Permanent compression happened for me for rubbers under 10A, and I've gone as low as 0010, which is something like 10-15x times softer than the 40A that you probably used. I've found that rubbers nearer the softer end to be more consistent, but as you go softer, you'll see issues like permanent compression and inconsistency from slower expansion times (so you'd need to slow down on semi to ~1rps or so)

Oh, wow, that's way softer than what I was using. I was talking about 70D sorbo being too soft, much less 40A or anything softer. Once I started going softer, and found results to be less consistent with harder nubs, I stopped trying them out. That is incredibly soft for a flat hop, as for consistency, again, I found my harder nubs to be more consistent than the softer nubs.

Looks like I'll have to do some testing with both types of nubs then haha.

So then, should I try to cut out that barrel window?

And from the buckings I have on hand, what should I use for the flat hop at 500 FPS, 25 RPS? (KA hard, systema, shs hard, shs soft, madbull blue)

Thanks alot.

How were you mounting the nubs to the arm?

I would go with Mad Bull, I use the red with a 465fps setup and it's excellent. I would avoid silicone like the SHS buckings unless you're going with an R-hop - then they are great.

Posting my results after fine tuning this mod.
Internals
Stock Army Armament 6.02 or 01 Brass Barrel. (its tighter than my .03 Madbulls). I need to get a Micro Calipur to confirm this).
G&G Armament Grey M4 hop-up chamber
Dollar Tree Flat hop-nub
Shooter Aluminum pistion head
Shooter 14 Tooth Steel Rack Piston (with Piston spacer mod)
Guarder M14 Steel Standard Torque Gear set
Stock Compression parts (I.e Cylinder, Cylinder head, Air nozzle (has an oring))
SHS M140 Spring
Element Ultra Hight Torque motor
11.1v 20c 1300 MAH Lipo Battery.

My FPS is around 462 and bounces from 460-464 fps on .2 gram bb's.
My first attempt I chopped up a old ACM bucking as a proof of concept test, and use some Dollar Tree School erasers (all the colors of the rainbow+pink)
After seeing the Inproved range over a SCS+Madbull red bucking I thought cool. the cut job was terrible and I made a hole in the old mount area while cutting.

The second bucking I used was a SHS Hard bucking. Worked well for about 250 shots then Tore up from use of .32 gram bb's (Overhopped .32's at the lowest hop setting).

Third bucking, I chopped up the madbull red. Shot more .32s, Still overhopped them. but able to Guide them to a Target that measures 2 Feet Tall, 5 Inches Wide and able to hit that target 2/4 shots @ 240 feet. Im sure if I had .36's or .4s that consistancy will be increased further. (Spread @ 240 feet was about 1 foot). All in all I fielded this gun @ a skirmish/scenario game last sunday. Was able to get a confirmed 200 foot kill and racked up a few other kills while playing DMR for my squad. Although I WILL ADMIT, I wanted to do the lone wolf thing but. we all know that ends up with walking back to the respawn point in 2-4 kills.


I have a feeling im riding the express train to Tacticool hell XD

This post has been edited by J-man: Mar 6 2012, 04:19 AM

Yeeeeeeeeeah, I really hope you rot in it.

Good results though. What is the maximum you can engage...say a torso, or full man sized target.

This post has been edited by sniperelite7: Mar 6 2012, 04:41 PM

@ sniper. Ill find out in 2-3 weeks when I plink down for .36/.4 gram bb's, But im sure 250+

At this time with overhopped .32's about 230 feet.

What bb weights do you guys typically use with the flat hop? I use .25g KA Platinum bb's with my upgraded CA AUG, that I've done the flat hop mod on. It shoots approx. 350 fps with .25g bb's. I'm thinking of trying with .25g or .30g bb's.

The grouping seems to be pretty tight out to about 130 feet, after that they spread out. I haven't tested it properly yet, but I don't seem to get quite as good range as you guys do. I haven't had any problems with overhopping, and the hop up is easily adujsted, so at least it's not worse than a regular hop up. ^^

I'm still experimenting with the nub, I copied lionhardt64's eraser nub and I guess I'll just continue tweaking that result and see if I can make it work.

This post has been edited by Lefse: Mar 6 2012, 07:26 PM

My nub that im using is nothing but Block. So far its working. It Pivots on the arm and hasnt deformed or broken up yet.

