Tuning issues with regulator

[Barzor]

Hello again folks been doing some tuning with my .177 pp700sa. I ordered huma reg and just rec'd. I want to be able to shoot slugs and I think I'm almost there but almost but maybe not. Ok so I put the reg in and I put it at 145lbs. The hammer spring screw used to be flush and now I screwed in 3/4 of the screw is covered or down, there is just enough to barely turn with wrench. SO I filled the tank right at a line before it turns red 20bar. My first shot is only 469fps then slowly by 10 shots im at 500fps. The gauge has hardly moved. Velocity keeps going up, by 15bar im at 600fps and climbing and this time at 25 shots. Around 32 shots im hitting 700fps and it hovers there until 40 shots then it starts to go down finally and I stop at 45 shots and at 650fps. At this point im at 10bar. Im shooting JSB match beast at 16.20gr.

How do I get more of a straight line with the higher velocity rather than a hill of starting very low then going up to the very high.

When you put the reg at a certain value is this where I should fill the tank to to get consistent shots? I have no clue. I hope someone can help? Should I lessen the tension of the hammer spring or should I increase the reg?

 

[Florida_Man]

For your given reg setting, start with the hammer spring low, then increase it by 1/4 turns. Record the speeds. Eventually they will plateau or go down, that will give you what your gun can handle at those pressures

 

[elh0102]

For your given reg setting, start with the hammer spring low, then increase it by 1/4 turns. Record the speeds. Eventually they will plateau or go down, that will give you what your gun can handle at those pressures

Good advice. Using this method, if you don't reach a velocity as high as desired, then you need to increase your reg set point. If the maximum is more than about 110% of your goal, then you can decrease the reg for a more efficient tune. If you are going by the scale on the reg, be aware that it is often not very accurate, so you might not really be set at 145 bar. And to answer your fill question, no, you should fill well beyond the reg set point, otherwise the rifle is essentially unregulated.

 

[Barzor]

Thanks guys