Difference between CO2 and HPA

[BigTinBoat]

After reading a bunch of stuff here by rsterne and Ribbonstone, HPA has really peaked my interest and I wanted to see what the difference really was. I've heard that HPA "should be just a bit faster the CO2 at the same pressure".
I have an AS2250XT that was running off a 9oz CO2. I did some spring mods and got it running as efficient as I think I am going to get it. I am also pretty happy with the performance CPHP at 665fps, CPUM at 600 and Winny Domes at 620.
Well I searched and found a 17CI bottle as well as a Pure Energy reg for $40 total. Put them together and was kinda disappointed when I saw that the regulator was set at 600PSI. I have an on/off valve with gauge. (It was reading 850 in my basement with the CO2 at 70 deg so I think it is pretty accurate.)
Decided to shoot it was was surprised to see that I only lost an average of 20fps vs the CO2.

Well I went to a close paintball field and asked if they had any broken reg's. Guy at the field was nice enough to give me one. So now I have a stack of 10 Belleville washers and 2 shims.

Put one of the Belleville washers in and pumped the tank. Now reading 800 on the gauge, now just about equal to CO2.
I'm now getting 655 with the CPUM, 668 with the Winny Domes and 722 with the CPHP. I gained 15-20% in energy with just the HPA.

Now I just need to bleed the tank back down and put in another washer. I would really love to get to 700 with the Winny Domes w/o changing the spring. If I do this will be my go to plinker. Of course now the wife might say I have no reason to get either the S200 or the BSA Ultra I been eyeing up.

[rsterne]

700 psi HPA is roughly equivalent, in most guns, to CO2 at room temperature (850 psi)....

If you shim up the regulator too much, the spring/bellevilles will become coil bound, the pressure will go to whatever is in the tank (3000 psi), and you will blow the output side burst disc.... Best to have a spare pair of shorts handy....

Bob

[Ribbonstone]

Many of the modern paintball guns run at lower air pressure, in the 450-600[psi range.  So some of the bottles are set for that pressure, which really is too low for most airgun uses.  The same bottles can be had in the 800-850psi range, which works with some paintball markers just fine, and works with airgun conversions quite well in the 10-15 foot pound range.

850psi of air will move a pellet a bit faster than 850psi of co2, even if they both release the same volume of gas.  Air is just "thinner" than co2, so it flows better and generates a bit more speed/energy.

[BigTinBoat]

700 psi HPA is roughly equivalent, in most guns, to CO2 at room temperature (850 psi)....

If you shim up the regulator too much, the spring/bellevilles will become coil bound, the pressure will go to whatever is in the tank (3000 psi), and you will blow the output side burst disc.... Best to have a spare pair of shorts handy....

Bob

Actually it wasn't that bad. I put a 1.8K disk on the high side and then filled the little bottle from a bigger bottle that had 2K in it just to see what would happen. When it got to about 1600 it went. Maybe it was because I was ready for it. But it does give a good "pop".

Anyway I moved some washers around and got to the output gauge to 1000 even (the PE reg has silver washers which are a bit thicker then the black ones inside the reg he gave me so I have a good bit of adjusting I can do by switching or adding) and here are the numbers. I'm satisfied ( I think) so no changes to the hammer spring - plus not being at 12fpe I still have reason to keep looking at the S200 right?

1000psi
CPHP (7.9) - 765
Winny (9. - 710 - I guess the "8" and the ")" next to each other automatically gives you a smiley - kinda nice since this is my favorite pellet
CPUM (10.5) - 693
RWS (8.3) - 757

Looks like I am getting between 10 and 11 FPE depending on the pellet weight. Only shooting 10m indoor right now, but should be pretty flat outside at 40. Now I will not have to worry about the temp this winter, and  I can still shoot with the CO2 indoors w/o any other mod's.

rsterne and Ribbonstone -I can't thank you guys enough for the information you have provided on this forum.

Now I just need someone to get me an inner rod for my G4 pump. I'm using my Benji which is no where near as efficient. My G4 pump is not pumping right and it looks like I will need the valve at the end of the inner rod. I emailed Air Venturi and am awaiting reply. If I can't get the rod from them it looks like the benji rod is just a bit longer so I could likely get one of those and modify it to fit.

[BigTinBoat]

Many of the modern paintball guns run at lower air pressure, in the 450-600[psi range.

Yeah I think the reg I got was one of these lower ones. Can't complain though since I only have about $40 in the 17ci bottle and reg, and now it's at 1000psi.

[BigTinBoat]

Not wanting to leave "well enough" alone (Why can't we do that?) I decide to bump up the pressure. Took to bottle to 1200psi, but the velocity dropped. OK - hammer spring needs help. Put the full length stock spring in a here's what I get:

CPHP 7.9 from 765 up to 812
RWS 8.3 from 757 up to 806
Winny 9.8 from 710 up to 756
CPUM from 693 up to 735

I'm feelin pretty good - all FPE are up over 11 now and the 2 heavy pellets are 12.4 and 12.6

I notice that after a shot the gauge takes a second to recover back to 1200. Take the regulator apart and notice that the piston o-ring is separating. Guess what I don't have......a 013 ring. Oh well, satisfied with the performance, but now I have to wait for some new o-rings to arrive before I can shoot again...or maybe I'll just shoot up these CO2 bottles.

