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Mr.C

PCP Servicing

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    So, in the summer when it was HOT, I got chronoed and it read 780fps @ about 30°. I chronoed yesterday and the 40 shot sweet spot averaged 749 @ 6°.

    So is this purely to be expected and down to temperature or do I need to get the gun serviced? 

    I've been using it for 18 months and it was serviced a year before I bought it and unused till I got it. I shoot an hft comp most Sundays.

    Ta

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    Pretty average to see energy fluctuations with temparature .happens with spring guns too .though they tend to often increase in velocity when cold .

    In a pcp you have a contained amount and pressure of air .when its released it expands rapidly into the surounding atmosphere  .the  density of the air around you will determine how fast your pressurised  air will expand. The bore of your barrel can get a touch tighter and your hammer and spring may not move as fast and open the firing valve as much when you fire. Its all normal .the air pressure can fluctuate day to day and cause differences in your gun. 

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    Witnessed the effect on poi of the pellet at long range when the outside air temperature changes due to just the sun coming out.  Mate and i were shooting some excellent groups at 100 yds one cool morning .then the sun popped up and as the temp rose the poi shifted and dropped (this was not due to the air quantity in our guns ) group sizes also opened up .

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    Yep ,absolutely spot on from Ultrastu,temp variation also has a surprising effect on shot count in P.C.P.s.

    One of the main reasons i check the  zero before hunting at night .

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    Contained gases pressure  increases with heat.
    Put 30 lbs in a tyre on a cold day, you will find it goes up 2-3 lbs on a hot day , or after driving.
    PCP tanks are no different.
    The peculiarity of physics means when you fill that tank from say, 100 bar to 200 bar, it increases in heat temporarily , feel  the metal next time you do it.
    Like wise continuous gas release cools it.

    This is why you see ice forming on propane cylinders during use sometimes.
    Also note a rapid pressure drop from 12gram Co2 cylinders if you rapidly fire a Co2 pistol, when the temperature returns to ambient, the pressure returns.

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    Yup makes sense and explains why I've been dropping out of 45yrd kills (HFT) and splitting short 15mm's. Or it could just be me !

    Thanks for your replies.

    Edited by Mr.C

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    42 minutes ago, Mr.C said:

    Yup makes sense and explains why I've been dropping out of 45yrd kills (HFT) and splitting short 15mm's. Or it could just be me !

    Thanks for your replies.

    No its not you.

    Lower tank or reg pressures can shift POI , depends on tank size to an extent.

    One factor that often came up in FT during the winter months was shift in POI due to scope temperature, so many participants had a hot dial, and a cold dial.
    It was usually a matter of 2 - 4 clicks , but on the longer targets it could be enough to miss.
    Some scope makes tended to be more prone to it than others, the big Nikkos being particularly bad for it , whilst my Falcon didnt seem to suffer ?
    Its why you sometimes see them with a strip thermometer on the side of the scope.

    I know you dont dial in HFT , but a general rule of thumb , a longer shot needs that little bit more of a higher range estimation in winter.

    Edited by Rewulf

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    I have a Viper Connect so my face is pressed up against the end, zero eye relief. Cheers for the pointers

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    No it has no reg, but shot 1 was 760 and the next 40 were all between 748 and 754 and then it started falling off. I went on as far as shot 80 but was down to about 9ftlbs by then.

    You're prob right, but I like to blame the wind. ...............

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    11 minutes ago, Mr.C said:

    shot 1 was 760 and the next 40 were all between 748 and 754

    For a non regged gun thats pretty good !

    An MPR has an AA 400 size cyl does it not ,? 80 shots is asking a bit much for consistency !

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    Yes it does. 

    Was going to run a complete cycle full to empty. Usually shoot a zero check on the plink plus 30. Occasionally 50 so wondered what was possible. 

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    Ok .so what gun is it ? 

    Some guns energy tends to increase from new with use . (Bsa ,hw ,pcps .) 

    Some decrease  .daystate  are known to do this a lot. 

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    Bruno was right it's an MPR FT completely stock apart from some extra spacers to increase lop. And Ive taken the cosmetic air stripper off. 

    Still wondering how often they need servicing. 

     

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    19 hours ago, Mr.C said:

    Bruno was right it's an MPR FT completely stock apart from some extra spacers to increase lop. And Ive taken the cosmetic air stripper off. 

    Still wondering how often they need servicing. 

     

    If its still performing then i doubt you need a service.

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    9 minutes ago, Mice! said:

    If its still performing then i doubt you need a service.

    +1 

    Be interesting to know what they actually do on a service ?
    I can get my car done cheaper 😃

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    The main thing involved in a service is replacement of o rings . (There are loads of them in a pcp stopping the air escaping ) they get brittle and crack after a few years. Some guns are worse than others and there are different grades of oring .

    Id say most guns dont need an oring change within 5 years .

    Most my bsa ultras are still on origional rings at 10 years old now. 

     

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