PapayaSalad Posted November 11, 2010 Report Share Posted November 11, 2010 Will a standard AEG hop up rubber work? Also, has anyone experimented with installing a nubbin piece yet? Maybe a custom made one? Nope, the KJW M4 hop up rubber is completely proprietary. There's no nub either. The rubber has a mound/nub that's already "built" into it. Quote Link to post Share on other sites
WTF?Shane Posted November 11, 2010 Report Share Posted November 11, 2010 Anyone else try swapping hop up rubbers to fix their hop issues? After changing hop rubbers, I noticed that I was getting much more consistency with my hop up. No more droppers and I can easily overhop .25s on the 4th and 5th setting. This hop up mystery keeps getting more and more frustrating...but hey, this is what fixed mine. Which hop up bucking are you using? Replacement KJW or RA-Tech? Quote Link to post Share on other sites
PapayaSalad Posted November 12, 2010 Report Share Posted November 12, 2010 Replacement from KJW. Quote Link to post Share on other sites
DesertFox Posted November 12, 2010 Report Share Posted November 12, 2010 is the ra-tech hop up rubber any better than the stock rubber? Quote Link to post Share on other sites
weekenny Posted November 12, 2010 Report Share Posted November 12, 2010 Not heard of anyone using it but from a picture I've seen it looks like the nub/bump on the outside is larger than the stock one and also square. Quote Link to post Share on other sites
DesertFox Posted November 13, 2010 Report Share Posted November 13, 2010 Wonder if that would fix people's hop up issue, bigger engagement point for the hop up arm = more hop. Quote Link to post Share on other sites
Roman! Posted November 13, 2010 Report Share Posted November 13, 2010 I have yet to take the hop up out yet, but that is my theory. That the engagement point of the hop up arm is not enough, uneven or some combination of the two. That is why I was wondering if a nubbin could be added. That would allow the hop up arm to press the nubbin and not the rubber. This might create a good even contact point. Of course, that idea is shot down by the reality that the hop up on a KJW does not use a nubbin. So never mind! I am intrigued though by the use of a square contact point on the Ratech hop up rubber. In my theory that seems like it would allow more/more even contact between the rubber and the hop up arm. OTH it might be worthless. Then we have papayasalad who swapped out the factory installed hop up rubber with a KJW provided replacement. That seemed to correct his hop up issues. That might be a clue to a cure , but until more people try it with before and after testing who can say? I need a couple of spare parts anyway and I think I will include an order for a new hop up rubber also just to see if there is a difference. Quote Link to post Share on other sites
weekenny Posted November 13, 2010 Report Share Posted November 13, 2010 Ra Tech rubber Quote Link to post Share on other sites
WTF?Shane Posted November 14, 2010 Report Share Posted November 14, 2010 Has anyone else had the RA-Tech NPAS valve strip on them? I had mine adjusted to shoot 390FPS for the past 2 days, then as I chrono it this morning it consistently shot 470FPS. After opening it up, I found the disk part of the valve closed shut while the set screw was still protruding like it was adjusted. Most likely gonna buy me a replacement and backup. Might even try out the Cradle velocity reducer. Finally got to shoot somewhere further than my backyard and find out there is no or very little hop adjustment. Will definitely try out the RA-Tech hop up rubber as it looks like the larger nub would do better. Quote Link to post Share on other sites
GismoBE Posted November 14, 2010 Report Share Posted November 14, 2010 @ Roman: I allready tried that, it's ok for a 100 shots or so, then it starts to move. Also it has to be in a very very exact spot, otherwise you get loss of velocity and/or jams. Quote Link to post Share on other sites
Roman! Posted November 15, 2010 Report Share Posted November 15, 2010 GismoBe, thanks for the heads up man! You saved me some heart ache. I think I am going to order a Ratech hopup bucking just to run a couple of simple tests. Meanwhile, I keep my fingers crossed someone will make a break through with a solution. Quote Link to post Share on other sites
Kai_Wolf Posted November 15, 2010 Report Share Posted November 15, 2010 I just ordered an RA tech rubber, Ill post what I find as well. Quote Link to post Share on other sites
Shadow_Ocelot Posted November 16, 2010 Report Share Posted November 16, 2010 Kai how much did shipping run you from RA tech? My theory on the hops is that with time they all die. Mine was working fine out of the box, but after about 5-6 games now is dying down, whereas my buddy bought one used and it was never the greatest. I might pick up a bunch. Quote Link to post Share on other sites
