Hop unit tight or not?

[CrispyB]

Hi, I'm new to airsofting, but I'm the sort of person that likes to fiddle with how things work and make things better. I bought an Ares AM 008 and it was awful straight out of the box. No range and awful power. Turned out there was a tear in the standard bucking. 

I put an Asg M105 main spring in it with a bearing spring guide. I have also fitted an SHS Cnc hop unit with a Maple Leaf 60 degree bucking and omega nub. 

My question is that the new hop unit is so tight in the upper receiver (to the point that I need to use a flat blade screw driver to prise it back out). Should it be that tight or should there be a slight be of play? 

After all the spring on the inner barrel and the one on the front of the hop unit are doing nothing because of how tight the side tabs of the Cnc hop hold the unit in the upper receiver. Do I need to file any metal of the side tabs or not? 

Please help😬

[Enid_Puceflange]

Personally I wouldn’t worry about how tight the hop unit fits

Its something that you would want a snug fit with anyway to avoid movement

[Adolf Hamster]

as long as it's not so bad that you're damaging it (ie bending) when fitting, then it can be ok.

 

the key is that the hop unit is up tight against the gearbox, typically for an m4 variant this is done either with a spring or series of o-rings around the inner barrel to actively push it back against the gearbox, this has the added benefit of reducing wobble between the upper/lower.

 

on other designs, the hop unit is sometimes bolted to the gearbox solidly to prevent movement.

 

so as long as you don't have the hop unit sitting too far forward on assembly (ie that there's a gap between it and the gearbox) then it being tight shouldn't be an issue.

[Skara]

It's another certified Ares moment.

Hop units are supposed to be on the loose side, so that the spring(s) can press it against the gearbox casing.

Filing the hop unit can be tricky as if not done correctly it may lead to alignment issues, you may end up with the unit slightly tilted to the side.

 

When I had mine, I kept the stock hop unit and modified a tensioner to fit inside, granted I had a flat hop, not a maple leaf but the concept still applies.

[EDcase]

Ideally the hop unit should be able to move in/out a bit on the spring at the front. 

This ensures a good seal with the nozzle while allowing some movement margin in case of a miss feed so it doesn't damage the nozzle.

 

The main thing for performance is to make sure the hop unit makes a good seal with the nozzle when in the extended (firing) position.

But if the hop unit is too far back (from the front of the gun) it will put a lot of strain on the tappet plate in the gearbox and something will break.

 

 

Edited August 26, 2022 by EDcase

[Rogerborg]

1 hour ago, EDcase said:

Ideally the hop unit should be able to move in/out a bit on the spring at the front. 

 

But wh...

 

1 hour ago, EDcase said:

This ensures a good seal with the nozzle while allowing some movement margin in case of a miss feed so it doesn't damage the nozzle.

 

... oh.  Fair enough, good point.  Although it won't move by 6mm, so I'm not sure what sort of misfeed it would protect against.  A fragment of BB?

 

 

 

On 23/08/2022 at 17:02, Adolf Hamster said:

the key is that the hop unit is up tight against the gearbox

 

It's only going to be shoved in as far as the gearbox pushes it during assembly, and won't work forwards as there will be some spring tension against it, so it should be fine.

 

I'd still wave a file at it though.  It's airsoft, nothing is standard, and once you start mixing and matching, the onus is on you to make it all fit.