[Mental96]

Hey good people.

Ive opened up my v2.5 to upgrade/mod some stuff and even though the stock PH sealed 100% in the cylinder, I had that SHS PH and though it could be better for a DMR to have a higher mass piston assembly, plus the double o-ring head could seal better, no?

Wrong!
The Shs head could not, whatsoever, create compression in the cylinder. Luckily the stock ph sealed perfectly so im back to that.

Could a brand new head have a bad oring ( seamless o ring) from factory? Or does it need break in?

 

[csakip]

The seal also depends on the cylinder. If it is bigger than the one the SHS piston head has the O rings set up, it won't seal. Get a bit bigger O ring to see if it works. If there is big difference between the diameters of the piston head and the cylinder, even if the O ring seals, it might be squeezed to far into the gap, slowing the piston and loosing power. Rarely, but it can happen.

But usually don't fix what's not broken.

 

[Mental96]

Thanks for the input mate.
Yeah I shouldnt mess with something that works, but got it for free so thats a good reason alone..hehe

I really dont know if the A&K cylinder has wider bore than other v2.5s so thats probably a fair enough excuse for the lack of compression, although the SHS PH did fit snug against the cylinder walls so I thought its weird not giving any compression when tested it.

Hmm...Could it be that some silicon grease from overlubed cylinder walls/PH o-ring end up inside the PHs air ports and clogs up the exhale process of the pistonhead's ports? That could interfere with compression, no?

 

[csakip]

The A&K M4s have bore up sets by default, IDK if the sr25 is bore up or not.

 

[ArcAngel]

The A&K M4s have bore up sets by default, IDK if the sr25 is bore up or not.

its not. its standard. But the CA bore up set works BRILLIANTLY in the A&K