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Chrono CB-625 a litle confused

Discussion in 'Anything Airgun Related' started by D4V1D, Sep 27, 2009.

  1. D4V1D

    D4V1D Posting Addict

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    I was having doubts about my Air Arms 410 power. I brought myself a chrono cb625 and had to enter my pellet wieght into it in grains?:eek:. On the tin it states 0.547 Grams I think this = 8.4 grains :confused: I'm using Air Arms Diabolo Field.
    After a couple of shots I found out that My rilfe is shooting at 715 FPS & 9.55 PDS.
    Is 9.55 pds = to 9.5 Ft.Lbs ? or do I have to convert 715 into
    Ft.Lbs.

    Thanks for your help. :D
     
  2. Andy

    Andy Administrative Staff Member Founder

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    As long as you have entered the correct pellet weight, then pds is the same as ft/lbs.
     
  3. thelonesomepine

    thelonesomepine Busy Member

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    If your gun is producing 715 fps using a 8.4 grain pellet then you rifle is producing 9.53 ft lbs.:up:

    715 x 715 x 8.4 = 429429000 divide by 450240 = 9.53
     
    Last edited: Sep 27, 2009
  4. D4V1D

    D4V1D Posting Addict

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    Thanks for the straight talking guys :up:. Looks like my Air Arms needs a complete service. :D
     
  5. Oldguy

    Oldguy Active Member

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    Does anyone know if the weight of a pellet has any bearing on power i.e. ft lbs - My springer is showing 11 ftlbs through the chrono using Crosman Premier Hollow Points at 14.3 grains, if I used a lighter pellet say, would the power 'ft lbs go up or down?:confused:
     
  6. emin-j

    emin-j Engaging Member

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    Usually a bit higher with a heavy pellet,this is why it's better to not have your gun too close to the 12ftlb limit as if tested by the plod with a heavier pellet than you normally use it could take it OTT:eek:
     
  7. Patrick

    Patrick Donator

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    Depends entirely on the gun and pellet used there's no hard and fast rule,using a lighter pellet may increase muzzle energy if the muzzle velocity increases sufficiently which again would depend on pellet fit in the barrel etc.Using a heavier pellet sometimes will increase muzzle energy if it doesn't loose to much muzzle velocity,again depending on fit etc.
    I have had a couple of examples where a lighter pellet gave an increase in muzzle energy
    A Hatsan 60s that I owned produced 8.4 fpe with Gamo Pro Hunter pellets(15.43grns) and 11.3 fpe with BisleySuperfield(15.1grns).
    A .22 Scorpian that I owned with pellets weights varying between 14.6grns-16 grns produced about 11.4-11.6 fpe but with Superdomes(14.5grns) produced 12 fpe but they were not as accurate and lighter pellets shed their energy more the farther they travel.
     
    Last edited: Mar 6, 2016
  8. splat

    splat Donator

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    Just double checking...if you got combro new, that you put calibration number in on first setup..hth
     
  9. terry1001

    terry1001 Major Poster

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    If you go the the conbro website there's some videos which may help. You can never be certain of the effect of pellet weight but the general rule is that in a springer lighter pellets produce more power but in a pcp heavier pellets give more power - the only way to know for certain is to try.
     
  10. Dag

    Dag Very Active

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    Just personal choice but I never use the feature on Combro that allows you to input weight of pellet. I use the readings for ft/sec or fps and then calculate the mean average* from a string of readings and then finally using the aforementioned formula calculate the ftlbs or fpe
    I started doing this when I realised the Combro does not allow you to input weights to a second place of decimal, for example JSB Exacts in .177 are 8.44gn not 8.4.
    The result you would get would be slightly lower than it should be, which might or might not be significant if you are running close to 12ftlb
    Dag
    * I do knock off any exceptionally high or low reading but if I do so I take off the reading at the opposite end of the string to compensate.
     
  11. Patrick

    Patrick Donator

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    I think rounding up or rounding down is accurate enough e.g 8.44x800fpsx800fps=11.99ftlbs
    8.4x800fpsx800fps=11.94ftlbs
    I suppose if you wanted to play safe you could always round up and not down but bear in mind even with the best quality pellets there will be variations in pellet weight with pellets from the same tin so to get a truly accurate reading you'd have to weigh each individual pellet and make sure they're all the same weight.I think with the Crombro you have the option to enter the pellet weight in grams instead of grains which I think allows you to enter the weight to two decimal places,someone will correct me if I'm wrong.
     
  12. Dag

    Dag Very Active

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    That's a good point Patrick.
    I guess I find having to change pellet weights a bit of a faff and have actually forgotten to do so when checking a variety of pellets. It did come as a shock when I got a power of something like 20ftlbs when using .177 JSB Exacts only to remember I hadn't changed the weight from when I had run a string of .22 pellets through another rifle! :eek:
    Dag
     
  13. terry1001

    terry1001 Major Poster

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    I have weighed AA Field in .177 and found that there can be a difference of 0.7 grains between lightest and heaviest and others have had similar results so an error of up to 0.04 gn when you enter the weight isn't really very much. I suppose if you wanted to take the trouble you could enter the weight as 84.4 gn and then divide the power reading by 10 to get an answer.
     
  14. oliver13

    oliver13 Donator

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    There's a lot of handy stuff on the web which can help, type convert grains to grams into Google for instance, or Joules to foot pounds which is handy now & then; & go here to work out power with a couple of clicks: http://www.airgunsofarizona.com/energycalc.htm

    Nothing wrong with working stuff out, but if you're using a calculator you might as well use your phone, assuming you've got an Android handset you can do the same with a conversion app. & you can get the Chairgun app for it too which is all sorts of useful. A bit easier to haul down the range than a laptop too.
     
  15. TORNADOS7

    TORNADOS7 Pro Poster

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    As a general rule of thumb springers usually react positively to the use a lighter pellet by showing an increase in power, PCP's usually react positively to the use of a heavier pellet by showing an increase in power but that is not 100% a forgone conclusion as metallurgy amongst other things has a big part to play in whether the pellet causes an increase or decrease in power much the same as the effect it has on accuracy !...;):up:
     
  16. Jester

    Jester Engaging Member

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    That variation seems a bit OTT even taking into account pellet fit given the similar weights. Something other than pellet choice affecting those readings...?
     
  17. Patrick

    Patrick Donator

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    Both pellet types were weighed and were shot over a Chrony F1 and the muzzle energy calculated using the normal formula i.e weight x fps x fps/450240 so you tell me unless it was just an isolated case as I only tested about 10 of each pellets for velocity.
     

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