My guide to fine tuning a Hop-Up

Discussion in 'Gun Building, Modifications & Repairs' started by Tackett, Oct 11, 2011.

  1. Tackett

    Tackett New Member

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    So, I'm seeing a lot of threads on subjects like: "what 750mm barrel will give me the most accuracy." and so forth.

    The real sad part to these questions is, that typically the person asking is putting this brand new $60 plus barrel into a totally stock hop up assembly. This is not the way to improve your accuracy or range. The first and very first thing a person should be doing before turning to the barrel, is fine tuning the hop-up. Only after the hop is tuned should you even consider turning to the inner barrel. If someone is unhappy with their AEGs accuracy, my advice is always to tune the hop-up, use the gun for a while, if you are unhappy with the performance still, then start turning your attention to the inner barrel or other items. So this guide is being written to serve as a starting point for those wanting to increase their accuracy.

    Step 1: organize your workspace.
    Before starting on any project, always start with a neat, clean, organized, workspace. Place down a towel to keep the small parts from rolling around. Like so:
    [​IMG]

    Step 2: organize your tools.
    You will need:
    A naked utility knife blade.
    A small sheet of aluminum foil
    Superglue
    A dremel with cone grinder attachment
    Dental floss
    Teflon tape
    Permatex anaerobic gasket maker.
    Lube of some kind
    A solid nub. (SCS, hnub, or even a piece of wire.)
    A standard squishy nub

    Step 3: Prepare the Bucking
    Now, why exactly are we messing with the bucking? Simple, consistency and shape. There is one thing on the inside of these buckings that will, overtime, lead to a inconsistent hop up. A little mound of rubber. To get to this thing, you have to turn the bucking inside out. Now, most of the time, that's easier said than done. Especially with the softer buckings that will tear if you aren't careful. The easiest way to do this is to use your inner barrel and unroll it. It doesn't matter how you do it, just flip it inside out, unharmed.
    [​IMG]

    See the little mound now? We need to get rid of this thing. There are a number of ways, I use a dremel, because patience is not one of my virtues. But however you do it, be careful and sand it down out of existence. It should look like so:
    [​IMG]

    Well, we are left with a uneven surface that's been roughed up by our removal process. We need a nice clean surface to make contact with the BB. We can achieve this by removing the locking line, much the same way that we removed the mound. Very carefully. It should look like so:
    BEFORE
    [​IMG]

    AFTER
    [​IMG]

    Next we need to cut off about 5mm or more off the end of the bucking. We do this because when we go to seal it, the added material of floss and tape will stretch out the bucking, and make it impossible to get the c-clamp on. Use your naked blade, and chop it like so:
    [​IMG]

    Now, use your blade and slice a small V at the end of the bucking, pointing at the clean area we want the BB to contact. This is so, when we turn the bucking right side out, you can tell which side is up.
    [​IMG]

    Turn the bucking slightly right side out, except for the last 1/4 of it. Like so:
    Your bucking is now tuned and ready for install.
    [​IMG]
     
    Last edited: Oct 17, 2011
  2. Tackett

    Tackett New Member

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    Step 4: install the Bucking
    We are going to be installing the bucking in a way that there is no possibility of a air leak anywhere. The first thing you want to do, is run a small bead of permatex around the end of the barrel, between the nozzle side and the hop window. Like so:
    [​IMG]

    And after the hop window, like so:
    [​IMG]

    Place the bucking on being very careful not to smear the bead of permatex, making sure your V notch points at the hop window. So you know your good section of rubber is where it needs to be.
    [​IMG]

    Unroll the rest of the bucking, again, being careful not to smear the permatex all over the place.
    [​IMG]

    Now, take a small length of dental floss and make a loop on the end:
    [​IMG]

    Wrap the rest of the floss over the bucking pulling it tightly. Thread the tag end through the loop and pull the other tag end so that the loose end gets pulled under the tightly wrapped floss.
    [​IMG]
    [​IMG]

    Cut the loose ends. The finish product should look like so:
    [​IMG]

    Now, I always wrap a small amount of Teflon tape tightly around the end, being careful not to cover up the indents for the clamp to seat in. Usually two turns is all I do. Finished bucking should look like this:
    [​IMG]
     

  3. Tackett

    Tackett New Member

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    Step 5: install the Chamber

    This part is tricky. Use copious amounts of lube and slowly, carefully twist the chamber over the bucking, making sure you end up with the "V" pointed at the location your hop arm is going to go. Make sure it doesnt wrinkle up, and gets installed correctly. You should end up with a finished product like so:
    [​IMG]

    This part takes time, and if you have too much floss and tape on the end of your bucking, it will make it even harder, if not impossible. So if at first you don't succeed, try try again. Keep at it, start over if you have to. It's not easy, but it will go. I promise.

