What is the difference between PCP and HPA?

[fisherdude]

I am new to this forum,  I have been thinking about a CO2, HPA or PCP rifle to add to my stable.  Could someone explain the difference between HPA and PCP.  It all looks like a compressed air tank on a rifle to me.

[Curioguy]

I’m glad you brought that up Ron.  I may have been around a little longer but never asked that question.  I’m familiar with C02 (have 3 of them) but don’t know the difference between PCP, HPA or CPA.  I’m sure someone will chime in.

[SDale]

PCP & HPA are close to the same thing.

PCP Meaning "Pre-Charged Pneumaic" . PCP guns are Unregulated. The only regulation of pressure being the valve and hammer.

HPA "High Pressure Air" . HPA air sources are regulated. Most of the time the tanks are 3000-3500 psi or more and output pressure is regulated anywhere from 700-1500 psi as it leaves the bottle.

PCP Gives a handful of good High Power shots. Velocities start low, then get high and rapidly drop off in a bell curve. whereas HPA gives allot more good CONSISTENT shots at a slightly lower velocity. Shots start at a given velocity and stay that way until the bottle pressure drops close to the regulated pressure. Shot count is dependent on cylinder volume. The bigger the tank, the more shots you get.

[ribbonstone]

..who were having trouble getting electronic guns to run on co2 and has problems maintaning vel. in winter months.  they made the move to HPA...as outlined, a high compression bottle (usually 3K-3.5K) with a regulator that only releases co2 type pressures (although some are running a lot lower than that now).

So HPA tanks are compressed to the same level as PCP's, but only that high pressure is seen by the bottle...the regulator only squirts out air at some pre-set lower pressure.  Becasue of that regulatore, the valve only sees pressure at the same level from shot to shot.

the two most common sizes used on airguns are 13CI and 22CI (which are "baby bottles" by paintball standards).  COULD use a larger (48CI) bottle on something like a Talon that uses the air bottle as a butt stock, but most people find them kind of "fat".

[3n00n]

The Angel internal reg is set at about 650psi, while the Ion is set at about 140psi - but the mechanismsare quite different from"poppet valve" designs.

[fisherdude]

Thanks for the information folks.  Now, I am considering getting a QB79 and converting it to HPA which seems like a dooable project for me.  However I have one last question.  How do I fill the tank?  Is there a pump I can get? I live in rural Arkansas, and I don't think there is a dive shop nearby.

[goodgroup]

I fill my Qb 79 's with 13 and 22 ci tanks using an FX superstroke pump.
I bought it used on the classifieds. I think they are $270 ish new.
It will keep you fit. Not so bad once you get in  pumping shape but it's a bit of a workout

With my setup I can easily unscrew the tank and take in to a dive shop because I have a high riser breech.
Since I got the pump I leave the tanks on the guns. A standard QB79 will not allow you to do this with an HPa tank
without removing the barrel or the tank block.

Jay

[ribbonstone]

Can get a look from this picture.  For me the easiest way to fit the HPA tank is to remove the barrel.  To do taht, will need to loosen the barrel band  and remove the barrel locking screw on the top of the breech, then slide the barrel off to the front.

Screw the HPA tank into place on the now barreless rifle.  4 out of 5 times, it will screw on tight and everything is in place for the barrel to go back on with no problem...about 1 in 5 guns end up with either the HPA tank nipple of the HPA tank gauge sticking up right where the barrel needs to be.  For those, will use a thin washer (do not let it cover up the co2 passage in the gas block) in the gas block so it stops rotation a fraction of a turn earlier.

In this picture are 3 HPA conversions.  Am using a brass gauged on/off, but the same system as above applies.  Notice they don't all line up exactly the same...the short one needed a thin washer/shim.


You do not need the on/off, can just screw the tank directly to the gas block.  Will leave the tank in place and just refill it by way of the fill nipple.


Do need a way to generate high pressure air, and for these a hand pump works just fine.  the pumps are going to cost between $200 (Discovery is currently the lowest price) and about 300 (Hill seems the higher priced unit).  Have used both the FX and the Hill.  

Figure on stopping shooting BEFORE the tank pressure reaches regulator pressure.  On my 850PSI tanks, will stop shooting at 1000PSI.  To get the tank filled from 1000psi to 3000psi takes about 120 pump stokes.  Usually do 40-50 strokes, then a good 10min. cool down before going back for another 40-50 strokes.  Figure on 3o-40min. to fill the tank.

[BigCat1]

Ribbonstone, do you see any difference in using the 78 tube compared to the 79 tube...................Troy

[ribbonstone]

IF nothing else, it gives your left hand (for a right handed shooter) something to grab besides the tank when shooting away from the bench.

Can't find any definate performance difference, but have a belief that I want to test.  Believe there is a lag time for the tank reg. to open and resupply air, so the shot really only uses the air trapped between the valve and the regulator. That's enough air at 850PSI for either of them to run the same when tuned to give 13-14foot pounds. the 20cal will give two good shots with the on/off turned to 'off'...the 79 will give one shot at the same power level.  So unless the tank regulator can supply air "right now", doubt I could get the QB mush past 15 foot pounds on 850PSI.

 Can get the long .25cal. QB up to 25.5 foot pounds, but doubt I could get a QB79 to run that fast...the long tube on the 78 is empty after one shot, there just wouldn't be enough air on tap to let that happen with a 79 at 850PSI.

So I have to do some tests in the next weeks. to see if that belief is correct.

My thought is that with the small volume available on the 79, if you wanted to get energy figures in the 20's, would need to run at higher than 850PSI.  To get that kind of energy with a longer tube, can do it at 850PSI.