FX Crown amp reg/new design (finding the IOP)?

[Air Head]

Hi all
Thank u for your advice when asking about the AMP reg on my FX Crown recently !

So i’ve had a fiddle, lol ,as recommended by you guys ,not sure on the results !

I have de-gassed ,started @ 48 on the reg then shot 5 shots over the chronograph ,power was low ,then when i increased the reg pressure by 2 bar to approx 53/55 ,the power in-creased low 760’ using 8.4 grain pellets,i believe this is the start of the power curve (knee) i could be wrong ?

I then increase hammer tension ,but the fps did not move much !
There was 1-2 FPS between shots ,over 10 shots so very consistent perfection lol

When i tested some -more ,increasing reg to approx 60-62 (hard to read on the fitted gauges) ! The Power hardly moved ,only when i increase the hammer @ 60/62 did i achieve the higher FPS ,but the variation /spread of the pellets are not as good as the lower setting of the reg @ approx 53/55!

The JSB 10.34 grain pellet is causing a problem ,as it’s very efficient in this gun ,so having to nock the power down to approx 700-710 for a safe sub 12ft lb !

In doing this i having to run the JSB 8.4 @ 760 and my best pellet JSB Express @ 780 !
So i’ve still got a small amount of creep on the reg as before ,i now know how to (or think so ) increase FPS !

So a couple of questions ,is the IOP the one i got on the start (knee) of the upward power curve 53/55 bar on the reg ?
The reg i tested to 60 with hardly any improvement ,and past that 60-65 power decreased !

Also not sure i have read this correct ,but does the RST ,reg set pressure need to be higher that the IOP?

call me confused please advise & i really do appreciate advise regarding this confusing subject !

Watched “Jeff Vid “sub12”,set his reg @ 90 ,on a mk1 Crown (possibly older reg),what’s that about ?

 

[BallisticBill]

The JSB 10.34 grain pellet is causing a problem ,as it’s very efficient in this gun ,so having to nock the power down to approx 700-710 for a safe sub 12ft lb !

In doing this i having to run the JSB 8.4 @ 760 and my best pellet JSB Express @ 780 !
So i’ve still got a small amount of creep on the reg as before ,i now know how to (or think so ) increase FPS !

So a couple of questions ,is the IOP the one i got on the start (knee) of the upward power curve 53/55 bar on the reg ?
The reg i tested to 60 with hardly any improvement ,and past that 60-65 power decreased !

The sensitivity to pellet weight is a characteristic of the gun you won’t easily change. Low plenum pressures favour the heavier pellet so you would have to modify the underlying power curve to raise the IOP.

Forget the "knee of the curve" and any Ernest Rowe videos you've seen as these relate to FAC and are unsuitable for sub-12, potentially leaving the gun in a state where it will run hot if the reg creeps. Use the 5-bar process instead.

Where you are at the moment, I think (not having seen the data) is your IOP is around 55-60 bar. The decrease in MV as you raise the set point to 65bar shows you are then above IOP. You really need to map this curve to be sure.

If you leave the setting at current level (?53/55bar) chrono a string as the gun comes off reg, checking there's no off-reg peak. Then fill the gun to max operating pressure and chrono a short string. If the MV when full and when just above reg set point are substantially different you are not at IOP... then come back for advice.

 

[Air Head]

Thank u ,the JSB have me unsettled as they are a bit erratic ,with there FPS!@ the higher reg setting 20 fps spread any thing from 702 -722

So i reset the reg @50 bar intending to work back up ,decided to (Only use /set with the JSB 10.34 ) and the reading 705 ,705 ,705 ,705 ,703 ,705 ,703 ,706,705 thought my chrono had packed up ,so 10 bar less on the reg ,tuned hammer up went to 710/12 after six turns ,so turned /decreased it back down !

Think i like the results

 

[BallisticBill]

You may have found the right setting by chance... or perhaps not. When you find the there's a drift in MV over the regulated string you'll appreciate a more systematic approach.

 

[Air Head]

Yes, not sure what this is ,looks very good ,but as u say needs more of systematic approach ,it’s appears to have settled those 10.34 ,i can live with them now ,but will investigate /shoot a bit more across the whole fill ,as much as possible ,the thing don’t use a-lot of air !lol

I have always liked the design of the JSB’s 10.34 ,but like the higher /faster speed of the express 7.9 ,but as i said can only run @ 770 or so ,as those pesky 10.34 start getting very close to the sun lol

 

[Air Head]

Just read the lane 5 step again ,and understand RSP is set higher to find the IOP when off the reg !
i’ve done it differently ,increasing the reg pressure and the chrono to find the FPS!
It’s going in slowly ,but i am learning