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  1. #1
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    589

    Default Ballistics Chronograph

    I've been wanting some sort of instrument/device to check muzzle velocity of my elderly Diana 15 air gun as I go through the various stages of restoration - the Diana was given to me as a 9th birthday present, it was already 2nd hand when I got it - my older brother and I would regularly go through 2 packs of 500 Marksman pellets on a weekend, when we ran out we'd dig some pellets out of the chicken shed wall - straighten them as best we could using our teeth and then shoot them again.


    I gave some thought to a ballistics pendulum, then thought about possibly developing an arduino based chrono until I came across a HT-X3005 on Aliexpress - $34 delivered - in developing an arduino based chrono myself the cost of components alone would probably be double that.


    The version I bought comes in 2 sizes - mine is the smaller version - comes with internal rechargable battery, instructions, cable ties, a velcro strap, brass spacers and a second end cap. The business end (end cap) has a series of numbered holes - the idea is that when the supplied brass spacers - 3 of - are screwed into the correct holes, the spacers form a sort of tunnel that will go over the muzzle end of the gun under test with the muzzle centered over the central hole through which the pellet/bullet passes, the 'tunnel' formed by the spacers can range from 20mm up to 30mm in 'diameter' to cater for different barrel sizes, cable ties or a velcro strap secure the instrument to the barrel - a bit agricultural but in practice probably works ok, a screwdriver is included as the end cap needs to be removed to attach the brass spacers, a second end cap is also included to cater for barrel sized sizes from 16mm, up to 40mm, also included is a bit of plastic tube which I assume is meant to go over the brass spacers possibly the protect the finish on the barrel.
    How well does it work - so far yes, it does work - I haven't tried an actual gun as the package arrived rather late in the day but I couldn't resist blowing a 3/16 ball bearing through a small brass tube using the air line - the recorded 'muzzle' velocity was 61.6 meters per second or about 200 ft/sec

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    Screenshot 2024-05-09 231730.jpg

  2. #2
    Join Date
    May 2011
    Location
    Murray Bridge S Aust.
    Age
    72
    Posts
    6,019

    Default

    Pity this sort of technology wasn't around 40-50 years ago, when I was madly into shooting.
    Kryn
    To grow old is mandatory, growing up is optional.

  3. #3
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    589

    Default

    I was eager to test the chrono on an actual gun - no point in trying a .22 as the muzzle velocity of these rounds has been well documented for years - my well used Diana 15 won't even push a pellet out of the barrel, so I picked on a Crosman M1 carbine replica BB gun - these were made in the late 60's thru to the mid 70's, mine is the plastic stock version, it's a favourite of the grandkids, at the time they were sold the muzzle velocity was given as 350ft/sec be interesting to see how would be after 50 odd years. The first shot came up at 349ft/sec, a bit of a surprise given it's age, the second shot came up 176ft/sec.


    It seems I was a bit too eager - rather than rig up the brass rods/spacers I held the chrono in front of the barrel - not a good idea - the first shot was fine the second shot just grazed the side of the chrono central tube made of aluminium leaving a small mark, looking down the tube I could see 2 more marks where the BB bounced off the sides of the tube, I rigged up a series of pvc conduit one inside the other, and managed to get it stable and central to the chrono tube, subsequent shots saw the velocity spread from 370ft/sec to 337ft/sec - about what I would expect from a BB that has a loose fit in a barrel, not bad from a 50+ yr old air gun. A series of 3D printed adaptors to keep the barrel in line is probably the way to go.


    Something I hadn't noticed then I first tried the ball bearing in the brass tube a computer generated female voice speaks out the muzzle velocity - good idea as the chrono is hanging off the end of the barrel it negates the need to turn what could be a loaded gun back towards the user to see the display - the display also shows muzzle energy provided the correct projectile data is chosen and all shots are logged so one can go back through the data after the test firing. All I need to do now is find the time to spend on the Diana 15, I think the grandkids would like that as well.

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  4. #4
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    57
    Posts
    2,722

    Default

    Very interesting and thanks for posting.
    There are a number of higher end chronos used in the shooting world currently and the generally better ones are Doppler radar based.
    Looking at over $1K though - so a bit out of reach for your purpose.

    Iím tempted to buy one of these cheapies just to see how it copes with having a few .308 rounds poked through it

    Steve

  5. #5
    Join Date
    Sep 2010
    Location
    Lebrina
    Posts
    1,923

    Default

    Quote Originally Posted by OxxAndBert View Post
    Iím tempted to buy one of these cheapies just to see how it copes with having a few .308 rounds poked through it
    I think you should definitely try it out with the .308. That way I'll have a better idea if it's worth trying on a well stoked .375 H&H

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