The J-Hop Testing Thread

Ok folks, I tried this, rather scepticaly, on my scout M14 with 18mm length barrel window, shooting at 347fps w/.2.

I used some 6mm brass tube, bought from the local DIY store, as a filler piece.

I inserted the tube into the barrel, and then using a #1 size model brush painted the exposed tube in the window with silicon grease, being carefull not to get any on the barrel window edges.

As 1 of my trades is a plumber silicon sealant isn't a problem to find..... so I applied a layer of Dow Corning 781 clear silicon sealant to the window and pushed into place/shape with my finger, then with plenty of good old fashioned spit applied to a straight edge I tooled the top so that it was flat and level to the profile of the barrel.

I left this to cure over night and then the following morning I carefully removed the packing tube, to allow the inside to cure thouroughly. When this was cured I cleaned all the grease from the inside of the barrel and reassembled the hop etc.

Tonight I got round to trying it out and initial tests show good results on lift, shot consistency and accuracy. How it will stand up to repeated use and high fps I have yet to test, but given that it now only uses the rubber as a nozzle seal and to hold the silicon 'nub' in place, I see no reason as to why it shouldnt last a fair while :shrug:

1 thing I have noticed is I've lost approximately 10 fps, I can only put this down to the extra drag being created by the slightly softer and stickier surface the BB now gets dragged along :shrug:


To my mind there is only 2 things you need to get spot on, and those are internal smoothness and the external uniformaty in thickness, as they are the only things that are going to adversley affect hop performance

@ Milsim..... a flat hop refers to the R and ER style hops or any other method that you use to create a long flat pressure pad to hop the BB.


@ all of you..... after being in the plumbig trade for the better part of 25 years I've leant that the best lube for moulding silicon is spit, but for gods sake don't put the stuff in your mouth, it tastes like sh1t and its none to healthy for you! Always wipe your finger, or tool of choice, clean before going back in for more spit, and dont be affraid to use plenty of it, the more you use the better it will not stick to the silicon.

There is an alternative, which is ''almost'' as effective, and that is a strong mix of washing-up liquid and water, which provides almost the same libricative qualities as spit, but not quite :tup:


Gona try this in my VSR in the near future to see if it will stand up to higher fps and maintain the same level of accuracy it currently possesses :yup:

Sorry kids, I should of posted this earlier but thought it a dead idea, as even I have sort of moved on from it :shrug:

These are some pics I took of my test hop in my M14......





As you can plainly see their is an arseing gert hole in the silicone, this I believe was caused by the BB dragging past the harder edge of my hop nub to the point of pulling chuncks of the silicone away :shrug:

Please bear in mind this is high grade building silicone, not the cheap shit you can buy for buttons down pound land/ dollar store.

If it does this to high grade silicone its definately going to do it to other, less durable products.

As an idea this method is sound, and to be honest its ok in use in the short term, as for a long term item I'd give it a miss and try some other more durable ( read harder) rubber, which I'll suspect will then not give the same grip that silicone gives :shrug:

To be honest the whole molding process, hap hazzard and inconsistent results on BB flight from the moulding is to much of a ball ache to warrent to much time and effort being expended on it :shrug:

It may well do, but there are far more easier ways to achieve better results in a shorter time :shrug:


The pics there are of my third attempt at even getting it to shoot straight, and when you add in the time of moulding, cureing and finishing each one, a process that that takes a couple of days at least, its just easier to make something else work :shrug:


I still use the basic principal in mine but I now embed actual hop rubber into the silicone as a friction surface and use the silicone as a bonder and sealer in 1, I also bond my hop rubber to the inner nub and barrel at the same time.

I do all this over a special former a spacers that I make to each barrel to ensure a perfect fit every time.


As to the original version of the J hop, like I said, a good idea in theory, I just dont think it met with my exacting standards :shrug: where it might meet with someone elses :yup: