Tuning FX Crown Pressure Increase = Speed Drop

[Honoo]

Hi

My crown shoots JBS MKII .25 great at a very consistent ~820 fps with reg pressure at 130. Any increase to the reg pressure would cause the speed to drop drastically to around 720.



Any ideas what is causing this? Hammer not hitting hard enough? Or reg problem?



Thanks

 

[TMH]

Generally caused by hammer no longer having a strong enough impact to open the valve efficiently, due to higher pressure.

Is it a Mk2 Crown? In my experience they seem to like a bit lower reg pressure as compared to the Mk1's.

Increase hammer spring tension and/or increase hammer weight. Above 130 - you are also getting closer to the Crown's maximum regulator pressure of 150 bar.

 

[Honoo]

Generally caused by hammer no longer having a strong enough impact to open the valve efficiently, due to higher pressure.

Is it a Mk2 Crown? In my experience they seem to like a bit lower reg pressure as compared to the Mk1's.

Increase hammer spring tension and/or increase hammer weight. Above 130 - you are also getting closer to the Crown's maximum regulator pressure of 150 bar.

It is a first gen crown with a huma reg (not the high pressure version). What I find strange is that it is at 130 and I am only getting 820 fps. Is that ok? Thiught I should be getting around 920 or so



I wil see about adjusting the hammer further. 

 

[Long_Gun_Dallas]

Hammer not hitting hard enough. You should see gains to maybe 145 bar? Maybe a touch higher. For me, in .22 the hammer doesnt do much for me above 135 bar. Until I add weight. But more initial pressure doe seem to help heavier/larger projectiles. I know the .30 guys tend to run 145-150 bar.

 

[B]

What they said, definitely not enough hammer weight.

B