Did everyone resolve their cycling problems? My problem came back even though everything is super tight and hop up is in position. I think it's crying for a cleaning and silicon.

Mine is cycling fine, Although the elastic needs replacing ALOT... Usually once a game day. It is shooting around 415 though and that could be the problem.

Anybody know where to get the top-down hop-up mod done?

I haven't replaced my elastic yet. What are the symptoms of a bad elastic? What happens to the elastic that makes it stop working?
I bought some spare parts from KJW this week including 2 elastics so I'm in luck.

I think just eventual wear, or sustained full auto. I find it usually snaps if I just empty a mag with no BBs to get rod of the propane.
I need to get some innertube, but the stuff I got from canadian tire was like 2mm thick walls and was not the right stuff at all.

When the elastic breaks you will be able to fire it but it will not cycle.

Yeah, it will most likely act like a bolt action, last time I broke one I had to rack the chargin handle each shot...

The outer lip of my RA-Tech red piston o-ring was bent and stopped my bolt carrier from working properly. All better now.

Hi,

I just got my brand new KJ M4 3 weeks ago (my firts GBBR but I'm used of assembling/modifying AEGs), after reading many forums, I installed the usual recommended by experienced GBBR users

Craddle velocity reducer
Cradle Piston
RA_Tech 6.01 380mm tightborre

I saw the video on youtube for installing the Cradle velocity reducer, everything went smoothly but after passing the M4 on the chrony I'm really disapointed...the fps are totally inconsistent !


with 1 small spacer + the o-ring, on the .25 (chrony set for 0.25g BBs ) it ranges from 325 to 420 with sometimes a few shots around 390fps but still really really inconsistent....same thing with 0.20g

I checked the velocity reducer many times, changed the spacers, checked that nothing was loose, well lubricated (not too much), cleaned the hop-up but still the same thing...after firing around 20~30 mags I'm really disapointed....any suggestion of what I did wrong ?

Is your barrel clean?

I can't figure out how to get the 3 small pins punched from the lower receiver. Whats the trick?

You have to remove the springs attached to them before trying to push them out, these springs are seating in groves just like a snap ring would, preventing the pins to go out the at undesired moments...

That's the only thing I didn't try, do you think it would make such a big difference ?

I would go to .28's or .30's ,I get better consistency on the chrono
and really good range.
I also did the "top down" hop up mod on two of mine. WOW I like :D

Are you using propane? No oil ? that's what mine like.

Thanks for the help guys !

I'll try .30 too then....yes I run it on propane with no oil...only a drop of silicone in the mags before and after a couple of mags...are you guys using something else instead of propane for better results ?

Hey Fab, acouple of things you should check is to make sure that your cradle piston is centered when installing it on the bolt carrier. Screw is loctite as well. Check the o-ring on the cradle piston for proper lubrication and seal. Unfortunately with gas guns you will get fps deviations of 10-50fps which will affect your shot to shot accuracy/range. Depending on you play style, the faster you shoot the colder your mag in turn it will affect range/fps. Lay off the silcone, clean your barrel and hopup rubber with warm dish soap. I suggest doing the Top down hopup mod if you want any kind of respectable range and consistency combo with a blue ra-tech rubber and barrel. And use .28-30's but you will have a problem with not being able to overhop them if you dont have the mod done.