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Star_folder

Flat Hop (Necro Exempt)

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Rather than re-type the explanation I'll just steal a quote from myself on AM:

 

Wow it looks like everyone really wanted steel ammo........ Roll Eyes Tongue Maybe thats a good thing.

 

anyway I'm casually looking for the next real project. Failing that something else has become apparent to me recently: its hard to get a good aftermarket nub. I could go the route of casting them in small batches, but that would seem to drive the price up since individual castings take some work to do and how much do you really want to pay for a piece of rubber so small you could sneeze and lose it. I could surf up an item number for the correct thickness and durometer rubber and publish it, but nobody will want to pay commercial shipping and meet the minimum order quantity just to cut a few infinitesimally small squares out of it. And so that thought train has lead me to where I am now. Would people have any interest in having me supply small squares of rubber which could be piggybacked on things like R-hop orders to cut your own nubs from? The process would be super simple, just cut it to the right size square, modify your hop arm to be flat, and drop it in. It'd be soft, thermally stable, and broadly applicable. It'd also cater to the DIY crowd which I prefer to the drop in newbies crowd. The question is would people find this to be a helpful service? I'm thinking something like 3$ for enough to make, I don't know, five or more of them? I would offer it with a mild adhesive backing so its both easier to cut and will adhere. Does anyone have any interest in something like this?

 

Ok typing this my idea congealed a little. It can come cut to length to match R-hops or ER-hops and just tack an extra 3$ for Rs and 4$ for ERs onto your order. Each piece would be enough to make about 8 nubs of a corresponding length to the R-hops you just ordered. In this way it'd be a cheap and easy way to get a nub with your R-hop which you could tailor to your specific application. Does this sound like something people would want? Its more of a convenience thing than anything else.

 

This isn't meant to be me hocking my products here, but more asking if anyone would have an interest in such a thing. In essence would it be helpful to have a better source of nub material than sorbo scraps? The adhesive backing would also make attaching your plastic super easy.

Edited by hunterseeker5

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Rather than re-type the explanation I'll just steal a quote from myself on AM:

 

 

 

This isn't meant to be me hocking my products here, but more asking if anyone would have an interest in such a thing. In essence would it be helpful to have a better source of nub material than sorbo scraps? The adhesive backing would also make attaching your plastic super easy.

 

Alright, and thanks to everyone for the earlier explanations of the plastic. I'm quite interested in this, being part of a semi- DIY group, yes, I'm all for tuning and such, making a nub doesn't scare me, but you get old, your hands start to shake, and it'll take me too damned long to assemble a sorbo/plastic/cut in half nub monstrosity on my own. Having something to cut out with adhesive already on it would make my life a lot eaisier, and therefore make me much more likely to do it.

 

 

*Warning - The following is typed as I think it, be prepared for still-developing ideas and general lack of coherency*

 

One thing I'm pretty interested in is Krap101's extended concave nub project, combined with a flat bucking, this seems to be a pretty great idea, as the one thing the SCS did really well with it's concave shape was allow the rubber to flex around the bb, uhm... kinda like this, if you imagine the red line as the SCS, the blue line as the bucking, and pretend the bb is in there pushing the bucking up:

 

___

/----\

 

See, the bucking flexes around the bb when your hopup is set it a way the the ends of the SCS are pusing down the bucking, but the bb doesn't actually reach all the way up and push the bucking into the scs, meaning that the bucking is being forced into a shape around the bb BY THE BB ITSELF, and as the bb travels through, hop starts gentle [bb isn't at it's widest point], and increases as the bb goes through, allowing acceleration in the spin direction. This, so long as you didn't have to turn your hop up higher, allowed the bb to essentially form it's own hop profile as it went through. So a concave nub that's extended to provide the advantages of flat hop could possibly rival the R-hop in performance, and would certainly be eaisier to install, only requiring a drop-in nub and a sanded/rotated bucking, allowing people who aren't into the level of DIY that the R-hop requires to break into this stuff. from a buisness standpoint alone, getting a product to all the people who were ready to jump on the customization ship for the SCS [since this will be essentially the same thing, so we can assume they'll be up for this too], would mean a lot more revenue than only pandering to the crowd who is ready and able to do the kind of work the R-hop requires. In fact, what I'm likely to do is buy one set of IR-hop rubbers and two sets of nub blanks, and do the extended SCS nub right away and shelf the R-hop stuff until I run into a bunch of spare time.

