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Discussion Starter · #1 ·
Days ago I noticed the stock hop up rubber on my M40 looked as if it was near to get puctured at the sides of the circle-shaped "button" that goes into the inner barrel hop up hole.

This was probably the result of my newbie, not too careful approach to the hop up unit and internals, because the metal barrel cuts through the hop up rubber like butter :)

Feel free to criticize my upgrade, I have -a lot- to learn, I know.

This is a simple at home upgrade.

Required tools:
- Adhesive aluminum foil (the one used to seal chimney tubes or other tubes reaching high temperatures)
- a pair of scissors

How to:
1. Take the hop up rubber out of its seating
2. Cut a small patch of adhesive aluminum foil and stick the top of the hop up rubber to it
4. Carefully, use your scissors to cut the redundant aluminum foil in order to get the square patch the same size of the square hop up rubber
5. Place the hop up rubber back
6. Carefully insert the black hop up unit: this is pretty much air tight and you will need to move carefully to avoid damaging the rubber

This solution works better than teflon/tape because there is simply not enough room around the hop up area of the inner barrel or the hop up unit to roll a layer of teflon and then assemble the unit back.

This added layer of aluminum is very resistant and hold in place by the entire hop up unit (and by its adhesive surface). It makes it safer to avoid air escaping from any kind of slight puncture in the rubber (which could happen from wear/use/disassembly etc.)

The gluey particles you see on the rubber are from sylicon. I tried to seal it that way but I found it to be clumsly and dirty eheh..


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You can gently push the aluminum to the rubber BEFORE placing it on the inner barrel in order to create the circular shape for the part that will get pushed by the hop up regulator pin
 

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This sounds like a really interesting concept, I know my bucking was damaged by the hop nub when I got my M40, but what interests me the most is how different your hop up is to mine. I'm just wondering if mine wasn't the stock hop bucking.

Still, good idea. Does it work in practice? I might do this to my current bucking, because the nub on the spartan doctrine chamber is metal.
 

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Discussion Starter · #3 ·
It worked for me, although now my hop up rubber is completely worn out and will not impress much hop any longer (waiting for my upgrades to arrive, so I don't mind much).

The aluminum foil is very thin yet very resilient and might help when metal nubs are at risk of perforating the rubber.

My hop unit is quite weird, yes..I don't have a rubber bucking, it took me hours to understand what a bucking is actually..there is a metal ring that goes ON the inner barrel and works as a shim, somehow in the way a rubber bucking does.

Having no rubber bucking..I imagine I might have air seal problems but..that's what it looked like in stock form.

I am waiting for my KA chamber conversion to arrive (and aluminum part 91) so it will look different in a couple days.
 

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Yep, that's what I think of too.
Well that's a really interesting design but I don't think I'd like it in my rifle. Got a nice KA airseal bucking in it right now, but I'm looking for a firefly hard bucking in the future.

Thanks for the mod idea, I think I'll use that in my M40 :)
 

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Discussion Starter · #7 ·
You're welcome. I do not like it much, either: too much metal and not enough rubber for my tastes..resulting in possible air seal problems.

Anyway, I am now mangled by an atrocious doubt: when ordering the KA chamber conversion, I did not order any hop up bucking .. I've read everywhere and no store or forum states that a separate rubber is required. I imagine I could buy an improved one, like a KA, FireFly, Nineball etc. (hard/soft types etc.) but so far there should be all I need in that package.

I sure hope so..no bucking, no shooting.. :-/
 

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Well I know that the Spartan Doctrine chamber kit doesn't come with a bucking, so i bought a few KA airseal buckings to go with, and so far I've had some decent results even before they're really bedded in so I hope to see some even better groupings in the future, though I will buy a firefly or maybe a Nineball to compare.
 

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Discussion Starter · #9 ·
I am moving to engage..ahem I mean to purchase a bucking because I fear my upgrades will arrive and I won't be able to install them for a missing bucking :)

At least I got the G&G Rubber set, which is going to be 66% not used when the KA conversion is installed..so I'll still be able to upgrade the gun to a certain point and get my hop back.

70m with Green Gas and 0.40g BBs, *no hop* and consistently on target (man-size) makes me feel really good about the future upgrades ;)
 

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Discussion Starter · #11 ·
That's what I thought. It wasn't a straight shot of course, but it took me around 5 mils up to get there and it got there. Approximately zero wind, target slightly uphill (very slightly).

..but then again: zero hop up, you can't go worse than that lol.

With the PCS and nozzle fully open I am kicking the BB VERY hard out of the barrel, that has to be the reason.

It goes without saying that kudos to the stock barrel. If it wasn't for the bad hop up unit, a teflon-zero-wobble stock inner barrel on this Tanaka M40A1 is a consistency monster (translates into: dreaming of co2).

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UPDATE: Very hit big of luck (we say it in a dirtier way in Italy, but anyway..), I think I got the ONLY Nineball purple vsr10 rubber available in Italy. It is from a store I had never heard about before..ordered immediately.

Reezo's rare find of a Nineball purple VSR-10 bucking in Italy

I am not saying that Nineball purple VSR bucking is the best, all I am saying is that:

1) it is very hard to find any high quality branded hop bucking in general in Italy
2) King Arms are almost impossible to find so you can guess Firefly and Nine ball are among the hardest of finds
3) Even if you manage to find it in the store catalog, 99.9% of the time it is "out of stock" permanently

I will need to guard this bucking with my own body lol I better learn how to maintain the bucking at its best. I don't wanna tear this one!
 

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Discussion Starter · #13 ·
Cerbo Knight said:
Very nice find

Let us know how it performs, I'm interested now
Will do. Since this will probably ship after the Redwolf order, I will test the G&G Rubber set (thus getting the hop back to functional state) and then I will switch barrel and rubber and then test the Nine ball.

For a better test, I think I am going to install the G&G Hop up rubber ONLY, then fire the gun and get a feel for it.



The other two rubber parts are the inner barrel BB holder and then bolt valve ring..I think I might store them away and save them some time since the installed rubbers are kinda okay (the rifle has been probably under 700-800 shots, no more than 1000).
 

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Yep, you may as well use the rubber that you've got until it's worn.

Next thing after a Nineball rubber for me, is to take my fluted barrel to a machinist and get them to find a way to thread it. The G&G heavy barrel doesn't have threads or an endcap :(
 

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Discussion Starter · #19 ·
That is why I ordered the G&G rubber set: bringing my hop back will allow me to test both the improved stock combination..and then the VSR conversion (Prometheus 6.03 555mm with Nine ball purple bucking).

After some time spent getting "the vibe" of the rifle I'll decide what's better. If I am not convinced by the VSR conversion I'll sell it (here :))
 
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