[BigK]

700 psi HPA is roughly equivalent, in most guns, to CO2 at room temperature (850 psi)....

If you shim up the regulator too much, the spring/bellevilles will become coil bound, the pressure will go to whatever is in the tank (3000 psi), and you will blow the output side burst disc.... Best to have a spare pair of shorts handy....

Bob

It depends on the valve volume, valve timing, barrel, and pellet weight.  For a CO2 gun set up for maximum power out of CO2, it will equate in terms of FPE to about 1100-1200 PSI on a similar gun optimized for the HPA.   

[rsterne]

HUH?.... Please explain....

Bob

[Ribbonstone]

With Bob on this.  Air is basically a "thinner" gas than co2, so it flows better at the same pressure.

The odd thing about this set up with a gauged on/off between the tank and the tube is that if you are careful, can work the on-off to fill thew tube to wahtever pressure UNDER regulated pressure you care to try.  Can get 400psi, 500psi, 600, psi, etc. by using the on/off carefully.



Basically, find that 700-750psi on air pretty well equals the performance of co2 at 800-850psi (pretty well "room temperature" co2).  Only takes something like 900-950PSI of air to equal 1100psi (warm weather co2).  Past that, co2 can't keep up.

[rsterne]

It's not just because CO2 is thicker (more viscous), it's heavier, so it takes more energy to accelerate that gas out the barrel.... You may not think CO2 weighs very much, but for CO2 at 850 psi, a .22 cal gun that shoots 14.3 gr pellets at 650 fps (13.4 FPE) from a 24" barrel would shoot 772 fps (18.9 FPE) if it didn't have to accelerate the CO2.... It takes 5.5 FPE of energy to accelerate the CO2 to 650 fps.... Air only weighs 2/3rds what CO2 does, so less energy will be lost accelerating it....

Bob

[BigTinBoat]

It depends on the valve volume, valve timing, barrel, and pellet weight.  For a CO2 gun set up for maximum power out of CO2, it will equate in terms of FPE to about 1100-1200 PSI on a similar gun optimized for the HPA.

My results show exactly the opposite. Air at 600 is just below the CO2 at 850. Air at 800 was giving me an additional (average) 50fps.
Air at 1200 is about 150fps more.
I'd have to agree that Bob's estimate of 700PSI Air being just about equal to CO2 (at about 73deg with the gauge reading 850psi)

[Ribbonstone]

Seems pretty easy to test.

1. Put on a co2 tank.  Note the pressure on the gun side.

2.Shoot 10 shots for an average.

3. Unscrew the co2 tank.

4. Bleed off co2 by leaving on/off to "on".

5. Turn the on/off to off.

6. Screw on a regulated HPA tank.

7. Slowly open the on off until the pressure in the gun equals co2 pressure, turn HPA tank to off.

8. Shoot one shot.

9. Crack open the 0n/off to let HPA tank to fill back up to co2 pressure, turn to HPA tank to off.

10. Shoot a shot.

11. Keep doing #7 to #9 until you get 10 shots to average.

[BigTinBoat]

Just thought I would update where I am with this conversion.

Shoots real nice with the CO2 as I got it up to just over 700 fps with RWS 7.0 WC's and up to 640 with the CPUM's. Lots of shots too (over 500 per 9oz bottle)

Winter is just around the corner though and I found a pretty good deal on a 17CI HPA bottle. Played around with the regulator and went as high as 1200PSI. Set there I was getting the following:
RWS 7.0 - 852 FPS
Gamo 7.8 - 815
CPHP 7.9 - 812
RWS 8.3 - 806
Winny Dome 9.8 - 756
CPUM 10.5 - 735

At this PSI is seemed to be using a bit more air then I had hoped (gauge seemed to be dropping pretty quick with every few shots) so since I have a 1720T on the way (that I will mod for my 12-15FPE hunting gun) I decided to run this one at 1000PSI which will give me between 10-11.5FPS (depending on pellet) for (I'm guesstimating here) probably 250+ shots.
Here is where it sits, and shooting real nice.
RWS 7.0 - 805 (10.1fpe)
JSB Exact 8.44 (By far it's favorite pellet) 758 (10.77fpe)
Winny Domes 9.8 (2nd favorite) 716 (11.16fpe)
CPUM 10.5 (least favorite) 700 (11.43fpe)

I have it sighted in with the JSB at 17yds. This gives me a 43yd "kill" range of .5". It's .5" low at 12y and 43y. It's .5" high from 25-30.

This will be my backyard plinker

[Ribbonstone]

Nice. Good to see the final product.

Think you're likely to get that 200-250 shots per fill with 17ci at that energy level.

[BigTinBoat]

Nice. Good to see the final product.

Think you're likely to get that 200-250 shots per fill with 17ci at that energy level.

When I was sighting it in with all the different pellets at 17yds I shot 40 pellets and it went from 2400 to just about 2100, so that's where my guesstimate came from.

