Psi/bar, and what pressure to charge my PCP rifles to?

[JimD]

Fill pressure on an unregulated gun is a function of the tune. With the stock tune I filled my Prod to 2500 because that was only slightly higher than were it got peak velocity. You could just fill to the peak but the shot string would be shorter than filling slightly higher if you measure your shot string as the number of shots at a given velocity variation. I increased my transfer port size and found I could utilize the full 3,000 pressure but only with 7 turns in on the hammer spring. That got me nearly 20 ft lbs but also only about 10 shots. So I currently shoot it at 700 to 750 fps with 14.3 or 14.66 grain pellets for 17-18 ft lbs. I get about 20 shots at pretty stable velocity. My fill pressure is 2700.

My process to decide fill pressure is to shoot a shot string while measuring the velocity (I use a cheap chinese chronograph after shooting my old chronograph, about $35 off Amazon) and then look at what will give you a nice shot curve for what you want to do. Once you have the data it doesn't take long to analyze. I look for a maximum spread of around 40 fps - 20 up and down from the average. Some guns may do better than this for a nice long shot string.

With the Avenger I shoot targets as I measure the velocity (the Prod doesn't like this, the Avenger doesn't care much - the chinese chrono clamps to the shroud). I am looking at the velocity at the regulator setting and then increasing hammer spring tension to see what happens to both velocity and accuracy. It is also possible to vary transfer port size and barrel port size on some guns. Increasing the port diameter increases velocity.

 

[Emu]

PCP's pieces under pressure are a combination of:

a) Metal;

b) Rubber o'rings;

c) Bottles normally are composite or also metal.

If you do not make something irresponsible, the advertised pressure will not damage the metal/composite parts.

O'rings will eventually fail and will need to be replaced, by yourself or by another person.

The more pressure you put on your rifle, the less the o'rings will last, but even with pressure under the specifications the o'rings will not last forever.

A cheap air rifle will economically have cheap quality and more possibility of having a lesser lasting.

A good quality rifle (Airgun Technology - Vulcan and Uragan-, Daystate, FX and some Korean airguns as Evanix and JKHan) with appropriate maintenance, will last forever and will give you joy.

Bad quality air rifles will make you waste your money in shooting pellet after pellet trying to make that bad rifle to shoot well.

How much you want to suffer with the PCP's you buy vs. how much money you think you save buying a cheap rifle, is your own decision.

Normally, the cheaper the rifle is, the bigger the desperation it causes.

Your choice.

 

[Tomygun1]

So thank you all for your input as I truly seek knowledge and have learned much here about pressure. Thanks to GeneT I better understand bar/psi, and like him I still resist bar as I completely understand psi and find its measurement to be finer. Special thanks to JamesD as he has already done the testing I plan to do with the Avenger and apparently successfully. Thanks Airmanator, and the reason I compare the Avenger to the Cayden is specific to my question, they are so different. Let me tell you of a big blunder I made when I by accident filled my non regulated Stormrider.177 to 4100psi. It functioned the best ever, was accurate, and for the first time loved slugs, and completely penatrated a fir 2X4. Too bad I can’t safely duplicate that. I nave since made a chart for my PCP’s and taped it to the compressor. JimD, DesertSilver, Fatmike, Odoyle and others I thank you all for your experience and educating me where I was lacking, I may be an old guy but am a fast learner.

I just received an order from China today from Discovery Scopes and hope to give a review soon. But first off I can say that their new offering for a rimfire high brilliance fully multicoated lenses VT-R 4X16X44mm/30mm tube side focus was bucks well spent. Included were flip up caps, sun shield, rings, and side focus wheel for $82. Only problem is that like all the others it won’t center on my Cayden or Avenger. I sent off a complaint to Crossman with a request for replacement rails but know it’s time to set up my milling machine and do what the factory should have done in the first place. Just FYI..

Tom