FX ST-X 500mm "B" liner for .22 Crown

Let me explain my intentions or goals. What I want to do is get my Crown shooting the .22 JSB RD Monsters at a high enough speed for them to be accurate like the Daystate Redwolf HP. The RW HP has them shooting somewhere in the vicinity of 950 fps, plus or minus 20 FPS, and they were very accurate at EBR this past year, winning the Pro division and the AFT Sniper Class. I have my Crown shooting lights out with the JSB Exact 16 grain at 25M and 50 Yards, (930 FPS), but I want to have the option of shooting the 25 grain RD Monsters when it gets too windy for the JSB Exacts. I know with the "A" liner, I can get the 18 Grain JSB Exact Heavy to about 960 FPS, and the RD Monsters to about 840 FPS with the current stock Crown set up.

So, I have a "B" liner (supposed to be designed for the RD Monster) which I haven't used yet, and I have not added a hammer weight, or increased TP size or port size on pellet probe, or increased the valve size. From what Ernest tells me with the 500mm barrel, the most I'm probably going to get out of it with hammer weight and valve mods is around 880 to 890 FPS. I'm not sure how accurate this will be, but I want to do this prior to stepping up to a 600mm barrel. I have the AMP regulator in mine, so jacking up the reg.. pressure past 150 bar if necessary shouldn't be a problem. 

Does anyone have any experience with the Crown 500mm B liner in their gun? Or perhaps some advice (and not "get a longer barrel")?. ;)

Thanks much, Mike
 
Nah, he's shooting the 600mm STX slug liner... I'm not going to really head in that direction at this time. I have my own opinions of slugs, and for numerous reasons will continue to use pellets. My .22LR Savage Anschutz Sporter can shoot circles around any non-big bore air rifle at any distance, plus the ammo is as cheap or cheaper than air rifle slugs... Don't want to get into arguments about this, just wanted to cut off the "why don't you like slugs" questions in advance. ;)
 
Trying to do exactly the same as you albeit from a different direction. Got all the mods on my Crown, still can't get past mid 800's with the 25's (500mm).

So Impact and 600mm B pellet liner, .25 TP used, reg at 150, 15mm hammer gets me to 930 FPS with 50 shot count.

Ken at SPAW is getting 970 with the RW HP, out with one tommorrow which is doing 875 from the factory, we shall see how the accuraccy fairs at 100 yards.

Can't see the point of slugs either personally, .22 rimfire barrel fitted to an airgun and Eley bullet heads at a few cents each is the way to go!