fx crown standard liners

I have a .22 Crown blue laminate with standard A liner and 500mm barrel. The most velocity possible is right around 840 FPS with eh JSB RD Monsters. Accuracy is OK, but nowhere near as good as with the 18.1 grain JSB Heavy pellets. I have a B liner, specifically supposed to work best with the RD Monsters, but haven't tried it yet. I will want to make modifications to the gun in order to get at least 880 FPS from the RD Monsters with the B liner. I have no intention of getting a new 600mm barrel kit. But a heavier hammer, increased barrel transfer port diameter and perhaps even a larger valve are in the cards...
 
Do you mean in the 600mm B liner? there is no 600mm pellet A Liner is there? certainly not here anyways, maybe only Australia?

I have tried the 25g Monster redesigns with the 600mm B liner in the Crown and the Impact, velocity was maxed at around 860FPS, accuaraccy was okay but not overly exciting at 25 yards.

Pushing the pellet through the liner leads me to believe it is too tight in the barrel, either this or the .22 transfer port (or both) is limiting the velocity, as expected you get slightly more from the Impact than the Crown.

Certainly as above and not very promising is that the 18.13 seems to perform better than the pellet the B liner was actually designed for!
 
I have a .22 Crown with 500mm A liner. It shoots 18.1s better than 25.4 RD Monsters. Much better. The fastest I can get with the 500mm A liner and 25.4 grain RD Monsters is 840 FPS. I want to get at least 880 to 890 FPS. I have a .22 B liner 500mm, and I have not tried it yet. FX says it was designed for the 25.4 grain RD Monsters. I will wait to try that until I can get the velocity on my gun up to where it needs to be to shoot the RD Monsters. Not done yet. Will probably need heavier hammer, enlarged barrel transfer port and perhaps larger firing valve. I hope that explains it better...? ;)