Waiting for light 2mr but gonna set up targets @ 50' 100' 150' and 200 Feet and do a 10 shot test on each

To stop from overhopping just shave down the nub slightly - that will decrease the protrusion of the nub into the barrel window and reduce hop.

Bad day for Testing, 15 mph winds with gusts up to 23 mph. Tried to do a 50 foot test in the wind on a 8x11 peice of paper, Made a 3 inch bull's eye, My shots where all to the left but had a 3 inch grouping in the wind. on .25s As for over hopping, I need more white .25 and a sunny day to confirm the fix, but Rotated the madbull bucking so its dual feed prevention lips are not inline with the hop-up. appers to have partially solved that issue.

Cant verify till we get nicer weather up here.

Just adding that I found the Firefly nubs back in stock at Amped, in case you don't want to make your own.
http://www.ampedairsoft.com/product_p/ff-namazu-flat-nub.htm

http://www.ampedairsoft.com/product_p/ff-namazu-flat-nub.htm

"Pre-Order: We currently are waiting for a restock on these items......"

I believe you may have spoken too soon. :P

After Realinging the Madbull, Washing .3 Grams, Waiting for a nice day with next to no wind. 50 Foot Spread was down to an inch, 100 3-4 inches, I did not do a 150 foot test. as the wind decided to start picking up in the field I was testing. (fixed the overhop issue with a 6.01 barrel, bucking reajustment)

All in all. a 460 fps rifle on .2s (shoot with .3s) Reaching to 240 Feet Acceptable enough with just a flat hop? I got the accuracy down, but I was wondering if the R-hop would boost range further without having to Up the FPS. Our local Limits are 500 FPS for semi auto/Bolt action rifles. the last thing I want to do is hit like 501 fps, and not be able to field the AEG.

Maybe..... maybe not. I'd bring up a couple things.

First you're shooting ammo much lighter than is ideal for your velocity, you might be able to squeeze more range out from just that.
Second 240 feet is short for 460fps, so you might want to consider the possibility that there is something wrong with your flat-hop. Of course range can be a bit subjective. Its worth checking a chrono though to make sure its actually putting out that power.
Third you can get a lot closer to 500 fps than 460 without being in the "in danger of going over range" so since you're probably in the semi-only range already you might as well go for more.
Fourth the R-hop isn't for the lazy, if you don't want to tune your gun for optimal performance both in and outside the GB, I'd say just don't bother. I prefer not to cater to the "shortcut" market, even though the Z-kit is kind of a shortcut as I'm sure someone will bring up. ;)

Hrm. If its that off, ill go back to tinkering with it.

It seems Better then any bucking/nub currentlly out, but Im not 100% satisfied with those results, but I missed the memo. With the Flat hop system is it better to go for a flat nub or Concave?, and Secondly, Semi Hard or soft?

I would love to give the R-hop a try but I want to try .4 gram bb's first then go from there. Any advice is welcomed. Inside the gearbox its optimal. But. Agian Lack of a boneified Chronograph puts that claim as not trustworthy. there is a pick up game on the 25th, gonna bring the l85 along to get it chrono verified. im not gonna try fielding it with the hop-up being off but I feel better knowing that if I did field it, could outrange most of the aeg's ont he field. (Albiert only by 50 feet or so, still is an advantage).

This post has been edited by J-man: Mar 18 2012, 11:31 PM

I've experimented a bit more. I bought some h-type nubs, they were pretty cheap, but seem to be pretty accurately made. They snuggly into the chamber, so should be pretty stable. They're made of fairly hard plastic but seem to work better than the eraser based nub I made first.

It was getting a bit dark so wasn't able to adjust the hop to the most optimal setting, but seems like I've been able to improve it a little. My AUG actually got a bit less power than it had in my first test, as I've short stroked the piston, so now it shoots approx. 350fps with .2g bb's. The barrel is a Systema BS 6.04mmX509mm. Maybe a Mad Bull 6.03mm barrel would be slightly better, or should I just stick with my current barrel? It's a pretty snug fit in the outerbarrel, so it's completely stable inside the outerbarrel, which is an advantage.

