Doubling Your Range: The Flathop.

Discussion in 'Gun Building, Modifications & Repairs' started by Wingman703, Jul 26, 2014.

  1. Wingman703

    Wingman703 Moderator Staff Member Moderator

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    Whats that? You want to shoot farther then that crappy 100ft of stock gun range? You are tired of being outranged by Walmart springers? Want to unlock the sharpshooter inside you? Look no farther!

    First, what is a flathop and how does it work?
    Airsoft guns gain range due to a 'backspin' effect. A small rubber nub nicks the top of the BB, causing the top to decelerate, forcing the BB to spin. This pushes air under the BB, giving it lift, and more importantly, range.
    [​IMG]
    A stock hopup chamber applies hop via a rubber tube, running perpendicular to the barrel, and a soft rubber cylinder that contacts the BB(bucking). While this works, it is not the most effective way of applying hop. What the flathop does is lengthen the amount of time that the BB contacts the hop nub/bucking. Much like rubbing your arm down a wall for 10ft would be harder then dragging it for 3ft, the longer hopup applies more hop, and more range. Like most hopup mods, this works best with heavier BB's. .25's-.30's are the 'sweet spot' imho for a stock gun that has been flathopped. Lighter doesn't allow as much spin to be applied, heavier BB's start to lose range due to the sub 400FPS.

    Now that you have somewhat of an idea the principles behind this, its time to show you how to flathop your gun.
    *NOTE*
    The flathop will work best when also used in conjunction with the mods found in the teching and mods section. Compression and consistency are some of the major factors affecting your accuracy and range.

    First, dissemble your barrel group into these three parts: Hopup, Bucking, and Barrel.
    [​IMG]
    First, we will work on the Bucking, the hardest and most extensive part.
    Take your bucking and gently turn it inside out. There are a multitude of ways to do this, I like the pliers method best. Rubbing a *small* amount of grease on the OUTSIDE of the bucking will ease this process. Above all, do NOT tear the bucking.
    Insert your pliers on the opposite side of the lips, and gently but firmly grasp said lips. The slowly pull the lips down inside the bucking. Take it slowly and carefully, easing it down.
    [​IMG]

    Once you have done that, there are two areas we will grace with our attention. First is the hopup's "bump" built into most buckings:
    [​IMG]
    Second is the "line" built into all buckings.
    [​IMG]

    Now, we want to remove both of these, and make them flush with the rest of the bucking. Depending on your level of patience, you can use sandpaper(high patience) dremels(medium patience) or a sharp object like a knife or scissors(low patience). Be wary however, the faster you go, the more the chance of tearing the bucking.
    Regardless of the method, I have found that its easiest when the bucking is supported by the barrel. I use an extra barrel cut down to length, but you can also use the exit end of your own barrel, like so:
    [​IMG]

    Now here is how you want the 'bump' to look once you finish sanding/cutting it away. You do NOT need to get it perfectly smooth. It only needs to be flush with the rest of the barrel.
    [​IMG]

    Flip the bucking over and do the same to the 'line'. Again, perfectly smooth is not a must, just flush with the rest of the bucking.
    [​IMG]

    Once these have been done, you can invert your bucking to its right-side-out position.
    When looking down the bucking, it should be smooth on all sides. The bump on the right of this one is a tear, not a bump(used older bucking for guide).
    [​IMG]
     
    Last edited: Jul 26, 2014
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  2. Wingman703

    Wingman703 Moderator Staff Member Moderator

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    Part two, hopup mods needed.

    Now that you have your bucking prepped and ready, its time to build the real magic of the flathop, the nub.

    Disassemble your hopup. Different hopups are different, none are hard to take apart. This is the M4 style hopup I am using:
    [​IMG]

    What you are after is the hopup arm. Again, M4 style arm/nub:
    [​IMG]
    See that tube of rubber? That is what WAS applying hopup to your BB's. Throw it away, or keep it as a souvenir.

    Now, for this next part, there are many different materials you can use. Eraser rubber, 70D Sorbo pads, rubber washers, I have even seen people use foam. You just need something with a flat and smooth surface that can be cut/sanded, and is slight squishy.
    Here, I will be using my current favorite, a scrap piece of sorbo pad.
    [​IMG]

    You will need to cut it to the length of your hopup window, like so. Side smoothness does not matter, the only side that must be PERFECTLY flat/smooth is the one that will press down and make contact with the bucking.
    [​IMG]
    Here, this is much to tall. Cut/sand it down to about half of that. Leaving it too big will cause BB's to always overhop, or jam if its waaay to big. Sanding it too small will not allow any hop to be applied, regardless of hopup setting. Best way to know is to test, simple as that.

    Once the nub is ready, we will turn our attention to the hopup arm.
    [​IMG]
    See that half circle that used to hold your nub? Yeah, that has to go, otherwise the nub will not bind properly/be inconstant. Cut/sand/dremel it down till it looks like this:
    [​IMG]

    Remember, this must be perfectly flat, not tilted to one side or the other. If it is tilted, it will give your BB's a 'hook' to one side or the other, where more hop is applied then the other side of the BB.

    Take your nub and glue it to the arm. I find superglue works best, as it quickly dries and doesn't need a ton of strength. Plus, you don't have to wait for 24hrs.
    If you are really nickpicky like me, you can wait till now to sand down the nub. This will allow you to get it perfectly flat and smooth.
    Unsanded to height, but attached to arm:
    [​IMG]

    Now, the final steps, putting everything back together.

