Aug Gearbox Moves!

[Trixxeo]

My CA AUGs gearbox likes to move backwards, thus breaking the air seal and losing all performance. 

Just wondering what people have done if they've had the same issue. short of drilling a hole and pinning it through!

[Archer]

Had a similar issue with my JG AUG.

 

I glued a washer onto the black retaining plate that holds the gearbox in place. 

 

It pushes against the gearbox and keeps it in place.

 

Either use washers or a something like a 2p coin depending on how much distance is needed.

[Iceni]

Your barrel is wrong then.

Let me guess you've shimmed the barrel so it's locked in place, or the hop unit doesn't move freely on the sping system (or all the way back). Do not shim the gearbox you'll crack the magwell plate.

I'll add more to this later but I have to go to work now. For the minute just look at the hop, and the plastic parts that connect the hop to the inner and outer barrel. Either a retention screw is touching the inner barrel, or you've shimmed the barrel and it can't move. It's the movement of the hop that locks the gearbox in place. You may have also put the brass ring in the wrong place when you built the hop, so it's not allowing the hop/barrel assembly full movement.

Edit time

 

Right that's a lonex style hop unit, I used it for the image simply because it's not all black, the plastic Black one you have should be identical.


First thing to do is check you have all the parts. The gearbox spacer is vital, It locks on in a pretty loose fashion and if lost then the gearbox will not engage the hop correctly. This part fits on the hop after the hop adjust dial and just sits on 2 prongs and locks with a 90degree twist. New hop units usually ship with this part so if lost it's less than £5 for a complete new hop unit.

You should also have a brass ring that is not in the image.

People more often than not will put the ring into Position A. This means you have less space for the screws that hold the hop assembly into the outer barrel. Often if built with the ring in position A you will find the hop will not move on the spring, The screw slot is what holds the barrel and hop in place not the screw touching the barrel. It's a common mistake. The 2 screws that hold the hop should not touch the barrel at all, and should allow the hop unit to move in and out just on the spring pressure.

Personally I cut my Hop rubbers down a little and put the Brass ring into position B. This gives a little more space for the Screw slot screws. And doesn't affect the hop performance if you are careful with the cutting of the rubber. You will need something thin and moderately flexible to get the ring into the hop A little gentle poking about and it should sit just nice. Make sure the ring is fully hidden so it doesn't upset the C-Clip.

The C-Clip should sit flat in the Hop unit. Badly fitted rubbers will cause this to be very hard to get in position or even try to pop out a little. If this is happening it's your choice of rubber causing the issue, or you have trapped the rubber lips. If it's not sitting flush then this will also stop the hop assembly moving correctly and cause problems with the gearbox.


With the hop build right, The unit moving correctly, and the spacer in place you should find the gearbox is pushed back correctly. As it's the spring at the front of the hop unit that provides the pressure to keep the gearbox in place, and provides the pressure to keep the take down pin in the middle of the AUG tight. When you assemble the upper to the lower you should be able to feel the hop touch the gearbox, then have to push a little to make everything seat. If the AUG just slots together with no pressure then you can guarantee the hop unit is what's causing the problem.


Hope this helps