 

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Alright, and thanks to everyone for the earlier explanations of the plastic. I'm quite interested in this, being part of a semi- DIY group, yes, I'm all for tuning and such, making a nub doesn't scare me, but you get old, your hands start to shake, and it'll take me too damned long to assemble a sorbo/plastic/cut in half nub monstrosity on my own. Having something to cut out with adhesive already on it would make my life a lot eaisier, and therefore make me much more likely to do it.

 

 

*Warning - The following is typed as I think it, be prepared for still-developing ideas and general lack of coherency*

 

One thing I'm pretty interested in is Krap101's extended concave nub project, combined with a flat bucking, this seems to be a pretty great idea, as the one thing the SCS did really well with it's concave shape was allow the rubber to flex around the bb, uhm... kinda like this, if you imagine the red line as the SCS, the blue line as the bucking, and pretend the bb is in there pushing the bucking up:

 

___

/----\

 

See, the bucking flexes around the bb when your hopup is set it a way the the ends of the SCS are pusing down the bucking, but the bb doesn't actually reach all the way up and push the bucking into the scs, meaning that the bucking is being forced into a shape around the bb BY THE BB ITSELF, and as the bb travels through, hop starts gentle [bb isn't at it's widest point], and increases as the bb goes through, allowing acceleration in the spin direction. This, so long as you didn't have to turn your hop up higher, allowed the bb to essentially form it's own hop profile as it went through. So a concave nub that's extended to provide the advantages of flat hop could possibly rival the R-hop in performance, and would certainly be eaisier to install, only requiring a drop-in nub and a sanded/rotated bucking, allowing people who aren't into the level of DIY that the R-hop requires to break into this stuff. from a buisness standpoint alone, getting a product to all the people who were ready to jump on the customization ship for the SCS [since this will be essentially the same thing, so we can assume they'll be up for this too], would mean a lot more revenue than only pandering to the crowd who is ready and able to do the kind of work the R-hop requires. In fact, what I'm likely to do is buy one set of IR-hop rubbers and two sets of nub blanks, and do the extended SCS nub right away and shelf the R-hop stuff until I run into a bunch of spare time.

 

You know someone on AM JUST asked this question. Rather than type out another answer I'll just refer you to his question and my response. The summary though is you're not really going to get what Krap101 would call active concave, or a visibly concave surface which the bb fits into, and the theory of passive concave doesn't work because it'd require too much downward pressure on the bb and you'd get atrocious over-hop. Anyway here is the thread:

http://forums.airsoftmechanics.com/index.p...g55564#msg55564

 

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the theory of passive concave doesn't work because it'd require too much downward pressure on the bb and you'd get atrocious over-hop.

 

How much pressure do you think it actually takes to deform my nubs? We're not dealing with tire rubber here...

Edited by krap101

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How much pressure do you think it actually takes to deform my nubs? We're not dealing with tire rubber here...

The rest of the discussion that came from this comment can be found here:

http://www.airsoftforum.com/board/Concavity-t233931.html

 

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Woah, I got some new reading to do...

 

dang-it guys, I'm just an old guy who fixes guns, I made an account to ask one question, and within a week you've all turned me into a fourm-er.

 

But all this has left me confused, what would be the best way to go for a flat hop then? Firefly nub from overseas? Or have we found a better way?

Edited by Kelijareph

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Woah, I got some new reading to do...

 

dang-it guys, I'm just an old guy who fixes guns, I made an account to ask one question, and within a week you've all turned me into a fourm-er.

 

But all this has left me confused, what would be the best way to go for a flat hop then? Firefly nub from overseas? Or have we found a better way?

 

Mission Accomplished :D

 

Making a flat nub isn't very difficult. There are examples of peoples' attempts earlier in the thread. The firefly buffer is the "off the shelf" nub, but everybody is out of stock currently. Airsoftatlanta is probably the most likely to have them in stock, but they're quite rare. Then there are the other hops mentioned in the concavity thread

 

I'm guessing the easiest way to make your own nub is to buy some sorbothane from mcmaster and glue it to a cut up pen ink tube.

