cronoitis?

Discussion in 'Hunter (HFT) & Field Target (FT)' started by Suzukiphil, Jun 30, 2014.

  1. Suzukiphil

    Suzukiphil Member

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    Hope you good people on here can give me some advice. In the last two GP's my ev2 has been crono'd at 795 at Bolton, near the end of my 50 shots so I crono'd it with my combro when I got home it was running 750-760, but I turned it down a bit on the side port to avoid any danger of going over power. yesterday it ran over the crono at 796.
    Tonight I've shot 50 shots through my combro with the EV and not registered on shot over 740fps! Using Molly's protarget as a reference, (it was crono'd in both gp's at around 764) tonight using the same crono and the same pellets all the shots registered around 764 give or take 5fps.

    So, does anyone have any idea how my EV that is running below 740fps over 50 shots can register 795 &796 when measured on the BFTA crono????:confused::confused::confused::confused::confused:
     
  2. Yorkshiretea

    Yorkshiretea B Grade Bandit

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    Puzzling, wonder if it's a hammer problem but that's just a guess.
     
  3. gavin hopps

    gavin hopps GP 2015 C GRADE CHAMP

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    I was going to say your combro may need recalibrating, but if your mates gun is the same over the gp crono and your combro then it cant be that.
    Its stumped me.
    Is it if you leave it for a while then it jumps of just now and then?
     
  4. Suzukiphil

    Suzukiphil Member

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    it is quite consistent probably 12 fps max variance over 50 shots, nothing to suggest a sudden jump in power of 55fps!
     
  5. Ratinator

    Ratinator 77.74

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    Reference point's

    Phil are the pellets landing where they should when you dial the long one's or are they dropping low?
    If i was you i would set the gun up at 785 on the bfta chrono and be done with it if your clicks are working.
    Maybe that muzzle blast is playing tricks with yours,if i remember rightly Mollies gun has a silencer fitted.
    At 740 i would expect the long one's to be well low,if they are not then it's the chrombo
     
  6. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    The thing to try next is to take your combro down to the club and check the reading on the combro against a club chrono to see if they read the same or thereabouts.

    From the sounds of it, you want to rule out a misread on the combro before you start coming up with other theories.

    Checking another gun on the same combro goes some way toward suggesting that it isn't a misread, but it doesn't rule it out completely.
     
  7. Suzukiphil

    Suzukiphil Member

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    that might be a good idea. I thought I'd just turn it down 10fps regardless of what my combro said. but it is running around 10ftlbs! Muzzle blast might be a possibility, but I tried it from a couple of feet away yesterday, shades on shades off, in the tent out of the tent, most of the time it didn't register a shot!
     
  8. Tench

    Tench WHFTA World Champion 2016.

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    I would suggest it is alignment of the combro when on your own rifle. if one sensor is seeing the pellets head and the other missing the head but getting the skirt you will get a difference this big as the sensors are only 50mm apart, so a 5mm discrepancy will produce the 10% error you are seeing. The combro is a great tool but very sensitive to alignment as it only has one a single light beam across each sensor.

    They also prefere to be used on a silencer which helps to dissipate the air blast, under some conditions the combro will see the air and give a false reading.

    As well as the normal adjustment of the mounting bracket you may need to pack between the gun and one end or the other of the mounting as I have seen ones that are quite distorted. A close fitting straight drinking straw inserted in the barrel or silencer can help as an alignment guide. McD straw is good in most silencers.
     
  9. Suzukiphil

    Suzukiphil Member

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    The combro is very consistent for the two guns over a full charge and was the last time. I wonder if anyone else has registered any strange numbers on the bfta crono?
     
  10. Suzukiphil

    Suzukiphil Member

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    wouldn't that produce inconsistent readings? which it isn't doing, 50 shots all under 740
     
  11. Tench

    Tench WHFTA World Champion 2016.

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    Inconsistent readings would only come from the combro seeing a different spot on the pellet each time, air blast may cause inconsistency but not misalignment.
     
  12. Suzukiphil

    Suzukiphil Member

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    I don't fix the combro onto the muzzle, I position it for each shot, so in theory every time the combro is realigned.
     
  13. Tench

    Tench WHFTA World Champion 2016.

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    I wouldn't trust it at all then! go with the clubs reading.
     
  14. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    That doesn't rule out that it's reading correctly for one gun, but consistently misreading for the other.

    The BFTA chrono has been spot on for me at every GP this season btw.
     
  15. neilL

    neilL New Member

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    I bought the simple alignment part for the Combro (looks like an easy 3-D print job but hardly expensive). When used the combro is much more consistent and if not used being slightly offset may explain the differences between the 2 guns.
    If anything the BFTA chromo gave my rig a slightly higher reading than on other chronos at previous events. As long as it passes I don't worry about the actual reading on the day. If the pellets match elevation clicks on the zero range a few fps won't make any difference.
     
  16. Suzukiphil

    Suzukiphil Member

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    Cheers Neil, Just been onto the combro site and ordered on and some new batteries. I agree with your second point, I have never had a gun run that close and when it was a little high or low, I've always put it down to heat or muzzle blast, or on the old bfta cronos changes in light levels, don't know much about these new ones so don't know if that might have an effect, but if it's ok for everyone else then I must be getting a false reading.. consistently!
     
  17. AndyIoW

    AndyIoW Member

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    This year I have taken my crombro to each go so far this year to compare what it reads compared to the bfta chrono.
    From memory and will change when I look at my records tomorrow as I made a note of the chrono number as well I hope.
    GP1 I forgot to check the batteries and they were flat. Doh
    GP2 mine 761 bfta 757
    GP3 mine 777 bfta 785
    GP4 mine 773 bfta 769

    I had mine set up by John Ostler for 770 when serviced nearly 3 years ago and not touched it since and come Winter and Summer it is with +/- 10fps of what I expect.

    If you can could you use your crombro and another type to compare results?
    Life,e Neil I use one of the alignment tools for consistent placement.
     
  18. sven

    sven Member

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    You did use exactly the same pellets for the BFTA chrono as you did with the Combro?
     
  19. RobF

    RobF Administrator Staff Member

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    Personally if I am seeing problems then I don't trust chrono readings from the muzzle. There's too much blast going on and if the chrono is seeing a pressure wave or looking through a pressure wave then it won't give you the right answer.
    When I set mine up it's done 2ft from the chrono. To give you an idea of the problem we were chroning .38 and .44 subsonic live 6-7ft from the chrono.
     
  20. Artfull-Bodger

    Artfull-Bodger Member

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    I gave up on the combro as it's too easy to get inconsistent results with them, especially with springers, your much better off using a chronograph like the Chrony or F1 with lights fitted for consistency!
     

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