Trying my hand at R-hop...

So I had some free time today and decided to try my hand at R-hop...

I have been intrigued for awhile by this; there are demonstrations of 300 foot shots (>400 fps though) on YouTube now, so it seems valid.


I wanted to use the Firefly flat nub but there are none to be found. I am too impatient to wait for R-hop patches from HS5 armory so I am making my own patches and hop nub. I am using windshield wiper vacuum line hose from Advance Auto (get a ton of it for $3), with 6 mm inner diameter. This is going in a stock KWA M4a1, with a 2gx bucking (got an extra and cut the fins out of the inside). It does ~400 fps with .20 gram bb's; the 2gx was good out to a measured 200 feet of total range out of the box, but the performance has degraded somehow, so I don't feel bad butchering the original bucking.

I made a jig to hold the patch while shaping it with the file (Ace hardware carries a ~6 mm round machine file), as seen in this video:


The guy in the video above uses brass pipe with an appropriate outer diameter; I used a piece of the plastic tubing that aftermarket inner barrels come in (used a plastic tube from a Systema barrel, cut in half with Dremel cutoff wheel). I used a dot of CA glue to hold it in place while I filed it. Advantage of clear tubing is that you can see it from all angles as you work.


Pic taken while CA glue is drying (brushed on some glue externally to hold patch in its final position)...


Finished look down barrel:


My flat nub isn't pictured; the profile is a little too aggressive at present because some degree of hop is always on, even though the R-hop patch fits the inner profile of the barrel fine.

I tested this afternoon with KSC .25's, and the grouping seems pretty nice; even at 'off' position there is enough hop to send a .25 skyward past ~125 feet. I think .28's or .30's will be ideal, and the patch may 'wear in' a little and even out some I think. I hoping to be accurate to 200 feet and be able to harass to 230-240 ft at this power level (still field legal everywhere). I will test with measured distances (yard tape) once I get some heavier bb's. If it works out ok I'm going to do this to my CQB/R as well.

Any of you all have any experience with this?

Yes, I use to use flat hop a bunch, you can get a decent 220+ feet out of a sub 350 fps gun. More recently, I'm experimenting with that cheapo tubing from mcmaster, much like a Rhop, but not quite the same. I'll see how that goes.

What is...."R-hop"??? Never heard of it before. What does it do?

Search it. It is a patch that provides backspin, which lets you use the bucking only for airseal. It is pretty good at its job. It takes some work, but when you get it right, it's pretty epic....and you can but them for 4$ each. If you want the knockoffs, they can be theoretically had for 1 cent each.

r-hop is a flathop mod. the mound on the bucking and alignment rib are shaved off and bucking rotated 180 degrees to get a flat surface. the r-hop or whatever material fills the shape of the hopup window on the barrel. this surface gives a better contact patch than with standard hopup mounds. the nub needs to be either modified or an SCS type H-nub used. works great for extended distances, but still gets affected by wind.

note that the barrel alignment groove needs to be filled and barrel/hopup arm stabilized.

-a|ex wrote:r-hop is a flathop mod. the mound on the bucking and alignment rib are shaved off and bucking rotated 180 degrees to get a flat surface. the r-hop or whatever material fills the shape of the hopup window on the barrel. this surface gives a better contact patch than with standard hopup mounds. the nub needs to be either modified or an SCS type H-nub used. works great for extended distances, but still gets affected by wind.

note that the barrel alignment groove needs to be filled and barrel/hopup arm stabilized.

Good job elaborating. He pretty much said everything, I'll just add in that some scs/flat/r hops are better than others. It's actually a pretty linear relationship IME (lol), with the time you spend on it, and your results. Meh maybe it's more like a square root function. Go Math!!