Hunterseeker's R-hop

So my days of being a lurker over at ASM have resulted in me trying out Hs5's new R-hop. It is a difficult hop to install as you are sent pretty much a section of tubing and have to file and grind it to fit your barrel, each hop window in a barrel is different so you it is impossible for him to make a universal hop rubber.  The design is a modification of the Quasar Mod and its derivatives the G-Hop and Flat Hop.

The idea is simple, Make a rubber in a semicurcular shape that fills the hop up window and barely sticks into the barrel. This curved elongated hop will give light long pressure to the bb and provide a much more stabilized consistent hop.  It also for some reason that hasnt been totally figured out physics wise gives a marked increase in effective range.

I installed one in my KWA sr10 and this past weekend took shots I knew to be totally out of my range...AND GOT KILLS!!!
My KWA is shooting under 400fps and is getting at least the same range as Ben's 416 which I know shoots a bit hot. (need chrono to verify)
It definitely shoots at LEAST 20-30feet farther than it did before.

The following pic from Hs5 shows an installed rubber

This next Hs5 pic show what a rubber looks like before it is cut to fit the hop window

This next one shows an installed hop rubber

This particular one is installed in a barrel with very small window, Personally I opened my hop up window a bit to make more of a contact patch.
My Barrel before final grinding/adjustments


And here is what I posted in Hs5 thread...

The trick here is to go really slow for your first install. My first install took several days haha.  Will try and post pics later. (I am at work now)  
What you will need...

Long diamond tipped dremel bit
Fine grit sandpaper...I used 400
bamboo skewers, thick and thin
Tape and glue
Bucking with mound removed


In my first build I didn't realize how much I had to remove from the channel of the rubber to get it to work right.  The first thing I did was to use the dremel to sand down the front and back of the hop rubber until it was the size that would fit front to back in the window.

Then using the dremel I sanded down the flat parts of the rubber so that the top arc of the rubber would still protrude from the top of the barrel over its entire arc.  The flat edges bottom edges were still parallel with each other.  When I would put the bucking over this the rubber would be pushed in and flatten like sniperelite talked about.  So I thought about it and decided to use the dremel to just file down the flat edges of the hop up window until the top arc of the hop was just barely sticking out over the top arc of the barrel (less than 1mm).  Using the dremel to do this was easy.  To make sure the edges of the hop window were still parallel I held the barrel with the bottom slot for the bucking at six o'clock and put a flat toothpick across the window to see that it was perpendicular to the bottom slot.  I then thoroughly cleaned the barrel and deburred it with a small flat metal edge.

(Note that I don't think this is necessary but it will give a larger contact patch. If you want to use the existing window then look at Hs5's picture of the R-hop in the barrel, the inner part that sticks in is smaller than than the outside of the rubber.  This would be accomplished by not having the flat bottom edges of the r-hop rubber parallel to each other but on an angle.  I wanted the bb to contact as much rubber as possible not just at the very top so that is why I extended the sides of my hop window downwards)

So now the R-hop would sit in the window with the top arc of the rubber just barely protruding over the top arc of the barrel.  On the inside the arc protruded over 1mm into the barrel but it had a nice semicircular curve.

I took the sandpaper and worked it back and forth to remove any kinks in the paper.  Then I taped it and glued it around two different sized bamboo skewers. I wasn't sure which skewer would best sand the shape of the bb into the R-Hop rubber. turns out I used a combo of the two.  I took more time than I needed because I would stop and assemble the hop up and test push a bb through every time I did a minute sanding adjustment.  Next time will be faster as i will just sand down the channel to the point where I know it will be close.  

The thing to think about in your mind is that there needs to be barely any rubber inside the barrel to get the desired effect.  Several things will influence the shape of the rubber when it is assembled into the hop up.

1. The bucking will put pressure from all sides so if your channel in the R-hop rubber is not wide enough it will be even worse in the barrel.
2. It your hop window is too shallow it will be hard to get a hemispheric shape to the R-hop rubber, you will more likely see a flat mound in the barrel.
3. If the channel in the R-Hop rubber is too wide it will not contact the bb the way you want and will lose the sideways stabilization.

When you get close the bbs will push pretty easily through the assembled Hop-up.  When you shoot it they will go really straight and then hop up in unison at about 50 feet.  If they are turning to one side or the other you know that your channel is not uniform and you will have to correct that with sanding.  Keep up the process until they level out and hop perfectly with your lowest weight bbs. Then your default set up is done.

The next step is to remove the u shaped part of your hop arm that holds the bucking and glue on something that is flat and wide enough to fill most of the hop window. I am at this step now and plan on using a cut piece of sorbo.

still havent glued mine in yet, wanted to test it first. I did cut a square piece of sorbo to fit the hop up window opening. This weekend it worked great so I will glue it in. Now I will one by one add this hop rubber to my other barrels. I also need to mention that you would cut the mound out of your hop bucking with a razor blade so it has no mound, install your R-hop and then put a dab of Crazy glue on your R-hop, then roll the bucking over our barrel for complete final installation.  To test the rubber while installing just do everything but add crazy glue.  I played all day without gluing it in and was fine.  
Here is Hs5 pic of rolling bucking over installed hop.

Hs5 sells 3 rubbers for $12 shipped.
http://hsarmory.webs.com/productsandservices.htm