Redux data: HPA to CO2 velocity shift

CJOttawa · 04-26-2011, 03:24 PM

I tested Redux 043 yesterday on both 12-gram CO2 and HPA via remote and wanted to post results.

This is meant as a general guideline to give users an idea of what to expect when making a switch between constant air with an HPA source and 12-gram CO2.

Test conditions:

approx. 16°C/61°F, overcast sky
13ci, 3,000 PSI HPA tank with a Smart Parts MaxFlo SIS tank regulator
Marballizer paint, approx. 0.678 caliber
TyMcneer 0.675 brass insert
extended Redux barrel (approx. 7.25 inches)
ASP open face bolt
#6 power tube
red main spring, blue valve spring
milled hammer, approx. 29-grams with sear (versus 43 grams unmilled, stock CCI hammer)

I observed a velocity shift of 15fps, making no changes other than substituting HPA for CO2, with CO2 having the higher velocity. (~285fps on CO2, ~270fps on HPA)

HPA tanks typically output at 800psi and CO2 is ~850psi at room temperature which is a component of the velocity change, along with valve configuration.

All this to say, if you're making a switch between HPA and CO2 and have a Redux configured similarly to my own as many are, expect about a 15fps velocity change.

DSA · 04-26-2011, 07:11 PM

Great stuff Cj, what size if tank did you use and do you happen to have a total shot count? Im thinking DDay here.

CJOttawa · 04-26-2011, 08:12 PM

Quote:

Originally Posted by DSA

Great stuff Cj, what size if tank did you use and do you happen to have a total shot count? Im thinking DDay here.

13/3k!

No shot count as I didn't empty the tank but 1,000psi gave me 40+ shots, possibly a lot more.

Figure 100+ shots from a 13/3k tank but a well tuned pump might net you 200+ shots.

short304 · 04-27-2011, 02:57 PM

Awesome info CJ! thanks!

Altec · 04-27-2011, 03:24 PM

That is very interesting. On my Sheridan's I always observed a more severe drop in velocity. Roughly a 35FPS drop. Since I ran my markers at 275FPS, I would always get about 240FPS with HPA. Didn't notice much difference between my 850PSI output tank, or my 900PSI output tank either.

How was the difference in report?

CJOttawa · 04-27-2011, 04:02 PM

CO2 produced a bit more quiet shot than HPA.

I wouldn't be surprised if the velocity change I observed was on the low end of possible; it was cool out (less than 65F) so the CO2 wasn't at as high a pressure as it would be at 70 or 80F.

See this graph of CO2 pressure versus temperature.

tymcneer · 04-27-2011, 04:10 PM

What is really needed is to see what the differences are, when the output of both the CO2 and the HPA are exactly the same. That would allow us to determine the difference in the gas' "efficency" in pushing a paintball. Then a formula could be determined to allow someone to understand what must be done to change from CO2 to HPA and back without the massive changes in velocity.

Ty

CJOttawa · 04-27-2011, 05:10 PM

Quote:

Originally Posted by tymcneer

What is really needed is to see what the differences are, when the output of both the CO2 and the HPA are exactly the same. That would allow us to determine the difference in the gas' "efficency" in pushing a paintball. Then a formula could be determined to allow someone to understand what must be done to change from CO2 to HPA and back without the massive changes in velocity.

Ty

I'd be game having the HPA tank regulator tweaked to output 850psi. (replacing or shimming the spring perhaps)

chopper duke · 04-27-2011, 05:20 PM

Quote:

Originally Posted by tymcneer

What is really needed is to see what the differences are, when the output of both the CO2 and the HPA are exactly the same. That would allow us to determine the difference in the gas' "efficency" in pushing a paintball. Then a formula could be determined to allow someone to understand what must be done to change from CO2 to HPA and back without the massive changes in velocity.

Ty

What if something like a Maxflo was used and the output was set at 850/900 for both?

the_chemist · 04-27-2011, 05:22 PM

You would run them both through an HP reg, you will usually find CO2 to produce a higher speed at the same pressure with different valves having higher differences.