    Remember that 'line' we removed? That needs to be rotated 90degrees to the barrel. Here, I cut a 'V' to show where the 'line' was on the barrel:
    [​IMG]

    And here is where it needs to be rotated too.
    [​IMG]

    This allows the BB to contact a fresh patch of the bucking, not one that has been worked over by your knife and is still rough.
    I HIGHLY recommend doing the floss mod found midway down the "My Guide To Fine Tuning Your Hopup" in the gun building & mods section.
    It will not only improve your compression, but it will also keep the bucking from rotating when it shouldn't now that the 'line' is gone.

    Now just reassemble everything and test. If you overhop no matter the setting, sand down the nub some. If the shots are flying everywhere, then re-sand/smooth your nub.

    When done properly and comboed with .30's, this should bring you around 200ft. After doing this ALOT and testing many different things, I can hit close to 270ft with it.

    This is the most basic way of doing it, what is listed is just getting you started. There are many ways to improve the basic way, difference combos of buckings and nubs, and many other things. Experiment and test, find what works and what doesn't, push the boundaries, and LEARN!

    Thanks for look'in.
     
    Last edited: Jul 26, 2014
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  3. Main_Stream

    Main_Stream New Member

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    Wonderful guide. Definitely needs to be stickied!!
     
  4. CollinC

    CollinC Active Member

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    Aaaand I knew all this yet my flathopping is crap. I jsut use the lazy man's Maple Leaf bucking. Was both your AKs flathopped today? Mine actually was pretty clsoe to yours in range with the 50 degree Maple and 340 FPS. Funny.
     
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  5. Wingman703

    Wingman703 Moderator Staff Member Moderator

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    Yes, I flathop all my guns. Maple Leaf works, but its also like $20, compared to scrap stuff and an hour for doing it manually.
     
    Evan J Johnston likes this.
  6. NoMoreRiots

    NoMoreRiots New Member

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    Awesome guide, deserves a sticky


    --NMR
     
  7. natethegreat

    natethegreat New Member

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    Wow... This is going to help a lot!
    Is the "goal" to make the flat hop nub as big as you can without making it squeeze into the barrel window?

    Build the best dont buy the best
     
    Last edited: Jul 26, 2014
  8. Wingman703

    Wingman703 Moderator Staff Member Moderator

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    Edited for spelling, grammar, and minor corrections, a nub hitting the top of the BB does not cause it to accelerate, but decelerate -.-
     
  9. Airborne101

    Airborne101 Well-Known Member

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    Yes. The longer the contact the bb has with the hop up, the farther it will fly/heavier rounds can be used. However, that is not to say that a hop up the length of your barrel would be good. There is such thing as too long, but since we aren't talking about modifying barrel windows, we don't need to worry about it.

    However, when making the nub as long as possible, be careful so as not to pinch the bucking on the leading and trailing edges of the barrel window, as that will cause the bucking to rip. So, make your nub smaller than the barrel window.
     
  10. Zardichar

    Zardichar New Member Supporting Member

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    Didn't star folder already make a guide on flat hop?
     
  11. Wingman703

    Wingman703 Moderator Staff Member Moderator

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    I didn't see one in here... that's why I made it. I couldn't find anywhere to point people to when they asked about it.
     
  12. nucklehead

    nucklehead Active Member

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    Nice guide, but I'm 90% sure someone has made a flathop guide, so doubt this will be stickied. Good job nonetheless.
     
  13. Wingman703

    Wingman703 Moderator Staff Member Moderator

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    I found a guide on ASF, but its broken over several threads and doesn't show the making of the nubs itself, unless I'm missing something. I have looked for some time for one place to point people to so I don't have to give them a half-answer when they ask what it is and how to do it.
    If someone does have a link to Star showing how to do it, I'm all eyes to see what the creator says about doing it.
     
  14. Airborne101

    Airborne101 Well-Known Member

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  15. Main_Stream

    Main_Stream New Member

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    I've read both guides. I like Wingman's better. It was easier for me to follow personally.
     
  16. Airborne101

    Airborne101 Well-Known Member

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    The thread I linked wasn't necessarily meant to be a guide, but rather a discussion and experimentation thread. That thread was created back when airsoft was largely rediscovering the Flat hop and it was becoming more mainstream. So there was a lot of discussion about what would and would not work well.

    For instance, Star_folder found that the M-nub and sorbo wasn't as good as some other nub materials.
     
  17. darkguy504

    darkguy504 New Member

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    Subbing! Great guide!
     
  18. ExtremMilSimOP

    ExtremMilSimOP New Member

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    I'm currently attempting to flat-hop my TM G3. De-nubbing the bucking was easy enough, but I'm having a lot of difficulty shaping my Sorbo (hop nub) to the proper size and height; it doesn't like to slice straight, and gives enough to slant all of my cuts (with a new razor blade mind you.) I've tried 220G sand paper to no avail, as it really tore the Sorbo before smoothing it over.

    How do you guys go about getting that perfectly flat surface on the top and bottom? I've tried Sorbo and eraser so far, and neither really likes to be sanded flat as far as I can tell.
     
  19. darkguy504

    darkguy504 New Member

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    Dude! I have been trying for hours on my JG G3! I cant shape the sorbo at all! Try putting the sorbo in a vice. Just dont over squish it.

    It does act like it dosent want to sand though. Hmmmm....
     
  20. NSW-DoubleTap

    NSW-DoubleTap New Member

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    Have you tried cutting the sorbo with scissors? Granted its not as precise, but you have 2 *blades* instead of a single razor which might help in cutting the sorbo in straight cuts..