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Ok before we get into another discussion and this turns into a mess like last time I'd just like to say. ALL TROLLS SHUT THE :censored2: UP THE ADULTS ARE TALKING. If you can't say something intelligent and coherent don't say anything, I do NOT want a repeat of the AM thread which was a massive clusterfuck and demolished what was actually shaping up to be a productive discussion and drove Krap101 off AM. Krap if this does go to pot could we agree move it to PM so, while the community will forfeit the benefit of reading it, the discussion can continue in a reasonable fashion?

 

Yes the pictures are solely for illustration, it was just an observation. :P We're very visual creatures, so the pictures make a great descriptive crutch to "quantify" things by saying less or more than the example. No worries I didn't think the modeling was based on direct measurement and observation. Here is where we start to diverge though. My understanding of your first "argument" about passive versus active concave is that you get enhanced contact because the bb is being contacted, rather than along a "line" where it makes contact on a solid surface, but a hemisphere as it passes by. As you noted material recovery rate will affect how much a role this plays on the trailing edge of the bb, but the leading edge should experience it as pictured. (again in the broadest sense as a demonstration) The theory is then that rotational acceleration is improved because your area of contact is larger despite a shorter contact stroke? I guess I'm trying to understand what the thrust of your argument from your first two paragraphs is. My interpretation is that you're saying a concave contact, in essence more contact along the x and y axis only, does NOT improve accuracy, its based solely on the moment/torque being applied in precisely the same quantity. Right? You follow that up by saying "Consistency/accuracy is thereby affected by uniformity, finish and all that." Not disagreeing with that, but would that then suggest that the maximum overall surface contact between the bb and the bucking would be ideal. Whether that occurs in an active concave system or passive concave system is subject to debate because we've not measured properly :a-shocked: but is that the essence of what you're getting at? Maximum contact area, assuming identical finish consistencies etc, will produce the most accurate hop in your opinion?

 

Ok now let me throw a wrench in all that. The active concave system, the SCS (or big out H-nub if you prefer), did something interesting. What it produced was tighter groupings along the X-axis (this is on the target, just for clarity's sake) but skewed it along the Y-axis. We attribute this to bb diameter inconsistencies under a hop which is too hard, but there is that inescapable little data point which shows more contact along the X-Y axes (we're talking in the hop now) and a reduction of contact along the Z-axis improved ONE aspect of accuracy which I attribute to improvement of spin axis consistency. Maybe this is anecdotal, but it is in many ways the basis for the argument that improved concavity will improve accuracy along the X-axis.

 

We rather blithely refer to LRBs as if they were all the same. There are three distinct LRB types I'm aware of. The first is what we typically think of, its the bent barrel. The second is a barrel in which the outer barrel is straight, but the bore has a slight curve to it. The third, and perhaps most interesting, is a perfectly straight bore, but at the base of the barrel is a little "step" of sorts which initially kicks the bb to the ceiling of the barrel where it remains as spin is increasingly imparted to it and it slides/rolls down the ceiling of the barrel. The efficacy of these systems is subject to as much myth and lore as it is science in many respects because they're rare and, lets face it, under-hopped bbs are perceived as, and are, more accurate. So where does that leave us with the LRBs? You can say they have only one point of contact to spin the bb, but I'm not sure its really comparable. When you fire a bb through a rubber hop its sliding against both the rubber and the barrel below. The hop is in essence the "winning" of the friction of the rubber over the metal. The LRBs don't split friction forces between the top and bottom of the bb, the bb only contacts one. The rotational acceleration is also MUCH more gradual. That said some of the same mechanism occurs in our barrels as well since our bbs also roll/slide along the barrel ceiling so separating the effects is a bit problematic. I guess I'm not sure what to say about your mentioning of the LRB because I'm not sure exactly how you're using it in your argument or if its just an anecdote.

 

"More contact with the bb (I.e. concavity) is just another area to input error into the shot, but more contact is needed in order to hop heavier bb's (wider, longer, or wider and longer), and each concavity/hardness has to be matched with a range of hopup with the energy of the bb (mass and velocity)"

I guess its easy to take this to its logical extremes to demonstrate your point here.

 

I guess the one thing I'd bring up is the seeming strange phenomena of increased level flight with what I'll term "extended" hops which have a relatively smooth transition with the barrel. Don't know what causes this, or how, but it appears not to be concavity based on the examples you gave above.

