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PostPosted: Fri Feb 02, 2018 12:31 pm 
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Location: Ontario, Canada
Has anyone here experimented with testing the NP velocity in various temperatures. I recently acquired a .177cal Crosman Fury NP that needed some attention. I lightly polished the compression tube, piston and bore. Installed new piston seal. All turned out well. Burnished moly paste into the tube and also lubricated piston with moly paste. The rifle clocks smoothly like a dream and accuracy is acceptable for the price. It's averaging 5/8" ctc for 5 shots at 20 yards. This average is over 20 groups rather than a one-off group.

This Fury loses velocity in the cold. Yesterday it was at least -15C outside and I left the Fury in my vehicle for an hour or more. When I took it indoors I left it in the case for 15 minutes and then clocked the speed at only 805fps average with CPHP. After a couple of hours it climbed to 855fps and then 875fps after a little longer. This morning it's up to 880fps. I have had this rifle shooting as high as 930fps when my basement is quite warm but I'm not sure it will go this high again. I'm not sure if the problem is the moly paste getting thick or the NP being affected by the cold. Any other experiences?


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PostPosted: Fri Feb 02, 2018 12:56 pm 
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Actually I noticed the cold temperature affects everything...

On your Fury, it's about 10% dropped. I don't have my chrony yet. But obviously every air guns I once left in the car and found it shoots with lower fps afterwards until it's warmed up again indoors. That includes the CO2 pellet guns, the pumper (1322), the P17 etc...

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PostPosted: Fri Feb 02, 2018 1:59 pm 
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All but some synthetics thicken and slow movement in the cold There is no way around it. It happens. CO2 guns much more than springers and PCP's likely less than any others as there are

no critical moving parts upon firing, however, compressed air will lose pressure in the cold and become more dense. Nitrogen also loses pressure in the cold, according to the chart that Praxair gave me.

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PostPosted: Fri Feb 02, 2018 2:31 pm 
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interesting topic.

My understanding, everything loses volume as it gets colder. Water being a special case during crystallization. An unregulated pcp charged in warm conditions and allowed to cool should be affected somewhat more than their regulated counterpart. Anything charged in the same temperature conditions should experience less of the effect. I'm not sure of the affect on the actual ag itself as parts get colder they shrink too. Pellet as well. Cold vs warm pellets.

Worth some chrony testing. Maybe I'll take some of the quiet springers out in the garage tonight and see.

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PostPosted: Sun Feb 04, 2018 12:08 pm 
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I see a 40 fps drop with the gas rams when I shoot in the winter months over the summer ......whether its the type of lube or the NP itself I don't know but drop it does......

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PostPosted: Sun Feb 04, 2018 12:42 pm 
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Grease really gets stiff in freezing temps, even in just cold temps. A lot of oils do as well,

to the point of slowing down a bolt actioned CF rifle, to the point of miss fires. With an air

gun, you may also lose 'some' pressure, from not having a proper sealing piston.

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PostPosted: Sun Feb 04, 2018 5:24 pm 
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Seals also shrink in the cold. This may adversely affect piston seal efficiency, and reduce output pressure to the pellet. Or not to allow pressure to build, as I've found with a "cold" P17...

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PostPosted: Sun Feb 04, 2018 11:51 pm 
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I checked velocity again today and was getting 920 with the CPHPs. The rifle has been indoors for a couple of days.
The seal is new but could be shrinking in the cold. The lube likely thickens up in the cold. Maybe the NP is slower moving in the cold. Thankfully rifle seems to always return to better performance once warmed up. I wonder if it will speed up even more on hot summer days.


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PostPosted: Mon Feb 05, 2018 6:31 am 
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Just curious, does the poi change? Granted, over a longer range, the impact point will change. But at 10-20 meters can you still hit what you aim at, or is the poi way off until it warms up?

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PostPosted: Mon Feb 05, 2018 11:35 pm 
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ricksplace wrote:
Just curious, does the poi change? Granted, over a longer range, the impact point will change. But at 10-20 meters can you still hit what you aim at, or is the poi way off until it warms up?


I didn't want to shoot the rifle when velocity was down 100fps. The rifle is sweet to shoot so I didn't want to risk the strut leaking down. I tested maybe 10 shots when cold. I'm guessing that the 100fps might drop POI a little bit at 10 metres. Maybe a couple of pellet widths.

The NP1 has definitely been impressive, even with the temp sensitivity. It feels slick like a tuned springer when cocking. No twang, no vibration, quiet, easy cocking effort, snappy feel to the shot and decent accuracy. It shoots accurately from both a rest and offhand. The temp sensitivity is interesting and challenging to figure out why. The life of the strut will also be interesting to find out. I hope it lasts at least10,000 shots.

Not long ago I would never consider a nitro piston and was frustrated at the tendency of Crosman using them in so many models. I still like the metal springs for tuning options but the struts have now become another acceptable choice for me.


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