This is because CO2 has a low compressibility factor(iirc ~0.4 compared to 1.1 for HPA at 1000psi). Meaning it is denser at high pressure and as the pressure goes down it expands faster. It doesn't necessarily mean it is more efficient by weight(it isn't) but combined with condensation it is obviously more efficient by space. The sound thing is related to the speed of sound in different gasses

04-26-2011, 03:24 PM	#1 (permalink)
CJOttawa Immune to sales tactics. Join Date: Dec 2006 Location: Canada's National Capital	Redux data: HPA to CO2 velocity shift I tested Redux 043 yesterday on both 12-gram CO2 and HPA via remote and wanted to post results. This is meant as a general guideline to give users an idea of what to expect when making a switch between constant air with an HPA source and 12-gram CO2. Test conditions: approx. 16°C/61°F, overcast sky 13ci, 3,000 PSI HPA tank with a Smart Parts MaxFlo SIS tank regulator Marballizer paint, approx. 0.678 caliber TyMcneer 0.675 brass insert extended Redux barrel (approx. 7.25 inches) ASP open face bolt #6 power tube red main spring, blue valve spring milled hammer, approx. 29-grams with sear (versus 43 grams unmilled, stock CCI hammer) I observed a velocity shift of 15fps, making no changes other than substituting HPA for CO2, with CO2 having the higher velocity. (~285fps on CO2, ~270fps on HPA) HPA tanks typically output at 800psi and CO2 is ~850psi at room temperature which is a component of the velocity change, along with valve configuration. All this to say, if you're making a switch between HPA and CO2 and have a Redux configured similarly to my own as many are, expect about a 15fps velocity change. Last edited by CJOttawa; 04-27-2011 at 04:15 PM.

04-27-2011, 03:24 PM	#5 (permalink)
Altec Alternator Customs Join Date: Oct 2006 Location: SoCo, Maryland	That is very interesting. On my Sheridan's I always observed a more severe drop in velocity. Roughly a 35FPS drop. Since I ran my markers at 275FPS, I would always get about 240FPS with HPA. Didn't notice much difference between my 850PSI output tank, or my 900PSI output tank either. How was the difference in report? __________________ Alternator Custom Shop Delrin Barrel Loudeners (Any Barrel Size!) Coming Soon- Sheridan "Insta-Pierce" assemblies (PM for Details) BEO Mafia

04-27-2011, 04:10 PM	#7 (permalink)
tymcneer Brass Monkey Customs Join Date: Oct 2006 Location: Baltimore MD	What is really needed is to see what the differences are, when the output of both the CO2 and the HPA are exactly the same. That would allow us to determine the difference in the gas' "efficency" in pushing a paintball. Then a formula could be determined to allow someone to understand what must be done to change from CO2 to HPA and back without the massive changes in velocity. Ty __________________ Brass Freak compatible and Equation inserts in .670, .675, .680 and .685 Still selling brass tubing, with .678 barrel stock now available! My feedback: MCB - eBay - AO

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04-27-2011, 04:02 PM	#6 (permalink)
CJOttawa Immune to sales tactics. Join Date: Dec 2006 Location: Canada's National Capital	CO2 produced a bit more quiet shot than HPA. I wouldn't be surprised if the velocity change I observed was on the low end of possible; it was cool out (less than 65F) so the CO2 wasn't at as high a pressure as it would be at 70 or 80F. See this graph of CO2 pressure versus temperature.

04-27-2011, 05:22 PM	#10 (permalink)
the_chemist Post Whore Join Date: Jan 2010 Location: San Fran now	You would run them both through an HP reg, you will usually find CO2 to produce a higher speed at the same pressure with different valves having higher differences. This is because CO2 has a low compressibility factor(iirc ~0.4 compared to 1.1 for HPA at 1000psi). Meaning it is denser at high pressure and as the pressure goes down it expands faster. It doesn't necessarily mean it is more efficient by weight(it isn't) but combined with condensation it is obviously more efficient by space. The sound thing is related to the speed of sound in different gasses