Under optimal conditions, with a bit more power I think I would be able to hit an opponent at 200 feet. I only paced out the distance, so not very accurately measured out, but the range I'm getting now is almost twice what it had stock, so I'm quite pleased with my reults so far. I'm getting a nice profile on the bucking with the h-nub, and no problems with overhopping so far. I actually had to make a spacer out of wire insulation to get enough spin.

Here's a photo of the first "eraser-type" nub I tried, and my current h-nub assembly:


This post has been edited by Lefse: Apr 13 2012, 06:40 PM

ima have to try something like this. my gun shoots pretty hard and fast but drops quick after 50ft. dialing the hop up doesnt change much

That would indicate that there is an issue with your gun, most likely around the hop up/barrel area. Simply changing hop ups probably isn't going to fix the issue. You should be able to shoot ~150ft with the stock hop up. This of course depends on things like velocity and bb weight, but regardless, you should get a lot better range than 50ft.

I've never taken the time to fully read this post, so I read it from beginning to end. My opinion? It's LONG! LOL! Seriously, though, I have a lot of thoughts and theories, some that might be useful but most are likely worthless ;-)

First of all, I had no idea that Firefly nubs were so difficult to find. I've seen them on Airsoft Atlanta for quite some time, and just ordered one today (I think they have them all in stock--soft, regular and hard). I ordered the hard nub. I just wanted to pass that along in case anyone wanted to order one.

Secondly, I just have to say that every single one of you guys are just awesome. AWESOME! I've always loved to tinker with things, and have broken more trinkets in my time trying to dissect them than I can remember. Threads like this are right down my alley.

Anyway, I have tried the r-hop, and after making a dartboard out of Hunter Seeker's logo out of frustration, I had great success. <grin> I'm always bad to get into a big hurry, and this is what I did with the initial r-hop install. Surprisingly I had the perfect outer fit almost from the start, but in my attempt to get a concave shape in my barrel I ended up cutting too much. Thus, I just ordered some more material to go back and do it the right way (it didn't work at all for me at first, then I tried placing the r-hop with my bucking rolled back so it hopefully wouldn't shift as opposed to dragging the bucking over it. Worked AMAZINGLY well, but due to taking off too much material it wasn't stable... starting getting inconsistencies in performance). Note: READ the directions for the install. RE-READ the directions for the install. Watch a video or two or ten. RE-READ the directions for the install. Sleep on it. Now you're ready to do it, and you will not be disappointed.

As stated, I ordered the firefly nub today, and plan to make a flat hop this weekend to try it out. It is truly a very simple, but seemingly effective, approach to greater accuracy at greater distances--something I sorely need. I've seen several people complain about the logevity of the bucking on the flat hop, with a lifespan of 20k rounds or so. At $5 to $8 for a soft bucking, I feel that it's a good trade. I just paid $15 per bag of KSC 0.30 bb's (2200 bb's per bag), so that's about $150 I'll spend in bb's to reach that mark. And, according to Star Folder, he has 40,000+ rounds on all of his flat hops and only had one break (at 20,000 rounds) to date. With that said, I know that to a lot of people, either because of finances, by choice or some other reason, don't want to have to spend money on a new bucking every so often, and that's cool. But if you are going to go this route, you're going to have to buy premium bb's--even if you use 0.2's--to make it worth the effort. That's going to cost extra. Same with the r-hop. If spending extra money isn't something you want to do, just don't do it. MOST of the guys I play with are perfectly content using $80 to $100 AEG's with 8.4 NiMH batteries, 0.2 generic bb's and never even adjust their hop-ups. Does it really matter if they're having a ball? The sad truth is they probably kill me at a 4:1 ratio ;-) And I do understand how it would be frustrating to a lot of guys to have to bother changing the bucking more regularly. It can be a hassle. But seriously... would anyone in *this* forum--a forum of tweakers--really mind having a good excuse for tearing their gun down again? Just the other day I removed my barrel and hop-up and put it back together again... for absolutely no reason.

Anyway, it's all good. I truly doubt if any manufacturer is going to standardize the flat hop and/or the r-hop... ever. They both have their challenges--not problems--but challenges. The level of quality control that would be required would be significant, and there just aren't many people in airsoft who can or would want to spend the money it would take to make an accurate 100-yard range gun. In truth, do you really want that to happen? There's only so much you can do with the physics on a 6mm plastic bb that weighs less than 1 gram, and what fun would it be to know that almost any tweaking you do will make things worse? If that were the case, all of my interest in airsoft would be gone.

