers if none come to mind), the outer layer of the spring must be counter wound back into the plastic spool assembly. the curve of the spring needs to be reversed completely.
Tools needed: 2 pairs of strong hands to take turns holding the spring in while the other set of hands takes a break and alternate rolling the spring back in counter clockwise, no you wont get a video about that. I also considered not winding it back in and just taking a loss and using the mag parts as spares, its THAT hairy.
To disassemble them:
1-Take the window off, I did not need tools to do this on my older FN303 magazines but I needed a flat flat screw drive to gently pry open the tab so the window can be un-clamped from the rest of the mag.
2-Removing the PB/FSR "indexing wheel" from the windup spool holder, the one of the center side has a mushroom clamp style that needs to be pushed thru but before you attempt to do so, the "indexing wheel" needs to be removed from the windup spool holder because its holding the Mushroom clamp fully extended, I pushed mine out using a punch tool and carefully without moving the mushroom clamp and pushing within the "Y" in the middle of the magazine out while paying close attention and seeing that the Y is not all perfect and that the segments of the Y are different lenght's making it "keyed" for the assembly, not re-inserting it the right way will make it bind on itself and make the re-assembly a lot more difficult, I put a dot using a silver sharpie on one of the Y segment end to match it back in during re-assembly.
3-Once the "indexing wheel" is removed, the windup spool is exposed. you can turn it by hand and feel the tension on it, WOW, a PB shredder for sure.
The trick here is to slowly lift the edge where the stopper is at without removing the center from the assembly, pushing the center mushroom clamp inward maybe 1/16 to 1/8" this is to make it skip past the stopper and remove the tension from the system until it comes to a stop without hitting the stopper (I mark the spot using a silver sharpie, a simply pair of dots will do, where is stops as this is a part of the observation that will come in handy when reducing the tension). Then I continue to rotate it in the direction it was going maybe another 20 to 30 degrees to have the center of the spring looses grip with the center "6 tip sun" that holds the end of the spring in place while the spring is under tension, these tips on the center sun are the key to reducing the tension on the spring.
4-Prying that spool holder off requires some torque control from your hands, prying with a flat screw drive on the edge and pushing out the center mushroom clamp is what you need to do here carefully observing the spring end actually stays in the spool holder and not on the tip of the center sun tips. once its loosened, wiggle it out slowly, observing the inner part of the spring on the 6 tip center sun, once its out > HOLD THE SPRING in from both sides all the while verifying that its in and flat, do not drop on the floor, do not tap on the table, its a spring grenade.
5-Re-inserting the spring spool holder assembly onto the base of the magazine, this is where that marks done with a sharpie are useful, you want to reduce the tension by having the spring latch on a different tip of the 6 tip center sun, skipping 1 tip/teeth I believe is all I needed as they are spaced 60 degrees from each other, I approach the two assemblies together observing where the center spring tip lands and press in very partially because remember you got to wind it back past the stopper, then when its past the stopper press it together firmly, now feel the tension difference.
That's all for now. If you guys have anything more to add, please jump in. Again, none of what I've posted thus far is original to me; I'm just compiling it for anyone else who may be looking.
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Originally Posted by dano_____
