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Chrony Speeds

Discussion in 'Shooting Related Threads' started by BD Trapshooter, Mar 16, 2009.

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  1. BD Trapshooter

    BD Trapshooter Member

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    Just wondering what some of you getting for accuracy with a Shooting Chrony. I have a new Beta model and chronographed some shells yesterday. They are a reload copy of the Winchester Super Handicap, Winchester primer, Winchester AA wad, Winchester Super Handicap hull, and the powder was Super Handicap (21.2 grains measured on a scale) 22 bushing on my MEC 650. A 23 bushing was dropping 22.0 grains. The shells chronographed at 1314 average. What do you think?

    Thanks,

    Dan McDermott
     
  2. Neil Winston

    Neil Winston Well-Known Member

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    I think you shot them through a full choke but unless we knew more about the SD that's about all I can say.

    Neil
     
  3. BD Trapshooter

    BD Trapshooter Member

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    Neil,

    They were shot thru a Beretta 682 Gold E 34" Top Single with a stock bore and improved mod choke.

    Thanks,

    Dan
     
  4. Neil Winston

    Neil Winston Well-Known Member

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    IM is close enough to full to add maybe 25 fps to the expected speed. I can't help noticing that you are loading more powder than the guide recommends, which is a max of 20.9 grains to get a predicted 1255 fps and 11,3000 psi. That taken into account, and still lacking the SD information I mentioned earlier - if the SD is low the crony seems to be doing it's job.

    Neil
     
  5. BD Trapshooter

    BD Trapshooter Member

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    Neil,

    Forgive my ignorance. What is SD?

    Dan
     
  6. Neil Winston

    Neil Winston Well-Known Member

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    Sorry, Dan, it's one of the things your Crony calculates - standard deviation - and is basically a measure of the variability of the readings. With a choke like IM, you really can't make much of an estimate of variability of your shells - the choke contributes too much to that statistic. If the SD is too high, say 20 plus, then you can't trust the reading much at all.

    My personal standard is under 8 is good, 9 to about 16 is average, and over 16 is a warning that something _might_ not be working as it should and a least a re-check could pay off.

    You might want to take a look at the linked file above.

    Neil
     
  7. hmb

    hmb Well-Known Member

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    Did you weigh the shot charge? HMB
     
  8. g7777777

    g7777777 TS Supporters TS Supporters

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    Chrony is probably right on- in reviews- they have been rated as in the top 2

    Looks like you are beyond max load?

    Gene
     
  9. Just-A-Shooter

    Just-A-Shooter Member

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    Neil,
    Why does the full choke add so much? I have just ran a ten shot set and my results are; 1183, 1182, 1204, 1188, 1195, 1185, 1183, 1195, 1193, and 1172.
    The load was 1-1/8 oz of reclaimed shot, 16-1/2 grains of RedDot, Blue Duster wad, Federal 209A primer in an old style AA hull.

    I usually shoot full choke so I ran this test with it. Why not test the gun and choke that will be used with the reloads.
     
  10. Neil Winston

    Neil Winston Well-Known Member

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    A choke speeds up at least some of the pellets and the chrono notices it; that's why the speeds are higher than with cylinder, which doesn't speed the shot up. It's been explained as like a garden hose squeezed at the end getting more distance (resulting from more velocity).

    Your SD of 9 is fine.

    I use two chronographs lined up one after the other when I test outside. When a cylinder choke is used, the two readings for a single shot are 2,3,4 fps different; sometimes one is consistently faster, sometimes not. When I use a full choke and a similar setup, the reading are often 10 or 20 fps from one another, first one high, then the other all mixed. This tells me that the general belief that these chronos "read the first pellet" is not right; they read however-many they need to get a reading. And the shot coming out of a full choke is more strung out, so now "this many" works for this chrono, "that many" works of that one on this shot.

    So if you want to know the variability of the shells, more open is the way to go, since there is less added measurement variability.

    But even then, this estimate of variability is dicey; that's why I just use broad categories. The reason is "regression to the mean." Even if you get a low SD, you will more likely get an average one next. High SD's don't necessarily work that way. Rifle shooters say "Good groups sometimes repeat, bad groups always repeat" and the same holds true of shotshell speed, for the most part.

    Certainly if you tested two loads and one ten-shot string gave you an SD of 5 (good) and the other 10 (average) you would be going way beyond your data to say that one was more consistent, generally, than the other, since if you did the first good one again, you might well get a 10 - or more. If you can keep your reloads under 12 most of the time you are doing very well, as well as the factories, again, most of the time.

    Neil
     
  11. K-80BUD

    K-80BUD TS Member

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    I have a Chrony which I had no confidence in. SoI purchased an Oheler model 33 proof channel chronograph. This is the one that gives you two readings per shot string. For a lark, I put the Chrony in front of the Oheler and took 20 readings.When the readings were corrected for distance from the muzzle, the readings were within 1 percent average. I now believe in the Chrony (although I don't use it much.)
     
  12. Michael Jobe

    Michael Jobe TS Member

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    How far should the chronograph be from the muzzle? 10', same as with a rifle?

    I run the same load as the original poster and want to compare my reloads to factory Super Handicaps and adjust accordingly. I know I'm flirting with max pressure, but it also sounds like I'm over max velocity for 1 1/8 oz loads.

    ~Michael
     
  13. Just-A-Shooter

    Just-A-Shooter Member

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    Michael,
    Shooting Crony recommends 5 foot for shotgun.
     
  14. jbrucejr

    jbrucejr Member

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    Just-A-Shooter

    I noticed that you said you load reclaimed shot.

    You have to remember that it is a mix of sizes so not every drop will weigh the same. You may dump a batch into your loaders shot tube that is "rich" in 9's and get a heavier drop than what you would get with a batch that was "rich" in 7.5's.

    This could easily account for the variability of the velocity - - but what you show is not all that bad. I would expect it to have less varibility with new shot.

    John
     
  15. Just-A-Shooter

    Just-A-Shooter Member

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    Jbrucejr
    I have not been weighing the shot drop. I have just trusted the Mec charge bar. The next time I reload I will confirm what I am really dropping for shot. Thanks for the heads up.
     
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