Mk18 Overhaul - Bit of a Fail

[Zarrin]

I would imagine @Davegolf is correct about it being another variable that could effect the fps slightly.

But I mean on the same or even greater merit it could be any of the below:

- the spring guides which could have a different thickness of bearing washers,

- the air seal of the entire piston/cylinder/nozzle section

- the hop components. Mk18 has a soft rubber flat hopped inside the red metal ZCI hop unit, and the MP5 has a macaron/omega set in a bog standard JG hop unit.

The answer is probably in there somewhere ? 

 

[Adolf Hamster]

thrust bearings for sure will do it, you can even add shims to adjust a little bit. normnally i just run one on the spring guide and not the piston.

air seal for sure, hence the discussion about static/dynamic airseal with regards to the porting (although you really want voluming to be correct on the build regardless)

normally i'd blame nozzle-hop, as it's much more of a bugger to check than the rest of the system (ie you can be pretty confident by testing the rest of it is right) often its a case of the hop unit sitting too far forward (especially in guns where the hop unit is bolted into place)

 

[Zarrin]

thrust bearings for sure will do it, you can even add shims to adjust a little bit. normnally i just run one on the spring guide and not the piston.

Yeah, I've built and tuned bearing spring guides out of the old one piece ACM steel guides before - very good way of tuning fps actually, you just gotta make sure that the piston will allow any mods you do to pass through freely otherwise you'll get a lockup very similar to what I had with the above case.
 

You actually got me thinking though, you could probably tune fps by injecting hot glue into the piston ? 
Maybe lather the canal up with some silicone grease beforehand so you can pull the newly formed rubbery plug out if necessary - but I mean that would probably work tbh ?

 

[Adolf Hamster]

not sure how comfortable i am with the words "hot glue", "piston", "grease" and "rubbery plug" appearing in the same sentence.

and it's not just from a purely technical standpoint.....

 

[Zarrin]

not sure how comfortable i am with the words "hot glue", "piston", "grease" and "rubbery plug" appearing in the same sentence.

and it's not just from a purely technical standpoint.....

Hehehehe ?

Mate from the purely technical stand point it's bloody genius!  Bagsy, not the one to try it out first! ?