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Chronographing Question

Discussion in 'Uncategorized Threads' started by ec90t, Feb 4, 2008.

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  1. ec90t

    ec90t Guest

    Just a thought that has been rambling through my head for a while. I have seen a lot of discussion over the years on this site about chronographing shot shells and the shot string being measured etc.

    Question is:

    Can you get an effective measurement of shell speed by substituting a slug in place of the shot and using a suitable open choke. I would think that this way a true shell speed could be established and a lot of variables could be eliminated. I've never seen this idea talked about before.

    ec90t
     
  2. Paladin

    Paladin Well-Known Member

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    ec,

    I don't believe substituting any component will give you the end result you are looking for. Just as the reloading manuals show, there is a change of pressure and velocity with just a wad change only. Even using the same wad, a slug sitting in there instead of shot will surely have some affect on the sealing ability of that wad. A crimp of some sort, which also affects pressure, would be very hard to duplicate I think.
     
  3. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    I've never chronoed the slugs but I'd think 7/8ths or 1 oz at specific book velocities such as 1150 or 1200 would be just that? Whether it's pellets or a slug measured a few feet in front of the muzzle. Hap
     
  4. g7777777

    g7777777 TS Supporters TS Supporters

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    no- and why would you want to? you want the exact components that you are going to use/test

    Gene
     
  5. halfmile

    halfmile Well-Known Member

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    you can get the stuff you need from Ballistic Products if you want. I would have better things to do. A crimp over the top of a slug is and anomaly and would affect things to some degree.

    The simple way is to deduct 30 FPS from your chronograph reading to approxiamte the inductive shield readings industry uses.

    HM
     
  6. ec90t

    ec90t Guest

    Thanks guys.

    I was just thinking that substituting a solid payload for a loose payload would be just the ticket in measuring shotshell speed using a canopy styled chrono'. This way the leading pellets and muzzle blast could be eliminated and the shadow would be much more pronounced. This would give the truest readings possible.

    ec90t
     
  7. IM390

    IM390 Member

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    Truest readings don't mean crap, if you are unsure of how to interpret them. Fast and slow pellets, long strings of pellets are for philosphers. Take a distance that you a shooting like 35 yards for 16 yard trap and keep the chronie 10 feet in front of the muzzle and measure the test.
    PERIOD! If you do this you will get all the info you will ever want to know. Remember 1045 fps is 700 mph and the average target is only traveling about 40 mph when you are pulling the trigger.
     
  8. redhawk44

    redhawk44 Member

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    You can chronograph shot charges and get pretty accurate results if you do it right.

    First, unlike chronographing rifle or pistol ammo, you need to get close to the 1st screen.....within about 3 feet. This in itself causes a problem with muzzle blast damaging the screen(s) and also with the blast tripping the first screen resulting in a faulty reading. Soooooooo.

    What you need to do is fasten a piece of plywood in postition just ahead of screen #1 and cut a 3" or 4" hole in it to shoot through. That protects the screen and blocks the muzzle blast. You also need another piece of plywood just in front of screed #2 to protect it from stray shot and such. That one can have a larger hole in it.

    I use a Pact model 1 and chronograps everything new that I load (at least 10 shots). Sometimes I pattern at the same time.

    The results are typical velocities that are not that far from what the data says you should get, and are also consistent enough that I trust the system....although I am willing to agree that I can't actually PROVE that it is accurate.
     
  9. phirel

    phirel TS Member

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    ec90T- I would think that barrel friction would be different between shot and a slug. I chronograph primarily to test the consistency of my reloads. I believe this is a measure of the quality of components I use. I am not overly concerned about the actual velocity. I load under the legal ATA limits so velocity is not a major factor.

    On the other hand, shells that test very inconsistent in velocities (some discount brands) seem to work very well.

    Pat Ireland
     
  10. zzt

    zzt Well-Known Member

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    The results I get are opposite to redhawk44's. I've found that putting a minimum of 6' between the muzzle and the first screen gives the most consistent results. Using a full choke increases the velocity returned. Using an .018 choke gives me just about published velocities with 6' between muzzle and screen.

    Like Pat, I'm more interested in consistency of performance. I don't give a hoot if the velocity averages 1147fps or 1154fps. I do care is the SD goes from 9 to 18.
     
  11. Paladin

    Paladin Well-Known Member

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    Ken Oehler says use 5' to 7' distance from the muzzle to the first screen, with a shotgun.
     
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