A couple of notes... I noticed one guy suggesting electrical tape as a bucking, and I think it was Star who explained that you need the bucking taper at the head of the barrel for an air seal. You could use a partial bucking for that, and wrap the electrical tape to seal the partial bucking, but electrical tape has too little elasticity--it's yield point is very low and becomes plastic with very little stretching (permanently deforms).

I also saw a bit of an argument on barrel pressures. It really wouldn't be that difficult to create a digital profile of pressure vs time inside of the barrel of one of these guns, and that's something I might just do if everyone feels it would be of benefit. However, I just don't see the point. Due to different cylinder designs, nozzle and bucking designs, potential for air leaks, different barrel bore sizes, etc., they would be all over the place. For instance, take my cylinder and my barrel. The G&G F2000 comes with a 6.04mm bore, 430mm barrel. If you calculate the internal volume of the cylinder, its air volume is twice that of the barrel once compression begins after the port. So--even with a moderate velocity of the piston (which would mostly negate leaks), the bb has left the barrel when the piston has traveled only 1/2 of its compression stroke. Thus, the volume of air is somewhat insiginificant once you pass the 1:1 ratio. It is simply the speed at which the air is compressed that makes the difference, which is the result of the strength of the spring. You could actually calculate the pressure generated by this compression, but it's not the simple PV=nRT. It's not a closed system. As soon as the piston begins to compress the bb is moving. In soft buckings I can usually blow the bb through the bucking, and humans can usually only blow 2 psi at 1 atm of pressure. (BTW--if you get a chance, do this, and aim it at your leg--it HURTS!). Thus, the receiving chamber is already expanding. Thus, the "V" part of this equation has already become dynamic. The variability of "V" becomes a function of the velocity of this expansion, and, you get the point. Although air is a very imperfect fluid (one biggie--it compresses), it still has fluid behaviors. How does the cylinder translate into the nozzle? Does it have sharp edges, or smooth, rounded edges to assist in reducing turbulent flow? Nozzle to bucking? Etc. In my opinion, the highest pressures--by far--will occur in the cylinder near the face of the piston. Every particle on earth has a resistance to movement--in our case, drag--and this will occur closest to the object creating that movement.

Take a look at the cylinders in airsoft guns--they are quite thin. If you'll go to Lowes or Home Depot you'll see that the larger the pipe diameter the thicker the material will be. If you'll really look closely, you'll find that despite the thicker material, larger pipes have a lower PSI rating in the schedule 40 class. There is just so much more surface area for these "pounds per square inch" to act upon. As a rule, brass is not the ideal metal to use for thin-walled pressure applications, which most cylinders seem to be made from. Cylinder diameters (normal) are 22mm--almost one inch. Schedule 40 c230 brass pipe has a pressure rating of appx 600 psi. It has a wall thickness of 0.133 inches--over 1/8th of an inch. Airsoft cylinders are likely around 1/32nd of an inch, so their pressure capabilites before deforming/failing are much, much lower. I would be completely shocked if the maximum pressure inside of the cylinders reached anywhere near 40 or 50 psi... that is a lot of pressure to be applied again and again and again for such a thin-walled cylinder.

Without question, barrel thickness is only there to keep the barrel from bending easily. At equivalent pressure a 6mm ID tube will have 1/13.5 the amount of surface area at the same length as a 22mm tube. Thus, it can be much, much thinner. However, for ever 1 unit of length the cylinder compresses, 13.5 units of air are going into the barrel. But... the volume for that air is expanding at an accelerated rate, up to the fps of your gun. Thus, the pressure could actually DECREASE as the bb moves in the barrel (say the initial pressure inside of the barrel is 60 psi, but is reduced to 20 psi by the time the bb leaves the barrel), but as long at the pressure remains positive (not a vacuum) it is still accelerating the BB.

Chances are, given the dynamics of airflow and the restrictions of moving this air into a smaller orifice, that the bb isn't moving perhaps 30-40 fps when it passes the bucking. Think about it... would it not be more consistent to apply the backspin when the BB LEAVES the barrel??? Imagine the bb having to travel through a barrel that is 430 mm long like on my F2000. So much can happen in that time... a bump on a wall, a piece of tiny debris--anything. It could totally mess up the trajectory. So why don't they put the bucking at the end of the barrel? Or at least in the middle? I imagine it's because a hard, plastic bb hitting a soft bucking at 400+ fps would destroy that bucking incredibly fast. Also, it would slow the bb down quite a bit, whereas with the bucking at the beginning of the barrel allows the bb to accelerate the whole length of the barrel. AND... the contact time on the bucking would be 10x less....!!!

