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Thread: Basic body to take FN303 magazines

  1. #11
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    Have you been reducing the tension on them? I think that with the right sort of jig, it could be done. I've just got no experience with that sort of thing. In retrospect it was hilarious to see the 'spring cap' get hurled across the room, putting a black dent into the drywall. I'm glad I learned that lesson in the apartment :P

  2. #12
    I will try to do a quick video on how I did it. I have taken a turn out of the spring tension and it seems to work really well. So far no dents in the walls or springs flying across the room.

  3. #13
    This is how I was going to latch the mag's into place. There would be a spring to the top left of the lever.

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  4. #14
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    THIS IS A DRAFT DOCUMENT ON HOW TO disassemble a FN303 magazine, it will be edited and pictures added.

    Good day,

    ---=== AT YOUR OWN RISK / I CAN'T RECOMMEND DOING THE FOLLOWING WORK ===---

    I have reduced the tension on an FN303 magazine, the first ones I did where challenging, welcome the unknown ... err ... right.

    UV Halo that it is risky to do so as they are a nightmare to put back together
    The process is a little hairy but you can do it if you are careful (very careful)
    Yes, I second those comments, I have taken a several apart since 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.

    I have yet to:
    -Test the actual tension of a stock FN303 magazine, all I know its that its too much for regular paint ...
    -Test the tension post unwind of a magazine and record tension by say ... round spacing,
    -Chart it out in Excel and observe flat spots on rounds vs time.
    -It works with FSR's yes... as it did before, its just more gentle on the rounds now.
    -Test with regular paint. (time permitting this April), but what I know as of now is that initial tension is GREATLY diminished.

    THIS IS A DRAFT DOCUMENT ON HOW TO disassemble a FN303 magazine, it will be edited and pictures added.
    Last edited by MATTS; 04-02-2015 at 12:39 PM.

  5. #15

  6. #16
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    FN303 XL L7 post lathe work
    IMG_20150705_140457 (Medium) (Small).jpg

    FN303 Mag in pieces:
    IMG_20150706_210925 (Medium) (Small).jpg

    Back side of round indexer with the spring cartridge inside
    IMG_20150706_211007 (Medium) (Small).jpg

    inside housing without indexer or spring cartridge
    IMG_20150706_211037 (Medium) (Small).jpg

    inside housing without indexer or spring cartridge w/tooth painted silver as this is one of the two possible ones (that one and the one above it at say 3o-clock) that can be used for regular paint and will not blend it all.
    IMG_20150706_211356 (Medium) (Small).jpg

    close up of spring
    IMG_20150706_211420 (Medium) (Small).jpg

    close up of opening of the magazine / or closing and showing the silver tooth that the end of the 90degree of the inside portion of the spring needs to latch on.
    IMG_20150706_211552 (Medium) (Small).jpg

    How much I push the center of the spring cartridge out (but not entirely) to ease the unwinding.
    IMG_20150706_211625 (Medium) (Small).jpg

    installed spring cartridge unloaded/without tension, it needs to be wound back further then the stop peg, counter clockwise.
    IMG_20150706_211632 (Medium) (Small).jpg

    Final resting position of the spring cartridge past the stop peg (once its past squeeze assembly together)
    IMG_20150706_211740 (Medium) (Small).jpg
    Last edited by MATTS; 07-07-2015 at 03:44 PM.

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