|  Author | Topic: VACS - A DIY hop mod for everyone!? (Read 98 times) |
vindicareassassin
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Karma: 14 |  | VACS - A DIY hop mod for everyone!?
« Thread Started on Oct 31, 2009, 6:23am » | |
Well as I promised Woogie and as suggested by Zulu in my DIY Firefly hop thread an alliterative to buying the SCS nub, I'll call it the VACS 
The reason for doing it.... I don't like H nubs as they are square in profile so the distance between the actual contact points is diminished, I liked the idea of the SCS, but refuse to pay for anything I cant make myself and they are dam near impossible to acquire over here anyway, plus they are both just floating about in the hop chamber with only the rubber and arm to hold them in place, alright if the nub fits snuggly in the aperture, but check out the width difference between a VSR hop arm and an M4 and you'll get the picture  and as alot of people are using the SCS in the VSR and finding out its shooting in all directions because theres to much chance of it moving to make it reliably consistent and all this after they've sent their one and only arm down the road to SCSvile with no return ticket.
First the disclaimer..... You should only attempt this if you have some degree of mechanical or modeling skill, I can not be held responsible in any way for your technical incompetence, so if you feel that after reading this thread you would like to try this and f**k it up, its your fault not mine 
What you will need -
A Dremel with variable speed, plus a cutting disk and 1/4" sanding drum.
Cyanoacrylicate (super) glue, I use a product called Mitre bond which comes with an activator and literally sets in seconds.
Precision needle files
Left to right a rat tail or round, a half round or 'D' and a pointed flat
![[image]](http://i123.photobucket.com/albums/o306/vindicareassassin/Airsoft%20Weapons/B009.jpg)
Some round solid plastic stock of roughly the same diameter as a rubber nub, I use the sprue tree off plastic model kits like this
![[image]](http://i123.photobucket.com/albums/o306/vindicareassassin/Airsoft%20Weapons/B004.jpg)
Some metal shim plate, the thinner the better. Most good model or hardware stores will have this in stock. I use the thinnest gage brass sheet you can get as its harder wearing than the tin stuff you can get.
To start, dis assemble your barrel and hop unit into its component parts.
Next take your barrel and you will need to increase the size of the nub window, as the new nub will not go through the stock opening on some barrels, after opening the window you then need to make sure all the edges are rounded and smoothed of so it doesn't tear the rubber and then clean it/polish it thoroughly.
Stock barrel left, one I modified on right.
![[image]](http://i123.photobucket.com/albums/o306/vindicareassassin/Airsoft%20Weapons/B003.jpg)
Once that is done its time to move on to the hop arm mod.
Take the arm, and using super glue attach a small section of plastic sprue in the groove that you would normally fit your little bit of rubber/H/V/SCS nub
Like so, this is an example from my G&G M14
![[image]](http://i123.photobucket.com/albums/o306/vindicareassassin/Airsoft%20Weapons/B001.jpg)
And an M16
![[image]](http://i123.photobucket.com/albums/o306/vindicareassassin/Airsoft%20Weapons/B007.jpg)
It is VERY important that you get it on perfectly flat and level or you will find when you put it all back together the BBs will pull to 1 side or another, and thats bad
When the glue has dried you then need to file a groove in the section that the BB presses against, take your time and test it with a BB every now and then, you need to make sure its even from side to side and not to deep, also don't go right to the edges, as you'll see in my pictures the outside edges are slightly radiused, and this is important so you don't cause the rubber to rip as it pushes the rubber into the hop window. You will also need to file in a lead and exit groove that flows into the main groove so the BB passes under in a nice flow rather than off two sharpe edges.
Again I reiterate take your time with this as its the be all and end all of the mod, get this wrong and it'll NEVER be right
For those that say it can't be done to that degree of accuracy, it is widely accepted that the MK1 eye ball can distinguish differences to around 1Thou, all you then need to do is correspond your filing talents to the same degree
If it helps, I used a engineers caliper (non digital) to ensure the high points where exactly the same on both sides from the back of the arm.
