FX Dream Tac and .22 Redesing pellet help

[Flyer1944]

I have a Dream Tac .22 bottle version with a power plenum and would like to shoot JSB Redesing pellets at or above 900fps.i have raised the reg pressure to 150 bar and maxed out the hammer but with these settings am only able to get to about 877fps .any help would be great or am i expecting to much from the gun?

 

[Dairyboy]

What length barrel do you have? I'm guessing your asking a bit much from it.

 

[Flyer1944]

I have a Dream Tac .22 bottle version with a power plenum and would like to shoot JSB Redesing pellets at or above 900fps.i have raised the reg pressure to 150 bar and maxed out the hammer but with these settings am only able to get to about 877fps .any help would be great or am i expecting to much from the gun?

I posted my question twice in the second I said it is a. 600mm barrel bottle version it has no other add on parts

 

[Vetmx]

You might also be running out of enough hammer weight at 150b.