 

I guess this has gone off topic enough for them to give us our own thread, so I'll reply here:

 

http://www.airsoftforum.com/board/Concavity-t233931.html

 

 

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Hey guys, I just I would let everyone know that I just updated the OP with this content:

 

 

I figured I would post a bit of an update, and try to compile some of the content of this thread into the OP, so that people don't have to read so much. After looking through it all, I couldn't decide what to pick. So my suggestion is to take this as a guide on how to flat hop your bucking, and then skim through the thread (or read through it if you are really interested) and make your own nub.

 

DSC00856.jpg

Your generic 2 piece M4 hop up, pulled out of a KWA SR-5.

 

DSC00858.jpg

Pull the barrel out, pull the bucking off the barrel. Taking the hop up apart is unnecessary, but I generally rebuild them whenever I work on them.

 

DSC00859.jpg

You'll need a pair of pliers, something shaped like these.

 

DSC00860.jpg

Stick the pliers in about like that. Then you are going to want to open the pliers a bit, and fold the bucking's lip into the grasp of the pliers

 

DSC00861.jpg

About like this.

 

DSC00862.jpg

Now you will carefully pull the bucking through itself using the pliers. You sort of slide it along. Be careful and don't go fast, you don't want to rip the bucking or damage it.

 

DSC00863.jpg

Ta'Da. An inside out bucking.

 

DSC00865.jpg

DSC00866.jpg

DSC00867.jpg

DSC00870.jpg

Then, using some sand paper, a dremel, nail clippers, your teeth (probably a bad idea) you'll want to remove the inner ridge (the first picture), and the inner mound (the third picture). I used to simply hold the bucking between my fingers, but others have had success slipping the bucking over the non hop up end of the barrel, so you have a hard surface to sand on. I used a dremel, so I didn't quite have to do that, but it is very helpful. Just be careful to not sand through the bucking. You also want to try and sand as little as possible of the insides of the bucking.

 

Then, wipe it clean, soap & water helps, and then flip it back right side out in the same way you flipped it inside out.

 

Alright, now put it back on your barrel. Generally I hold the bucking, and put the barrel in upside down, with the hop up window on the bottom. I do this so that I can see what the inside of the bucking looks like, and know that it's going to have a smooth part of the bucking that makes contact with the bb.

 

DSC00873.jpg

A bad contact patch.

 

DSC00874.jpg

A good contact patch.

 

See the difference, one is smooth, and that smooth part is what you want over your hop up window, not the rough side of the bucking.

 

And, for some help finding those particularly helpful threads on making nubs, here are some links to posts throughout this thread:

Kamikaz3 review of the flat hop

Starting at this page, and continuing to the next has lots of good pictures and ways people have made their nubs.

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I know I'm a bit late to the party but I figure I'd post my results.

 

Gun: g&p m16 vn

Fps: 398

Barrel: Madbull 6.03 mm

Bucking: systema (blue)

Nub: just a soft eraser glued to the hop up arm

 

All I had for the test were .25g golden balls.

 

I measured my target out to 75 yards (225 ft). Target was a plain sheet of paper.

 

On semi auto I was getting about a 3 inch grouping. On full auto it spread to about 1 foot (not sure why).

 

I must mention that it was pouring down raining. Not bad for about 10 minutes of work.

 

Once I get some .36g in I'll do another test.

Edited by proplayer187

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lol, yeah, you are a little late, but those are some great results. Especially in the rain.

 

And the reason full auto has a wider spread is because of the gun vibrating during full auto. Try putting some telfon tape around your barrel to stabilize it in your outter barrel, and make sure everything is tightened down.

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I know I'm a bit late to the party but I figure I'd post my results.

 

Gun: g&p m16 vn

Fps: 398

Barrel: Madbull 6.03 mm

Bucking: systema (blue)

Nub: just a soft eraser glued to the hop up arm

 

All I had for the test were .25g golden balls.

 

I measured my target out to 75 yards (225 ft). Target was a plain sheet of paper.

 

On semi auto I was getting about a 3 inch grouping. On full auto it spread to about 1 foot (not sure why).

 

I must mention that it was pouring down raining. Not bad for about 10 minutes of work.

 

Once I get some .36g in I'll do another test.

 

 

wow, those are some unbelievably nice results, especially with .25 at only 400fps . Do the bbs hit the target with a flat trajectory or with some overhop?

