TEMPERATURE EFFECT ON FPS.

Forums PCP Airguns TEMPERATURE EFFECT ON FPS.

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    BWhunter67
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    I have had my .25 Marauder for a while now and finally got a Chrony to test it!! but it left me a little confused…The extreme spread over 32 shots was 26 with a standard deviation of 8.47. But what has me confused is the average FPS was only 734. The factory specs say 900 and i know that is usually higher than actual, but 170 fps seems like a big difference. My gun is completely stock with no modifications or adjustments. It was 25 degrees outside the day i tested it. I was wondering if anybody has tested their air rifle in the cold and if so what wat the FPS drop versus warm weather?
     

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    spysir
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     The temp would have a rather small effect on fps, to much or the wrong lube would be hit by temp the most, if your at the factory settings that’s just the fps you have unless you start making adjustments. As you ES is very good for a stock rifle maybe just leave it and shoot it, or, do try to keep track of where it is now set.   You didn’t say what pellet you are using, you can be sure the factory used something light to get the spec. numbers but with SO many adjustments on a marauder you can pretty well dial in the numbers you want – with shot count suffering as you go up in power-.
     Most people shooting the .25 only get 2 clips before needing to refill, yours will adjust theer if that is what you want.

    John

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    JDShapp
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    On factory settings mine shoots around 840fps on the best part of its curve. Usually I fill to 2800psi and refill at around 1800psi to get the 2 clips I expect out of a stock .25 marauder.

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    BWhunter67
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    Thanks for the info… I’m shooting the jsb heavy 33.9 grain. I was very surprised by with the ES too. Everything i read says 16 shots is about normal on the factory tune. I think i will record the factory settings and try tuning it for more fps. I’m not sure how much i want to adjust because the gun shoots great and is a tach driver in the current configuration. I would was just surprised by the low FPS. from what i read it seems like everybody is between 800-850fps. 

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    JDShapp
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    Should have mentioned that the 840fps was with 25.4gr JSB pellets so 734fps sounds about right to me for the 33.9gr ones.

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    spysir
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    Ya the 33.9g is very heavy ( but fine to use if they group well and your accustomed to them ) for a 40fpe rifle. Try the JSB and maybe even the “Benjamin” pellets they both often work well and you’ll certainly gain some fps.

    John

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    Bwalton
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    going from The Kings to the Heavies the loss is 90-100fps If I want to shoot the MKII then I have to turn up the power to shoot them at 935fps which is the best speed for my BT65, the only problem with that is when I put the Kings in,  it sends them well over 1000fps, so I decided to just put a reg in and shoot the Kings at 933fps where it has the best accuracy.

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