bone stock 2240 except trigger mod. Temp in the Garage was 90 degrees. 100 plus outside. First shot with 14g pellets was 470fps. slowly crept up to a high of 479fps. Shot #23 first time velocity dropped below 400 down to 395. at shot #28 the velocity dropped below 300 to 295fps. .Question is: If it's shooting a little hot because of temperature is that going to give fewer shots at the top of the velocity?
2240 First Chronograph string and question for CO2 Gurus!
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"Question is: If it's shooting a little hot because of temperature is that going to give fewer shots at the top of the velocity?"
Maybe, but not necessarily. I've come to believe it's just not that simple, and relates to other inter-relating firing dynamics including the balance between the valve-spring and hammer-spring, hammer-bounce/valve-flutter, individual gun efficiency ("gas mileage"), and yes, temperature.
If you were shooting shot after shot without giving a little time between shots for several shots in a row, especially after 8-10 shots, you can probably achieve a much more impressive shot string by slowing your shooting cadence (considerably) once velocity starts falling.
I'd think you could get at least 20 very consistent (velocity) shots with a slow shooting cadence, then slow the drop in velocity after that by letting the gun warm for a minute or two between shots as Co2 depletes.
Maybe, but not necessarily. I've come to believe it's just not that simple, and relates to other inter-relating firing dynamics including the balance between the valve-spring and hammer-spring, hammer-bounce/valve-flutter, individual gun efficiency ("gas mileage"), and yes, temperature.
If you were shooting shot after shot without giving a little time between shots for several shots in a row, especially after 8-10 shots, you can probably achieve a much more impressive shot string by slowing your shooting cadence (considerably) once velocity starts falling.
I'd think you could get at least 20 very consistent (velocity) shots with a slow shooting cadence, then slow the drop in velocity after that by letting the gun warm for a minute or two between shots as Co2 depletes.
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I only plan on shooting the 2240 in the garage on paper once it is broken in. I did shoot 15 shots then let the gun sit for 10 minutes before shooting again, tried to pause some between each shot. Would a power adjuster tuned to slower fps give a worthwhile shot count increase? After 28 shots the fps dropped off a cliff down to barely slow enough to leave the barrel.
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Ron - it sounds like he was getting a decent shot string, just higher on the fps side than expected.
I'm not a CO2 expert, but I've learned about cool-down and gasification quite a lot from the airsoft world.
I would answer a most likely yes for the higher temp causing the higher fps. CO2, propane, butane, etc will be at a higher pressure at higher temperatures. At room temp CO2 is ~800 psi, in 90-100 degrees you could be pushing 900-1000 psi. This would give you more powerful shots, with the exceptions noted by Ron that higher pressure could also lead to valve lock, needing a strong hammer spring, etc. But maybe it wasn't high enough to cause that effect in this case.
The other thing Ron refers to is gasification. The conversion of the CO2 from a liquid state to a gas state. This process takes energy which you feel in the form of heat being removed from the CO2 cart and surrounding area (ie: the CO2 cart gets colder). Once the CO2 cart is cold the gasification process slows down and the gas sits at a lower pressure. If you repeat this process quickly your fps will go down because there is not enough energy to drive the gasification process (one of the reasons I hate semi-auto CO2 guns).
Hope this helps a bit.
I'm not a CO2 expert, but I've learned about cool-down and gasification quite a lot from the airsoft world.
I would answer a most likely yes for the higher temp causing the higher fps. CO2, propane, butane, etc will be at a higher pressure at higher temperatures. At room temp CO2 is ~800 psi, in 90-100 degrees you could be pushing 900-1000 psi. This would give you more powerful shots, with the exceptions noted by Ron that higher pressure could also lead to valve lock, needing a strong hammer spring, etc. But maybe it wasn't high enough to cause that effect in this case.
The other thing Ron refers to is gasification. The conversion of the CO2 from a liquid state to a gas state. This process takes energy which you feel in the form of heat being removed from the CO2 cart and surrounding area (ie: the CO2 cart gets colder). Once the CO2 cart is cold the gasification process slows down and the gas sits at a lower pressure. If you repeat this process quickly your fps will go down because there is not enough energy to drive the gasification process (one of the reasons I hate semi-auto CO2 guns).
Hope this helps a bit.
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I just ordered a lighter hammer spring hoping for more shots on one cart. If I get valve lock I will just have to be happy with 25 shots when the temperature is 90 plus in the garage.
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Yes, reducing power output will increase shot count... in EXPONENTIAL numbers to the amount of power decrease(s). In some cases, to amazing degrees. One excellent example as taken form Airgun Chronicles-
9mm Crosman Custom Co2 single-shot, 10” barrel
65gr .350 Speer ball, 80F., full power, 10 shot powerband- Low= 333, Hi= 353, ES= 20, SD=3, Average= 346 FPS/17.3 FP
65gr .350 ball, 80F,, reduced power, 23 shot powerband- Low= 293, Hi= 328, SD= 35, SD= 7, Average= 319 FPS/14.7 FP
Reducing velocity by 10% and energy by 15% improved shot count by 130%... a very good trade!
