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 Post subject: 2240 velocity vs temp
PostPosted: Sat Mar 08, 2014 3:54 pm 
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Joined: Wed Feb 19, 2014 7:06 pm
Posts: 14
Location: Ottawa
I've read that temperature is a factor in the performance of CO2 guns but I couldn't find any posts with specifics on the effect of temperature and velocity with the 2240. I decided to try a little experiment to get some numbers and thought I'd share the results. It's not overly scientific but interesting none the less.

With a new CO2 cartirdge installed in a stock 2240 I took 5 shots with 14.3gr pellets through the chrony. Room temp was 19c.
Avg velocity was 413.6ft/s - 5.4lbs/ft - 7.4J

I put the pistol in the fridge which was at 4c. After an hour, took it out and took 5 shots.
Avg velocity was 346.7ft/s - 3.8lbs/ft - 5.2J

I then put the pistol in the freezer which was at -13c. After an hour, took it out and took 5 shots.
Avg velocity was 285.5ft/s - 2.6lbs/ft - 3.5J

I left the pistol out for an hour to let it return to room temp and took 5 more shots.
Avg velocity was 403.4ft/s - 5.2lbs/ft - 7.0J

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PostPosted: Sat Mar 08, 2014 4:00 pm 
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Joined: Thu Aug 02, 2007 7:54 pm
Posts: 356
Location: Quebec, Canada
Yeah i went to the range today and shot my qb and even though its a 580 fps (without the modded valve that i installed later and didn't retest it probably in the 600's now on Co2 and at 50 yards i was about 7 mil dots hold over and i could see the pellet in the scope. i found that weird since at the velocity its shooting i would of figured it would of been less hold over. but then i got my answer it was way to cold outside (-6) to get the co2 temp to shoot good.

then i decided to put it back in the case and shoot some .303 instead :) and also watched a guy shoot some .45-70 hornady rounds in his lever action.... Elephant killer i suppose! haha


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PostPosted: Sat Mar 08, 2014 5:44 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
You want to try an interesting experiment?.... Shoot ten shots as fast as you can (at room temp) measuring the velocity of each and watch it drop like a stone.... Then let it warm back up (it will be cold) for an hour, and shoot 10 more shots, but wait 2-3 minutes between shots.... BIG difference....

If you install a power adjuster and REDUCE the hammer spring preload while shooting a shot every 2 minutes at room temperature, you will find you can back off the preload quite a bit before the velocity drops.... If you set the preload so the velocity has JUST started to drop, you may nearly double your shot count.... Not only that, it makes the gun less sensitive to temperature changes....

Read this thread and it will explain it.... topic59801.html

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Mar 08, 2014 7:02 pm 
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Joined: Wed Feb 19, 2014 7:06 pm
Posts: 14
Location: Ottawa
Thanks Bob, that thread was a good read! Nice work! I may have to get one of those velocity adjusters. :D

Yeah, I've seen what happens to the velocities when quickly shooting at room temp. Big ft/s swings. At room temp I've seen as much as 30-40ft/s over short strings.

Surprisingly, what I found when quickly shooting at 4c and -13c was a very low spread in velocities. At 4c there was only an 8ft/s extreme spread and at -13c only 6ft/s.

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