1. Attention: We have put together a thread with tips and a tutorial video to help with using the new software. Please take a moment to check out the thread here: Trapshooters.com Tutorial & Help Video.
    Dismiss Notice

Chrographing shotshells

Discussion in 'Uncategorized Threads' started by BAP, Feb 14, 2008.

Thread Status:
Not open for further replies.
  1. BAP

    BAP TS Member

    Joined:
    Jan 29, 1998
    Messages:
    231
    Would some one with experience in shot gun chronographing please give some pointers on the proper way to do this. I know the non commercial units measure the leading pellet and not the central mass. I understand that the reading will be 30 to 50 fps faster that the factory settings. What distance should you be from the 1st screen and do you need to use a bench or will off hand affect velocities very much? I am trying to use a ProChrono I believe it is called that was purchased from Frigon many years ago. I know it's not a upper end unit but will it give reasonable data. I tried it without the covers the other day and velocities were ranging from 500 to 1600 fps. Thanks, Bill Parson Jr.
     
  2. Dr.Longshot

    Dr.Longshot Banned Banned

    Joined:
    Jan 29, 1998
    Messages:
    5,722
    You need the screens on, fresh batteries, and from a bench, about 3 feet from the first screen, center the shots thru the opening.


    Gary Bryant
    Dr.longshot
     
  3. A23B

    A23B TS Member

    Joined:
    Jan 29, 1998
    Messages:
    44
    I use a Pro Chrono for all my shot shell testing.
    While it is not the best unite on the market it is quick and easy to set up.

    What I do is make sure the battiery is charged remove the sunscreens and keep the end of the barrel about four feet away. I have found the bright sunny days work best. If I get any reading that are why off I just disregard them.

    With my unite using factory shells as abase line, I have to remove 20 FPS from all readings

    -=ed nast=-
     
  4. zzt

    zzt Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    3,462
    Location:
    SE PA
    I also use the Pro Chrono Digital. I get very consistent results after implementing the suggestions I received from Bob Dodd. I'll also pass on a few other tips.

    Bob suggests placing the chrono in deep shade with the sensors pointing to clear sky. That is the most important tip. Any sunlight hitting the sensors, even at an oblique angle, affects the results. If you cannot place the unit in deep shade, shade the sensors with a box to keep sunlight off of them. Using the diffusers supplied is generally a good idea. Sun high in the sky gives the best results.

    The Mfg says to allow 8' between the muzzle and the first screen. I use 6' and have zero problems.

    A bench or a rest is a must. You must fire over the chrono on-axis and at the same height above the sensors each time if you want the best results.

    A full choke will give you readings that are 20-30fps high. A .018 choke will give you readings that are 10-20fps high. If you have choke tubes, use the most open you have.
     
  5. Neil Winston

    Neil Winston Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,848
    Bill the link above will get you working. I like a full canopy or a cloudy day. Clean the lenses with a Q-tip. The reading you get will depend on the gun you use. If you are try to "calibrate" with factory shells it's probably not going to give you much, they vary too much lot-to-lot. As zzt says, six feet is about right. If you use a lower barrel or high rib or unsingle, do the geometry first!

    Neil
     
  6. shot410ga

    shot410ga Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,784
    I have the same unit. I use the shades each time. Shoot at about 3-4 feet away, off hand in the shade below some trees. My unit will chrono 1250 +/- 10fps for 3 dram AA's and 1200fps for STS 2 2/4, +/- 5fps. That's what the box says they should be. I also reload to those speeds. And my reloads are very close +/- 10fps. The machine may be high or low, but it's consistant. My old Sheridan Pellet gun was about 720fps with 10 pumps +/- about 10fps.
     
  7. BDodd

    BDodd TS Member

    Joined:
    Jan 29, 1998
    Messages:
    3,594
    ZZT has pretty well outlined my recommendations. The distance between muzzle and first screen MAY be different from one brand of chrono to another. I use an Oehler and it needs 6' to the start screen at a minimum and I use 7' to ensure no disturbance errors caused by muzzle blast. I DO shoot across the screens off hand, maybe sitting which keeps the chrono lower to the ground for stability on photography stands.

    One thing I have come to understand is that any homeowner chronograph is likely best used for comparison purposes rather than data that approaches the exact speed as will be gotten from high grade commercial test barrels and chronographs. Here's how I deal with that: I recommend using your gun, your barrel, your chosen choke and on the same day, same temperature, same equipment set up testing some factory shells across your chronograph and then comparing your reloads to those results. For example if you run 1200 fps factory shells and get readings of, lets say, 1260 fps with your full choked, 34" Acme ClayBuster but only get 1200 fps readings with the same equipment on the same day with your reloads you can see that you're not loading to the same performance as the factory load you are trying to match.

    I have the pleasure of having an O/U with 28" barrels and skeet choke tubes that comes VERY close to exactly what is published for factory shells and it is this gun I use for chronographing. This gives me some feeling that not only am I matching a factory load (or between some shells or other comparisons) but I also have the idea that the data is pretty close to what a test barrel would produce.