 

Can't wait to see your results with .36 , well done :)

 

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Is there a general consensus on the best tightbore/bucking combo for the flat hop yet? I'm a little disappointed with my stock KWA SR10's consistency.

 

I'm quite envious of proplayer187's results. So I had the madbull in mind, but I wanted to keep my options open.

 

I'm also open to full hop up units as well. Thanks to a recent promotion, I'm not too concerned on the price.

Edited by Shabby

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Its important you stabilize your KWA's barrel because the damn thing floats at both ends which is probably one of the major sources of your issues. From there try flat-hopping with just stock parts. Don't get immediately sucked into buying things, see what a bit of tuning will do and replace things as needed from there.

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Its important you stabilize your KWA's barrel because the damn thing floats at both ends which is probably one of the major sources of your issues. From there try flat-hopping with just stock parts. Don't get immediately sucked into buying things, see what a bit of tuning will do and replace things as needed from there.

 

I've done the teflon mod to the hop up, and all down the barrel (according to the DMR Holy grail, and it's pretty snug) I had an issue with compression from the hop up unit improperly sealing against the gearbox, but after a few layers of electrical tape to make a soft seal around the edges the issues seems to be resolved. (Barely noticeable movement of paper over the feeding tube according to this guide.

 

I'm going to give the flat hop a shot this weekend (after all, if I'm replacing the bucking, why not test it out) but I wanted to post and get a get a discussion going/few opinions before making a purchase.

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Well, in my experiences, there is no perfect barrel, or perfect chamber. Across the board, you can make them all preform the same through various mods. Especially with M4s, all the hop ups out there are relatively the same, the only exception is the madbull chamber, which is nice in it's own way, but it's compatibility issues really limit it's usefulness. And barrels all have generally the same hop up window, some have rounded edges, some are straight cut, but I've found that doesn't matter as much as the bucking and nub that you use.

 

As long as you cut the nub to fit into your barrel's chamber, you shouldn't see a difference between different barrels and chambers.

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Well, in my experiences, there is no perfect barrel, or perfect chamber. Across the board, you can make them all preform the same through various mods. Especially with M4s, all the hop ups out there are relatively the same, the only exception is the madbull chamber, which is nice in it's own way, but it's compatibility issues really limit it's usefulness. And barrels all have generally the same hop up window, some have rounded edges, some are straight cut, but I've found that doesn't matter as much as the bucking and nub that you use.

 

As long as you cut the nub to fit into your barrel's chamber, you shouldn't see a difference between different barrels and chambers.

 

Interesting. Thank you and HS5 for responding. I'll give the flat hop a shot this weekend and post my results when I'm done.

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Is there a general consensus on the best tightbore/bucking combo for the flat hop yet? I'm a little disappointed with my stock KWA SR10's consistency.

 

I'm quite envious of proplayer187's results. So I had the madbull in mind, but I wanted to keep my options open.

 

I'm also open to full hop up units as well. Thanks to a recent promotion, I'm not too concerned on the price.

 

Honestly I never had good results with my madbull barrel until I did this mod. In fact I was using my stock barrel over the Madbull because I was getting better results. When I did the flat hop mod I chose to use the madbull barrel because of the fps boost I'd get since I was going to be using a heavier bb.

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any word on kraps nubs though I saw the last stage if testing is done when would they be released?

 

The original plan was to ship the nubs out around January 17. The solid nub is fine, but the hollow nubs have a durability issue which I won't be able to solve in time. Instead, I'm replacing the hollow nubs with a solid angled nub, and will be making sure that the consistency and accuracy is up to spec over the next two weeks.

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Star_Folder have you tried one of my M-nubs in a flat-hop system yet? I'd be interested to see what you think. If you'd like a few samples shoot me a PM over on AM with your address and I'll get some samples in the mail. The M-nub wasn't designed as a flat-hop nub, but I did some quick testing and it does work. I haven't played with a plain "flat-hop" in years though so whether or not its performing as well as other flat hop nubs I have no idea. Thats what I'd like your opinion regarding. :)

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Thought id add my effort after extensive research, I went for a concave design with extended barrel window. Hop is fully on here to show the shape etc, looks good to me but havent tested it due to needing a new piston in my KA Galil MAR. Sorry for the necro but hey its exempt lol

 

2012-01-05102647.jpg

Edited by Joe90

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There's no necro, the last post was only a few days ago. And that looks remarkably well done. What did you use for the nub, and how did you cut the barrel. I'd really like to see pictures of the barrel's cut if you have them. And is that a G&G green bucking or some other brand?

