HPA inconsistency on a GBB Pistol

[Krisz]

HI!

Sorry in advance if someone asked it before but it's just so disappointing and can't find any solution on the internet. I've got a brand new HPA kit and a VFC Glock 45 and the fps changes a lot. On 90 PSI it shoots ~300 fps and then drops to 250-260. Any suggestion? 

Ty.

 

[Tommikka]

Does it shoot 300fps on the first shot only from fill, or 300fps on the first of a few shots?

Eg 300, 250, 250, pause, 300, 250, 250?

 

[Krisz]

Does it shoot 300fps on the first shot only from fill, or 300fps on the first of a few shots?

Eg 300, 250, 250, pause, 300, 250, 250?

First fews shots are 300 and then drops a lot like 250-260 and it doesn't go back to 300 at all.

Gas route seal could be the issue? Because it looks like a TM/WE style on the adapter but VFC gas route seals are way bigger. 

Cheers