![[image]](http://i123.photobucket.com/albums/o306/vindicareassassin/Airsoft%20Weapons/B008.jpg)
![[image]](http://i123.photobucket.com/albums/o306/vindicareassassin/Airsoft%20Weapons/B002.jpg)
Now take your hop rubber and fold it inside out, this going to be the most controversial thing to most of you and I fully expect you to pull this face  ......, you need to sand off the entire nub from the inside using the dremmel and sanding drum, following the technique I described in DIY Firefly.
Like so....
![[image]](http://i123.photobucket.com/albums/o306/vindicareassassin/Airsoft%20Weapons/B006.jpg)
You have to make sure that every last part of the nub is removed, using sand paper/ wet and dry, as this WILL directly affect the accuracy of the weapon as this is all the BB will be using to gain grip now
The reason for removing it is, its just a lump of rubber/silicon that will flex and make everything less stable, and the best cure is to remove it
If you've managed to get this far and not thrown your files out the pram it now time to start to re assemble the hop unit.
First, put the rubber back on the barrel, if your doing this in an AEG I just do the usual sealing with Teflon tape, but when I did my VSR I 'Whipped' the rubber to the barrel and at the nozzle end. The reason for doing it.... It doesn't stretch like Teflon so you can fit it on using more tension thereby squeezing the rubber on to the barrel, thus producing, if you did it right, a guaranteed 100% air seal 
Ill describe what I did then show some photos so you get a better idea.
I used High strength Nylon impregnated cotton thread. Holding 1 end i then carefully wound the cotton round the barrel/rubber joint for 4 to 5 turns, making sure you don't go over the barrel window, then using a dab of super glue, seal the ends and a couple of spots around the thread to hold it in place, make sure theres no blobs by wiping around it to smooth them off, let it set then trim back the tails, job done. To do the nozzle end you need to make a spacer so it doesn't compress it to the point that you cant get your nozzle in when its reassembled ( on the VSR rubber I cut a notch out of the location lug to enable me to wind around it un hindered, but still leaving enough lug to locate properly ). Its abit more labour intensive and messy than Teflon tape but the results are worth it
Nozzle end whipping....
![[image]](http://i123.photobucket.com/albums/o306/vindicareassassin/Airsoft%20Weapons/B005.jpg)
Barrel end whipping....
![[image]](http://i123.photobucket.com/albums/o306/vindicareassassin/Airsoft%20Weapons/A098.jpg)
Now thats done, assemble the hop so that the arm is free floating in the chamber, and check its side to side play at the nub end. You now need to illuminate as much of that as possible, using shims made from your shim sheet material, and maintain the hop nub smack in the middle of the hop window. The method I used was to make side shims that followed the shape of the side of my hop chamber for both sides. I then glued these to both sides of the hop chamber, making sure they were flat and even with no wrinkles. I then used 500 grade wet and dry to sand down each side of the hop arm EQUALLY until the arm was a push fit in the slot. The ideal is to have the arm held firmly but still be easy enough for the adjuster to move it without force. Again take your time and do it right, it all directly affects the end result
Now its time to completely rebuild the gun and test it/set it up.
You will find that because the nub is solid and there is no rubber nub inside the rubber the adjustments you make will need to be VERY small to give quite a large effect. Some of you will find, depending on what size plastic rod you used, that you will get over hopping, the G&G arm above was over hopping a .36 BB with the hop fully off , if this is the case, you will need to take the arm back out and file away the top of the nub by about 1mm (1/32"), then re file the profile again.