    Step 6: Tune the hop arm
    Where we removed the internal mound, we need to backspace the nub to make up the difference. I do it this way, but it doesn't matter how you do it.

    Take a standard squishy nub, and slice it a little over halfway with your razor.
    [​IMG]

    Put a dab of superglue on the hop arm and glue the little slice of stock nub to the arm:
    [​IMG]

    Now take your solid nub, whatever the case may be, (In this case it's a SCS.) and glue it to the stock rubber that's glued to the arm, like this:
    [​IMG]

    Let this thoroughly dry. You may have to shave the ends off slightly so that the arm articulates smoothly.

    Now, with many hop ups, the adjustment dial is extremely loose. To the point that, the bbs hitting the nub, can actually through your adjustment off. Let's fix that by shimming the arm, so it fits tightly into the chamber and is not so easily moved. This will allow finer adjustments, and keep it from being inadvertently thrown off.

    Take a small piece if aluminum foil, spread some super glue on it, and press the hop arm against it.
    [​IMG]

    Let the glue dry and slowly peel off the excess foil.
    [​IMG]

    Install the arm and turn the dial, keep adding layers to the arm until you get the tightness desired. I like mine so tight that I have to turn the dial with a pair of needlenose.


    Step 7: Final adjustments
    Now that everything is installed, look inside the barrel with the hop fully on and make sure that the nub is centered in the barrel. If it is not, twist the barrel holding the hop chamber steady, until the nub is centered correctly.

    Run a bead of superglue around the barrel and end of the hop chamber. Then ram home the brass collar.

    Finished:
    [​IMG]

    Now, your hop chamber is about as fine tuned as you will get it, and doing this mod correctly will enable you to squeeze every last inch of range and accuracy as possible with a semi-stock chamber. If this does not satisfy you, then it's time to start down other avenues such as swapping barrels
     
  4. Airsofter5050

    Airsofter5050 New Member

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    Wow great job :) did it improve the accuracy much?
     
  5. Robin-Hood

    Robin-Hood Active Member

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    Good job Tackett. I deleted your double post of the final steps cause I didn't see any variation so figured it was an accident.
     
  6. Tackett

    Tackett New Member

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    It Was. I was trying to get around the 10 picture limit and still maintain cohesiveness. Thanks pal.

    @airsofter5050
    You'd be surprised how many people ignore the hop up entirely, thinking that cramming a uber long tbb into a stock assembly is going to give them the results they are looking for.

    I always advocate tuning the hop up like this, before changing barrels.
     
  7. Airsofter5050

    Airsofter5050 New Member

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    I know they think a 509mm 6.01 barrel will have extreme accuracy.
     
    edmundo.tiao likes this.
  8. Adman234

    Adman234 Active Member

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    Wildwood
    Awesome guide. This is what I do. I really like the idea of cutting the notch to know which way is up, and also using the plastic tube inside the bucking to give it support while cutting. This will vastly help me. Shows that even I can learn a few things :) I also like your method of arm-shimming. Really good idea, but I must ask: does the foil wear off?

    Now a few critiques:

    IME it is best to get a tiny dab of permatex (about the size of a nub) and smear it all over the inner barrel, where the bucking goes, rather then put it on in a ring and then slide it on. Better even distribution. And then when the bucking slides all the way on, you can wipe off any excess.

    Also, make sure that you don't get any permatex into the hop-window. With friction when it dries, even a tiny piece coming off into the barrel can gum up the inner barrel.

    I also recommend to let the permatexed bucking dry for at least a day, to make it easier to insert into the inner barrel.



    BTW, what brand is that bucking? I know that you have been testing many brands lately.

    Awesome writeup bro. I always tell myself to do these, but I get lazy and never get around to actually making the thread. I vote that this gets a sticky, or at least make a thread like on ASF that has lots of different guides linked from it. We should do that.
     
  9. jonnyboiii

    jonnyboiii New Member

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    I agree. ....20 freakin characters.
     