[Ribbonstone]

Seems reasonable to me.  Worked at it, and the .177 was the lest cooperative, but got 180shots @ 12 foot pounds (in a QB), so figuring your 17ci tank is about 30% larger in volume, should give 30% more shots...or about  234.

[imadunatic]

Guys, sorry for ressurecting the post from the dead (and really the afterlife now, I know it's 2 years old), but most of the discussion I was hoping to have is in this thread with the exception of 1:

Is the shot count directly correlated to the size of the bottle?

I.E. As Ribbonstone said:

Seems reasonable to me.  Worked at it, and the .177 was the lest cooperative, but got 180shots @ 12 foot pounds (in a QB), so figuring your 17ci tank is about 30% larger in volume, should give 30% more shots...or about  234.

Using this logic, is it safe to assume that a 62 ci bench bottle will give me ~850 shots? Going to the extreme, is it safe to assume a 80 CF bench bottle will give me 1,902,832 shots (hence why I think there is an algorithm at play here, not a linear relationship between the two. I got to that number by 80cf = 138,240ci / 17ci = ~8131 x 234 = ~1,902,832)

I know men much smarter than I have probably figured this out and can poke holes in my logic, that's exactly what I'm looking for.

I'm on the verge of trying HPA in my QB, but I'd like to get a feel for shot count if I go the absolute cheapest way out to start without pumping just to get a feel for it (used 3000 PSI scuba is $50 (full) at my local dive shop, $30 adapter to fill 62 ci tank, 62 ci Ninja tank is $65 on Amazon which means I could test drive this setup for about $150. But if I'm only looking at 1000 shots off the scuba, I need to factor in several trips also).

Thanks in advance and sorry again for digging this up, it just seemed to make more sense responding to this rather than start a new discussion.

[BigTinBoat]

Guys, sorry for ressurecting the post from the dead (and really the afterlife now, I know it's 2 years old), but most of the discussion I was hoping to have is in this thread with the exception of 1:

Is the shot count directly correlated to the size of the bottle?

I.E. As Ribbonstone said:

Seems reasonable to me.  Worked at it, and the .177 was the lest cooperative, but got 180shots @ 12 foot pounds (in a QB), so figuring your 17ci tank is about 30% larger in volume, should give 30% more shots...or about  234.

Using this logic, is it safe to assume that a 62 ci bench bottle will give me ~850 shots? Going to the extreme, is it safe to assume a 80 CF bench bottle will give me 1,902,832 shots (hence why I think there is an algorithm at play here, not a linear relationship between the two. I got to that number by 80cf = 138,240ci / 17ci = ~8131 x 234 = ~1,902,832)

I know men much smarter than I have probably figured this out and can poke holes in my logic, that's exactly what I'm looking for.

I'm on the verge of trying HPA in my QB, but I'd like to get a feel for shot count if I go the absolute cheapest way out to start without pumping just to get a feel for it (used 3000 PSI scuba is $50 (full) at my local dive shop, $30 adapter to fill 62 ci tank, 62 ci Ninja tank is $65 on Amazon which means I could test drive this setup for about $150. But if I'm only looking at 1000 shots off the scuba, I need to factor in several trips also).

Thanks in advance and sorry again for digging this up, it just seemed to make more sense responding to this rather than start a new discussion.

Working backwards to figure this out I come up with about 5K-7500 shots on an 80cf bottle, assuming that you are getting the 234 shots from a 17ci bottle going from 3K down to a regulated pressure of 1K.

You are correct that the 62ci bottle would give 853 shots from 3K down to 1K. Since the 3K scuba bottle will not even fill the 62ci bottle to 3K a single time I used a 2K to 1K range. If the regulator is set at 1K and you are getting 853 shots from 3K then you would get about 426 from 2K to 1K. Using the sikes calculator an 80CF bottle filled to 3K will fill a 62ci bottle from 1K up to 2K 11.3 times. This would give you the first 4800 shots. The scuba bottle will now be at 2K. The scuba bottle will then fill the 62ci bottle from 1K to 1500psi another 11. times. This 500psi should give you 213 shots each fill for an additional 2385 shots. (7185 so far). Now your bottle will be at 1500 and you can change your fill pressure to 1300 and get another 7.4 fills. Using the same ratio you should be able to get 125 shots per fill for an additional 925 shots. You are now at 8110 shots total. Based on the fact that you will waste a small amount of air with each fill you not get quite this many shots.

[imadunatic]

Thanks BTB. Was trying to figure out how to back into that using Lloyd's calculator, but was at a loss. This gives me more to think about now.

Still glad you made the switch to HPA 2 years later? Or did you end up going back to CO2?

[BigTinBoat]

Thanks BTB. Was trying to figure out how to back into that using Lloyd's calculator, but was at a loss. This gives me more to think about now.

Still glad you made the switch to HPA 2 years later? Or did you end up going back to CO2?

No regrets at all. I've gone pretty much all HPA/PCP now. Only have a 2300 and a 1077(wife's) that run on 12g carts. I would like to get a blow back bb or pellet pistol with 12g carts just for gun.
Everything else is bottle fed HPA or PCP.