WTF?Shane Posted November 16, 2010 Report Share Posted November 16, 2010 Kai how much did shipping run you from RA tech? I know this question is going to Kai, but I purchased one earlier this morning as well. Airmail (8-10 business days) is $9 but express mail (4-5 business days) cost me around $28. Definitely stack up on your order. Quote Link to post Share on other sites
Kai_Wolf Posted November 16, 2010 Report Share Posted November 16, 2010 I chose the 9 dollar shipping. Total was 16 dollars or so. Quote Link to post Share on other sites
t_hum Posted November 17, 2010 Report Share Posted November 17, 2010 A few observations myself and a few customers have made recently regarding the hop issues... The stock KJW barrel has a hop window width of .147". The Madbull barrels I sell are .165" and other brand AEG barrels are pushing .176". Several customers are reporting that they get better hop, or in a very few cases overhop, with the tightbores (which have that wider opening width.). Im starting to wonder if the hop window on the stock KJW barrels is too narrow. Rather than the nub entering the barrel its being stopped by the edges of the window making hop ineffective. This could be from inconsistent widths on the barrel itself or inconsistent dimensions of the hop rubbers. For someone with a stock barrel on hand that is having terrible hop it might be worth trying to widen the window slightly to see if that solves the issue. I dont have my stock barrel on hand otherwise I would give it a shot myself. Quote Link to post Share on other sites
GismoBE Posted November 17, 2010 Report Share Posted November 17, 2010 Hum, are that normal AEG barrels that fit into the KJW? I got several PDI's, Deepfire's and prommy's here. Is it worth the try? Quote Link to post Share on other sites
t_hum Posted November 17, 2010 Report Share Posted November 17, 2010 Normal barrels do not fit without advanced modification. Quote Link to post Share on other sites
GismoBE Posted November 17, 2010 Report Share Posted November 17, 2010 I was afraid of that answer.. I'm doubting very hard to keep this one.. There simply are no aftermarket's, apart from Ra-Tech and some US manufacturers. I can get a G&P WOC M16A4 for 300 euro.. So I'm kinda doubting here... Quote Link to post Share on other sites
t_hum Posted November 17, 2010 Report Share Posted November 17, 2010 Keep it! The WA platform falls far shorter than the KJW. You will spend that 300 Euro twice again over to have a skirmishable rifle. I am Cradle Airsoft, btw. If youre not happy with the RA-tech reducer you should take a look at the one we make. It should work without hassle for the life of your gun as the users here can attest to. The community will have the hop issues sorted very soon I think. After that, there is no reason not to own one. Quote Link to post Share on other sites
DesertFox Posted November 17, 2010 Report Share Posted November 17, 2010 Not much aftermarket support is needed for this gun, stock parts are readily available. Everything else is provided by T_Hum I feel like were getting so close to getting to the bottom of this hop up issue. Quote Link to post Share on other sites
GismoBE Posted November 17, 2010 Report Share Posted November 17, 2010 Yeah. I hope they're going to make some aftermarket externals quickly. The hopup is irritating. I'll check ur shop out, I'm happy with the RA-Tech reducer though. it works pretty good and I can't see how it can break. :-) Quote Link to post Share on other sites
GingaNinga Posted November 17, 2010 Report Share Posted November 17, 2010 T-Hum, I am using your custom cut barrel and having the hop-up issues. Just thought I would put that out there Quote Link to post Share on other sites
t_hum Posted November 17, 2010 Report Share Posted November 17, 2010 Thats definitely worth noting. Maybe the problem is more related to the rubbers then? Im interested to see how the tests on the RA-Tech rubbers turn out. Quote Link to post Share on other sites
koolaidz830952 Posted November 18, 2010 Report Share Posted November 18, 2010 First post on Arnies~ I know I don't have any credibility here in particular, though I am a regular to another forum, and this being my first post will make me seem like an absolute n00b; so please excuse the following. I know my answer might already be in this thread, but I hope you understand the my inability to read the 100+ pages. Again, excuse me if I'm being annoying, hopefully I'll become a regular here eventually. I finally have the funds to supply myself with the RA-Tech Custom KJW M4 and I just wanted to get some opinions from the KJ M4 experts. Do you guys think it is necessary for me to buy the RA-Tech custom? Or would I be better off just buying the stock KJW from eHobby or something? Also, is there anything I should look out for when first receiving the KJW M4, like common problems that can be fixed easily. Any tips that would prolong the life of the KJW would be nice too. Oh and one last thing, to those who are in the US, have/did you had any trouble getting in the KJW M4, or any GBBR, to pass customs without a hassle? Thanks Again, sorry for my ability to seem like a complete n00b and be annoying. Quote Link to post Share on other sites
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