King arms Sig 556 hop spacer

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LazzurusMan

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Desperately need a new hop spacer as mine I believe is the cause of a massive FPS drop from 345 to 280. I've tested in many different ways and it's the only place I'm getting air leaks. Anyone know where I can get one? There's a guy on shapeways but it's like £30-£40 with shipping from the US.

 
do you mean something to force the hop unit up against the gearbox?

you can use springs or o rings round the barrel in front of the hop to get it nice and tight.

 
They don't act as a seal.  They act as a spacer.

The seal is created between the lips of the bucking and the air nozzle, and the air nozzle and the air tube on the cylinder head.


Did you replace the air nozzle (it might be too short).

Did you replace the bucking? It might have crimped lips, or lips they don't like the sig air nozzle.

 
Nozzle isn't replaceable, it's another king arms sig556 unique part. I did change the bucking. Might look into getting ANOTHER bucking then.

 
What bucking did you use?

I don't know how tech savvy you are. If it were my gun I'd rebuild it from scratch.

Gearbox stripped, new seals, new spring if needed and a full compression and leak test.

Hop unit fully rebuilt and pay attention to the air seal of the unit, and the fit of the bucking to the air nozzle.

Once that's all done rebuild.

It's a long process made more difficult by the fact the 556 isn't a gun you can just buy parts for.

 
I've stripped and rebuilt at least three times now, twice with upgrade parts for the gearbox, once to replace all seals.

She's apparently up to 300fps after a test last night, so I'll see how she does at Sunday's skirmish.

 
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