This 9mm custom is based on a Crosman 2250 and has an after-market power-adjusting screw.
CTS, You're about right on Co2 pressure at room temperature, but way low at 90-100 degrees. More like 1200-1500 PSI. Such drastic changes in pressure with temperature equal substantial changes in velocity. Here's an example of that (again from Airgun Chronicles)-
.22 Crosman 150 #8 Co2 single-shot, one-piece (bull) barrel model
14.3gr Crosman Premier, 68F., 10 shot string- Low= 402, Hi= 420, ES=18, SD= 5, Average= 413 FPS/5.4 FP
14.3gr Crosman Premier, 95F., 8 shot string- Low= 458, Hi= 466, ES= 8, SD= 3, Average= 462 FPS/6.8 FP
9mm Crosman Custom Co2 single-shot, 10” barrel
65gr .350 Speer ball, 80F., full power, 10 shot powerband- Low= 333, Hi= 353, ES= 20, SD=3, Average= 346 FPS/17.3 FP
65gr .350 ball, 80F,, reduced power, 23 shot powerband- Low= 293, Hi= 328, SD= 35, SD= 7, Average= 319 FPS/14.7 FP
Reducing velocity by 10% and energy by 15% improved shot count by 130%... a very good trade!
This 9mm custom is based on a Crosman 2250 and has an after-market power-adjusting screw.
CTS, You're about right on Co2 pressure at room temperature, but way low at 90-100 degrees. More like 1200-1500 PSI. Such drastic changes in pressure with temperature equal substantial changes in velocity. Here's an example of that (again from Airgun Chronicles)-
.22 Crosman 150 #8 Co2 single-shot, one-piece (bull) barrel model
14.3gr Crosman Premier, 68F., 10 shot string- Low= 402, Hi= 420, ES=18, SD= 5, Average= 413 FPS/5.4 FP
14.3gr Crosman Premier, 95F., 8 shot string- Low= 458, Hi= 466, ES= 8, SD= 3, Average= 462 FPS/6.8 FP
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Taking long pauses in between shots like 20-30 seconds between shots (longer the better) and allowing the gun to warm up alone will give you more shots. Do you have a very hot (ALL ELECTRIC) pad or body or foot warmer you can rest the gun on in between shots or Maybe even electric hot gloves? Hot blowdryer? Use Them keep that gun warm to hot and you will get best results and MORE POWER and MORE SHOTS TOO.
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Thanks Yo
Don't need more power but would enjoy a few more shots. I will post when I get the lighter hammer spring. Going to be hot weather here until September. Hard to pause between shots when you are having fun. I just had a thought. Have two or three guns set up to shoot. that would pause the CO2 gun.
Don't need more power but would enjoy a few more shots. I will post when I get the lighter hammer spring. Going to be hot weather here until September. Hard to pause between shots when you are having fun. I just had a thought. Have two or three guns set up to shoot. that would pause the CO2 gun.
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Get ready for a little Geek Salad.
Interesting to think about the questions raised here from the standpoint of the physics of gasification in CO2.
Higher ambient temperature means more energy is available for gasification of the CO2 molecules in the liquid state. Result:the rate of molecules leaving the liquid state for the gaseous state increases, leading me to think you'd get fewer shots as more liquid CO2 is consumed with each shot.
Then the converse occurred to me: each CO2 molecule moving into the gaseous state would be more energetic, accounting for the increase in pressure without the need for an increased rate of gasification of the CO2. In this case the number of shots is unaffected even as the power of each shot increases.
My guess is that both of these phenomena are occurring but I don't know what the proportion is of energy consumed by an increase in number of molecules releasing into the gaseous state versus the energy consumed in the increased motion of each gaseous molecule.
An interesting mind puzzle to ponder during the down time each day.
Interesting to think about the questions raised here from the standpoint of the physics of gasification in CO2.
Higher ambient temperature means more energy is available for gasification of the CO2 molecules in the liquid state. Result:the rate of molecules leaving the liquid state for the gaseous state increases, leading me to think you'd get fewer shots as more liquid CO2 is consumed with each shot.
Then the converse occurred to me: each CO2 molecule moving into the gaseous state would be more energetic, accounting for the increase in pressure without the need for an increased rate of gasification of the CO2. In this case the number of shots is unaffected even as the power of each shot increases.
My guess is that both of these phenomena are occurring but I don't know what the proportion is of energy consumed by an increase in number of molecules releasing into the gaseous state versus the energy consumed in the increased motion of each gaseous molecule.
An interesting mind puzzle to ponder during the down time each day.
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So we are learning that there are a lot of factors which can effect CO2 going from the liquid to gas state. I was doing a little reading to try and find out what CO2 pressures were at different temperatures and came across a plethora of information (about making beer).
Factors so far:
- external temperature
- barometric pressure
- amount of space for gasification (ie: free space in CO2 Cart and the plenum size in the valve.
Factors so far:
- external temperature
- barometric pressure
- amount of space for gasification (ie: free space in CO2 Cart and the plenum size in the valve.
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