I guess to sum this up, the air pressure created by the piston has no effect whatsoever on the bucking. Air has extremely low viscosity until you reach speeds well above anything an AEG can put out (but can certainly melt steel at hypersonic speeds). By far the largest wear will occur from the bb hitting the bucking, and my guess is that the bb is passing the bucking not at the fps rate of your gun, but at a much more liesurely pace of 30-40 fps. Jams, of course, where the bb gets stuck and allows pressure to build behind it, can impart a significant pressure on the bucking by pressing against the nub and could cause immediate failure (even if the pressure is "only" 50 psi... spread this across the bb, and then translate this to a point-load against the edge of the nub through the bucking... it could theoretically be hundreds of pounds of pressure against that one edge--solids impart force/weight directly (unless they deform--like pulverizing a bb)--unlike liquids and gases that conform to equalize pressure).

One last note... regarding pressure in airsoft guns, I feel it won't be anywhere near 600 psi. As stated above, the cylinder won't handle it even in instantaneous bursts--especially thousands of times. If the volume reduction from the cylinder to the barrel increased pressure in the barrel the piston would cease to compress--you can't push 50 psi air into a region of 51 psi air. Physics loves equilibrium. Thus, the controlling "pressure" is the cylinder. My theory on muzzle velocity would lean more towards the pressure capability of the spring and how quickly the cylinder can supply and maintain an air pressure within the cylinder to the barrel. Say an m170 spring is capable of compressing air to 45 psi. This can EASILY be tested with a closed cylinder and a piston pressing into the chamber. Static pressure. Now--let's open up a valve allowing this pressure to be relieved. The air travels into a barrel pushing a bb. As this occurs, the receiving chamber expands (since the bb moves) which would attempt to reduce the psi (since the air pressure on the other side of the bb is less). However, the spring will then travel trying to reach equilibrium (to maintain 45psi). Which travels faster? The spring or the bb? Remember--the spring only has to travel at 1/13.5 the speed of the bb. If the average velocity of the bb is 200 ft/sec (from sitting still in the bucking until leaving the barrel at 400 fps), then it would leave a barrel like mine in 0.007 seconds. So--which is faster? It really doesn't matter. As stated above, my cylinder volume is twice the barrel volume, so as long as the spring compresses fully it is imparting a positive pressure on the bb. Even a pressure of 1 psi will still accelerate the bb. The only problem I would see is if you short-stroked your piston reducing the compressing volume and had a very long barrel. But even then, it would require--for a stroke of 1.5 inches coupled with a 6.04 barrel--length of 20 inches (508mm) assuming no losses to actually go into a vacuum on the bb. BUT... it depends on the bb velocity and the ROF. Assume you have a bb velocity of 300 fps, with an average velocity of 150 fps. It would leave the barrel in 0.011 seconds. As long as your ROF was no more than 91 rps, no vacuum would occur because the bb has left the barrel. Side note: this is why I feel "barrel suck" is mostly a wive's tale... unless you have a crazy ROF, a very long barrel, very small effective cylinder length and/or horrible air leakage. And I'll guess that anyone who has gone to the trouble of making a 500mm rifle with a 90 rps rof will have ensured they have no air leaks :-)

Wow--sort-of went off on a tangent there, didn't I?

Would love to add more, but it is way past my bedtime. I'll be sure to post back my results, and I'll do my best to keep track of my rounds fired on the flat hop to see how long it lasts.

I know this is kinda an old thread, but I was experimenting today and came up with a simple mod to the flat hop that I don't think anyone has tried yet. After the mounds on the bucking are sanded down, most people rotate the bucking 90 degrees on the barrel and leave it at that. However this leaves a large space where the barrel window is, which requires an extra large nub to apply normal hop. So I took an old bucking that wasn't being used and I cut out a patch that was the exact size of the barrel window, and set it in place and then slid the bucking over it. Basically it was the same concept as the r-hop except it was flat.