  10. RCV

    RCV New Member

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    Phenomenal Tackett. Great job. I learned a couple tips that's for sure...i would be angrily surprised if this does not get a sticky
     
  11. Tackett

    Tackett New Member

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    Thanks for the critique buddy. I never thought of either smearing the permatex like that, but it makes sense it would be a better seal.

    I forgot to mention about the hop-window, but that is excellent advice. That's the reason for unrolling the bucking rather than sliding it on. And waiting on it to dry is also a excellent idea as well.

    The bucking is actually, I believe the last bucking I have to try other than the prometheous ultra hard, and the king arms 80D (which is going in the DMR soon.) the SHS white bucking. And review wise for it, I was actually underimpressed with the structure. There was a lot of flashing that needed cut off, and it is very thin for my tastes. (though, depending on your application needs, could be good.). We will see how it performs.

    The tin foil doesn't wear off, or at least, hasn't yet. I've used this method of shimming for a while, and have found no real ill effects from it. Though any method if shiming will do as long as it gets done.


    I really made this because I realized that I kept preaching to people that they needed to fine tune their existing setup before making judgements on it's downfalls, and I never told them how. So hopefully this will help some people who were pretty much in the dark about aeg hop-up assemblies needing anything done to them in the first place, squeeze a little extra out of it.
     
  12. Adman234

    Adman234 Active Member

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    Wildwood
    Yeah, no kidding. People ask too often how to increase accuracy, and now we can link them to this helpful guide instead of just saying, "R-hop, systema bucking, SCS, Prometheus TBB".

    Glad to see this get stickied.
     
  13. Tackett

    Tackett New Member

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    If anyone wants to know.....I am amazed with this bucking.

    Though granted, it's in a low fps gun, it's seems to really grip the rounds. They have more significant backspin than the other three buckings I tried in different mutations of this gun. The nozzle is sealing with no problems at all, and the thinness (is that a word?) seems to really help the ammunition feed. I said before that there was some flashings that needed cut off, and that's still true. It's possible I received a bad apple. I'd have to order more to find out if it's a poduction problem or not. This is probably the thinnest bucking I have seen yet, and seems pretty sturdy. It takes quite a bit if force to shear it , even with the razor. The thickness makes me wonder about longevity, it will take some time before I have that answer. So far, as with the rest of SHS products, great product so far. I'm pretty shocked.

    I need to sit down and write a review of all these buckings and rate them on different categories from 1-10...
     
  14. jonnyboiii

    jonnyboiii New Member

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    Will the new contact point of the bb be on a completely seperate part from the two that are sanded down? Like in between the mound and the locking line?

    And which half of the cut nub do you use?
     
    Last edited: Nov 19, 2011
  15. Rifled-n-Ready

    Rifled-n-Ready Active Member

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    Very nice tackett!!! Somehow this guide has avoided me till now, i feel like a mini tackett tho i did all this on my own just making it up as i when, too bad it didn't solve my accuracy issues and i still need a barrel, oh well
     
  16. jonnyboiii

    jonnyboiii New Member

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    Since Tackett's out, can someone else answer my question?
     
  17. Adman234

    Adman234 Active Member

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    Johnny, yes. You need to rotate the bucking 90 degees so that it has a completely flat surface to engage.

    And if you cut the nub in half, then I don't see why either one would be different. Either side is fine.
     
  18. Tackett

    Tackett New Member

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    Whoops, apologies my friend. I seem to skim by people's responses in the sticky section for one reason or another.

    But Adam is correct, you want your notch pointed a place on the bucking untouched by your sanding. So you sand the lock line off, sand the mound off, and cut your notch pointing at the good section of the bucking that still has the factory surface. Install the bucking with the notch pointing at your hop-window.

    And it doesn't matter if you space the nub on the arm with feces, as long as it gets spaced. Either side of the nub will work. I use a standard nub, as illustrated in this guide, because I find it to be the perfect thickness and has given me the quickest result.
     
  19. levirocks

    levirocks #FreeNuggy Lifetime Supporter

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    I'm feeling stupid but what mound are you talking about?
     
  20. Thunderbo15

    Thunderbo15 Active Member

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    The internal mound on the bucking lol

    And Tackett (which I had PM'd you about before), I've found that in my SCARs hop up, adding in the half nub seems to make it protrude way too far inside the hop up chamber, although I haven't done it on my AUGs hop up yet to compare. Has anyone else put the half nub in an AR hop up?
     
    Last edited: Nov 20, 2011