The rifles I've currently done this mod to and am very happy with the results are my A&K SR25, G&G M14/21 and my VSR, all are laser beam straight and things to be feared 
Good luck and happy modding
VA
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General Airsoft Weapon Tech and VSR Guru, so I suppose that makes me a BAR 10 Guru too ;-D
Weapons List(as its the trend ;-))
Very heavily modified VSR G-Spec/M40A1/M24 Hybrid
Heavily modified G&G Mk14 Sage EBR MOD0 (Semi only)
Heavily modified A&K SR 25 (Semi only, sub 350 fps)
Soon to be released special SASS project, till then its confidential
HFC Berreta M9
And a Shot gun |
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zulu
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Karma: 6 | | Re: VACS - A DIY hop mod for everyone!?
« Reply #1 on Oct 31, 2009, 2:03pm » | |
All I'm going to say is you could make a fortune doing mods for people who don't have the time or expertise to do some of this stuff themselves
This is my next project for my bar-10, but I don't want to attempt it when I've got a game tomorrow and no backup rifle at the moment.
By the way, this is definitely sticky-worthy. Hint, hint 
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Maruzen L96: FF teflon cylinder, power accuracy cup, PDI 220 spring, steel spring guide, 3 element piston, taper cylinder head pro, PDI hop up+guarder bucking, promo 509/6.03 mm barrel, PDI barrel/AI type 1 flash hider, Laylax zero trigger, SCS nub, PDI "high" arms
Bar-10 g-spec, stock/modded.
KSC USP .45, system 7.
UTG M3 shotgun, full stock. |
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vindicareassassin
Mother Nature
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Just led here relaxing!
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Karma: 14 | | Re: VACS - A DIY hop mod for everyone!?
« Reply #2 on Nov 1, 2009, 4:33am » | |
Ta!  but my barrel polishing thread still hasn't been yet, so not expecting anything to happen soon
|
General Airsoft Weapon Tech and VSR Guru, so I suppose that makes me a BAR 10 Guru too ;-D
Weapons List(as its the trend ;-))
Very heavily modified VSR G-Spec/M40A1/M24 Hybrid
Heavily modified G&G Mk14 Sage EBR MOD0 (Semi only)
Heavily modified A&K SR 25 (Semi only, sub 350 fps)
Soon to be released special SASS project, till then its confidential
HFC Berreta M9
And a Shot gun |
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woogie
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Karma: 6 | | Re: VACS - A DIY hop mod for everyone!?
« Reply #3 on Nov 4, 2009, 9:25pm » | |
Very nice write up bud!
I saw the hop up arm for the M16 in the last thread and thought that was your mod But still a very great idea. Been looking for an SCS as well, and haven't been able to find one, especially since they are around $7.00 here in the states.
I may just have to give this a try on my UTG L96  Could make for a really fun winter project.
And the filing should be easy as I currently have MK2 eyes and am testing some MK3, with MK4 on the drawing board
+1 from me dude :D cheers
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you may want to look at that bush twice before walking by..
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silentfury214
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Karma: 0 | | Re: VACS - A DIY hop mod for everyone!?
« Reply #4 on Nov 5, 2009, 7:38pm » | |
Nov 4, 2009, 9:25pm, woogie wrote:Very nice write up bud!
I saw the hop up arm for the M16 in the last thread and thought that was your mod But still a very great idea. Been looking for an SCS as well, and haven't been able to find one, especially since they are around $7.00 here in the states.
I may just have to give this a try on my UTG L96 Could make for a really fun winter project.
And the filing should be easy as I currently have MK2 eyes and am testing some MK3, with MK4 on the drawing board
+1 from me dude :D cheers |
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they sell them on evike and airsoftgi now.
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Slightly modified BAR-10
WE 1911A1
Echo 1 M16 (broken)
(Coming soon)
G36 Base Project Rifle (broken)
AK 47 Base Project Rifle (broken)
KWA KM4 RIS (new model) |
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woogie
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Karma: 6 | | Re: VACS - A DIY hop mod for everyone!?
« Reply #5 on Nov 5, 2009, 10:13pm » | |
It is more fun to make your own stuff though Been trying to get some ideas on how to make one on my lathe.. But this is a great idea ...
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you may want to look at that bush twice before walking by..
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