Results were pretty good, I was able to get the same accuracy at 210ft that I used to get at 180ft, and that was with .28g. For a gun that shoots around 400 fps I know its short, but I wasn't using a flat nub and the extra piece of rubber that I added wasn't glued to the bucking. Let me know if you guys think this is a worthwhile mod.

Correct me if I'm wrong, but I believe what you are describing is almost exactly G-hop.

Essentially what greg70 did was the G-hop. When I did my research though, the part of the bucking was actually glued to the barrel window, rather than the bucking itself. So really it is sort of a trifecta of G-hop, R-hop, and Flat Hop.

Just looked up the g-hop and it seems thats what I basically did. But is the flat hop better than the g-hop? If so, why?

The flat hop is better. While the G-hop was a great start to the race to extend range, it suffered from one fatal flaw. It was extremely easy to suck the little patch that fits in the window, into the barrel and cause a jam. With the R-hop, we got around this issue because the rubber is more firm, and is concave rather than flat, which helps almost alleviate the issue. Radiusing the trailing edge eliminates it.

The Flat hop doesn't suffer from this, however due to its design, it can be challenging to lift heavier bbs without ripping the bucking.

Here's the latest thing I'm trying, hoping to get a bit better groupings. The bottom is made of two layers of rubber cut from a bicycle wheel tube. The upper part that goes into the hop-up arm I made by grinding off half the diameter of a 4.2mm diameter screw, and then cutting it to the appropriate length. This should make the nub alot more stable, hopefully improving accuracy. I also cut a "trench" under the nub, to increase the contact area. I haven't tested it yet, will try and test it tomorrow to see the results.

With my first nub based on bicycle rubber I made the upper half out of a half regular nub with a piece of wire stuck into the hole to stabilize it. I didn't cut a trench in that nub, it was basically just a short firefly nub. With that nub and 380fps <AT>20g, I was able to squeeze out about 230 feet. My groupings are quite wide though, but I think that's mostly caused by vibrations in the barrel, as it's an AUG.

My new steel and rubber nub:

The nub must be like the picture below?
Red piece must fit to the barrel window?

http://i46.tinypic.com/1zwgqs4.jpg

Black=barrel
Blue & Red=Nub
Grey=Hop-Up

Yes. You want the red piece to be slightly smaller than the window so that it does not get jammed against the bucking that it is pressing in. Remember you still need the bucking installed over the barrel.

Instead of reading through 12 pages I just thought I'd post. How does the Mnub work with flat hop?

Pushes down on the hop rubber

I know that, I was wondering how it compared to other nubs for flat hop use.

It works great for me. I use it in a A&K CQB M4 with 0.30g bbs, and maintain tight groupings past 200 ft

Alright, Ill go test it out later today.

I think earlier in the thread I said something about not liking m-nubs, not sure if I ever revisited that subject, but depending on your set up, they can actually be too thin and no apply enough hop. I've used them a few times now, but depending on the hop up arm, I've had to add in material so that they press down far enough to properly hop bbs.

Some hop arms really don't have much travel and using a flat hop really adds to the distance you might need to push because all your used rubber sits outside your barrel. The two critical things are that your M-nub does not sit too far outside your hop window (otherwise it'll resist being pressed down in for obvious reasons) and that if you don't have enough travel and such its easy to attach something rigid and thick to it because its adhesive backed. You can always do something like take your stock round nub, cut it in half longitudinally, and stick that half on top of the M-nubs sticky backing to add that extra little oomf. On something like an M4 arm that'll not only give you some extra depth, but also allow the M-nub to press out of the way at the sides a little bit allowing it to squeeze the bucking into the window.

All that said I will confess I don't spend all THAT much time toying with the M-nub and flat hop. When you have so much R-hop installing and testing to do, there aren't many "empty" barrels sitting around just begging for something to fill them. ;)

I just tested with good results! BBs fly flat to 220ft and then drop. 330fps with .20g bbs. With .25s should I expect 250 ft or so?

Try it and find out. I'm impressed you're getting 220ft flat with .2s.

How are your groupings with the 0.20g though?

I read the first 8 pages and couldnt go on anymore.
Can someone explain what a M nub is?

And, what household material is best for filling the gap between the nub and bucking? Bike tire tubes? Erasers?

This post has been edited by anzezaf: Sep 24 2012, 04:35 PM