PSI / Bar, the PCP and maths midgets like me!

[camies 1]

Nice new PCP and the barrel is marked as a maximum fill pressure of 3000psi.

ok so far?

Pump calibrated in BAR and not psi.

So whats the conversion?

 

1 psi = 0.069 Bar

Easy for you maths buffs but for me, out came the calculator. So, knowing that I'm not alone at being bad at maths, here is a few conversions to save grey matter overheating.

 

1000psi= 69 Bar

1500psi= 103 Bar

2000psi= almost 138 Bar

2500psi= 172 Bar

2750psi= almost 190 Bar

3000psi= almost 207 Bar

 

Daystate say that you should fill to the pressure marked on the body. In my case that's 3000psi / almost 207Bar.

My friendly gunsmith pointed out that when I go rabbiting the most I let fly is 30 pellets so why pressurize to the max?

His reasoning is that running everything to its limits isn't necessary and after putting the rifle through his chrongraph, I'm inclined to believe him.

In practice that means I only pressurize to 170 Bar. The difference is only 20-25 fps from maximum. As I zero at 30yards anyway, it does not matter a great deal at 50yards.

 

Finally for you computer buffs, there is a website for conversions at http://www.onlineconversion.com/pressure.htm

 

Hope this is useful.

[mad al 146]

Excellent idea to post this as a lot of folk are confused by this issue and need to be aware of the pressure they are dealing with when filling a PCP. I fill all my rifles to 180bar as I find this works well for me and generally keep them between 150-180bar.

 

Thanks for the info

[Timelord 0]

At last an intelligent thread started on THL I mean I get fed up with the usual suspects like "what airgun" "what pellet" etc etc. I'm sure I speak for all on that one

 

Back on topic It seems that most PCP rifles are not regulated so finding the pressure that suits your gun so that the zero and power stay the same is a tough call. I had this with my old MK1 Rapid as there was a noticable power curve to each fill. It's well worth getting your guns regulated properly so your shot count is increased and the consistency between each shot is nearly the same. This will stop any issues with what pressure to fill your gun. On my S-TYPE with the 500cc bottle the recommended filling pressure 250 BAR= 3625.94 PSI and because it's properly regulated I get well over 500 shots in .177 caliber and the difference in FPS between each shot is negligible...

[ghillies 209]

ok, you'll luv this... nip to the shop and get a from max to whenever the shots drop off silly in power 'full chrono read out'..

 

then read off the fps varience and see where it's least, usualy a few shots in from the max fill, then see how many shots till the drop off occurs.. thats the best bit of the power curve, or ectended to acceptable..

i think 5 fps is np in 12fp guns. 2 or 1 is steyer turf, very acceptable.

 

fill to les than full mark, fill after the usuable shots... saves a bitta air every time, and stops you having those all over the shop shots... fill to much the consistancy goes every where and the power drops off silly untill it gets to the 200 bar or whatever, same when it's too empty.. power drops (at both ends). so get the sweet spot and fill to that.

Edited April 3, 2009 by ghillies