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Ahh I see sorry I thought this was all old news lol, the barrel was done with a dremel so by eye really, then tidied and cleaned, the rubber is indeed a g&g standard, too thin really but its what I felt like cutting up for test purposes. The nub is the concave peice of a pen lid, the bit youd clip on your shirt, with smoothed edges and I also made the concave a little deeper, that then sits on an extended hop arm which allows a see saw like movement to a small degree as to reduces pinch jams, need to test it but looks promising.

Edited by Joe90

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Ahh I see sorry I thought this was all old news lol, the barrel was done with a dremel so by eye really, then tidied and cleaned, the rubber is indeed a g&g standard, too thin really but its what I felt like cutting up for test purposes. The nub is the concave peice of a pen lid, the bit youd clip on your shirt, with smoothed edges and I also made the concave a little deeper, that then sits on an extended hop arm which allows a see saw like movement to a small degree as to reduces pinch jams, need to test it but looks promising.

 

When you test, I would be very careful of jams, but I think you already know that. There will be very little "give" in this system (a little bit in the arm, bucking, and the nub flexing). You might want to make a backing of some sort of rubber.

Edited by krap101

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I agree with crap, if don't have rubber somewhere in that nub, it will be very easy to cause jams and to rip your bucking, just be careful. Adjust your hop REALLY slowly.

 

On a side not. I attemped making an ER-hop length flat hop, but it failed. The bucking would cave into the barrel, It's possible that it would work with a hard bucking, but I haven't tried yet. Seems like a hop length longer than 8-7mm runs the risk of failing.

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I agree with crap, if don't have rubber somewhere in that nub, it will be very easy to cause jams and to rip your bucking, just be careful. Adjust your hop REALLY slowly.

 

On a side not. I attemped making an ER-hop length flat hop, but it failed. The bucking would cave into the barrel, It's possible that it would work with a hard bucking, but I haven't tried yet. Seems like a hop length longer than 8-7mm runs the risk of failing.

 

Try making some sort of rigid backing (like his pen cap), and use a softer rubber (sorbothane seems like it would work nicely)

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yeah I get what you mean, I used the same system on my vsr and although not an aeg I was careful with adjustments, also the rubber will be getting swapped out for a thicker madbull blue for more padding. I added rubber to the bottom of the pen cap at first to pad it out but lost alot of the shape. so went back to hard. just need to test it now.

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yeah I get what you mean, I used the same system on my vsr and although not an aeg I was careful with adjustments, also the rubber will be getting swapped out for a thicker madbull blue for more padding. I added rubber to the bottom of the pen cap at first to pad it out but lost alot of the shape. so went back to hard. just need to test it now.

 

I just thought I'd caution you, because I tried hopping .40g with my alpha nubs (polycarb upper with sorbo lower), and it ended up jamming because of the hard upper. What you might try is shaping a piece of rubber and attaching it between the cap and the arm, that way you'll have some give, while keeping the concave shape.

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I just thought I'd caution you, because I tried hopping .40g with my alpha nubs (polycarb upper with sorbo lower), and it ended up jamming because of the hard upper. What you might try is shaping a piece of rubber and attaching it between the cap and the arm, that way you'll have some give, while keeping the concave shape.

That sounds like a good idea to aliviate any stress. baring in mind here in the uk im only ahooting 350 fps tops so I wont be trying to hop anything largwr than a .3g I wouldnt imagine. When I get my piston for this galil ill be sure to keep the thread updated.

Edited by Joe90

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Initial tests of the M-nub show that it is not thick enough for a flat hop application. Upon properly modifying the hop up arm, the nub doesn't put enough pressure on the bucking to give any hop at all.

 

It also appears to be not quite as accurate as other nubs I've used. Though it still provides the longer contact patch, the edges collapse on the nub when under pressure, and it results in a more traditional contact style convex shape. But I'm still running some tests with it to see how it fairs under different situations.

 

For that matter, sorbo doesn't make a good nub either, same problem as the m-nub, it's too soft.

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