    Last, don't forget we're chasing clay birds leaving the trap house at approx. 42 MPH and using shells with the velocity from the muzzle of 775 to 825 MPH (generally) and, therefore, some wiggle room is built into our concern for just how critical are our needs for exact velocity readings. The chrono should be used to comparisons and test for consistency in groups of significant size rather than to find precise velocities....breakemall....Bob Dodd
     
  8. whiz white

    whiz white Strong Supporter of Trapshooting Banned

    Joined:
    Jan 29, 1998
    Messages:
    4,771
    Location:
    Rapid City SD
    I like Einstein's theories, it's all relative.

    I have chronoed shells for years. Forget about the mass center, shot string, where to stand, etc. Incidentally, your ProChrono is just fine.

    Take a new factory shell that you like, shoot it and record the results. I would do this a mininum of 5 times for each load to narrow down the standard deviations.

    Take your reloads and stand in the same way, the same distance from the screen as you did in the new shell shot, and record those statistics.

    All you care about is your reload compared to factory shells anyway.

    I am at H-S Precision here in Rapid City often. They make most of the test barrels for all of the shell manufacturers and do armor plate testing for the US and other governments. They test these barrels for pressure and fps with an enormous Ohaus electronics setup in a separate room. I have even worked in that room during some State Department armor plate testing and for some foreign governments. They do it the same way that I have done my testing with my little portable chronograph, although my chronograph, of course, does not do the pressure testing, and it not accurate to 4-5 decimals.

    We can argue 'till the dogs come home about center mass, bullets versus pellets, haw far back to place the barrel, etc., but we're splitting hairs here.

    Just do the relative comparisons with factory loads and your loads and study the results. H-S simply has their barrel holding block placed statically and each test barrel is inserted the same way each time and the results are recorded accordingly.

    To shirt-tail quote Bob Dodd above: We're not trying to shoot through the eye of a needle at 100 yards moving 100 mph. It's clays shooting.

    IMHO.

    Whiz White
     
  9. shot410ga

    shot410ga Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,784
    whiz white: That's what I was trying to get across. I just compare my reloads to factory shell at the same time, to see if they are close. Perhaps, it makes no differance if the chrono is a little off, as long as it give a comparison.
     
  10. BDodd

    BDodd TS Member

    Joined:
    Jan 29, 1998
    Messages:
    3,594
    And, shot410ga, as long as you do the comparison with the same gun, barrel, choke, on the same day, same weather and so on.
     
  11. BAP

    BAP TS Member

    Joined:
    Jan 29, 1998
    Messages:
    231
    Thanks, everyone. I just want getting consistent readings to support any test I was trying to do. I wanted to see what differences the cheap primers make as far as velocity and consistancy. I appreciate the help. Bill
     
  12. BDodd

    BDodd TS Member

    Joined:
    Jan 29, 1998
    Messages:
    3,594
    Dixie, I predict very little difference....Bob Dodd
     
  13. Capt. Morgan

    Capt. Morgan TS Member

    Joined:
    Aug 27, 2007
    Messages:
    1,061
    From the tests I've had done, I predict a measurable difference in velocity but far more significant differences in the loss of consistency and in the increase in peak chamber pressure (which you can't measure with your equipment) depending on which premium primer you're comparing to.

    The link above is to an article by Tom Armbrust comparing several bargain primers to one premium primer.

    Morgan
     
  14. BDodd

    BDodd TS Member

    Joined:
    Jan 29, 1998
    Messages:
    3,594
    Sir Morgan's right enough. It's a flaw in my thinking about reloading and chrono work to rarely consider pressure differences since I load so light; 1 oz and 7/8 oz loads WELL under significant pressures concerns and, thus, I fail to bring up the pressure changes with substituting primers. My failure and the lame excuse for it. Anyone already loading fodder that is rated, with known components, as high pressure loads, should give much thought about exchanging primers willy nilly....Bob Dodd
     
  15. airborne

    airborne TS Member

    Joined:
    Jan 29, 1998
    Messages:
    34
    I was getting 50 to 70 fps differences in 5 shots and didn't know why. A friend said to use once fired shells in stead of the ones I just grabbed out of the box, some of which had been loaded 8 or 10 times. The readings went down to 10 to 15 fps difference. Jack A
     
  16. airborne

    airborne TS Member

    Joined:
    Jan 29, 1998
    Messages:
    34
    I was getting 50 to 70 fps differences in 5 shots and didn't know why. A friend said to use once fired shells in stead of the ones I just grabbed out of the box, some of which had been loaded 8 or 10 times. The readings went down to 10 to 15 fps difference. Jack A
     
  17. Paladin

    Paladin Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    4,398
    The renowned (if that adequately describes him) Ken Oehler, whom most consider the father of the modern chronograph, wrote articles in Shooting Times magazine for about 2 years. If you can find it, the January '07 issue published one of his articles titled 'Chronograph Light'. It goes into detail about the affect that light variation has on light triggered chronographs. IMHO all of his articles are priceless and may be without equal.
     
  18. BDodd

    BDodd TS Member

    Joined:
    Jan 29, 1998
    Messages:
    3,594
    Airborne, I've had just the opposite results. In a convoluted test of well worn shells vs once fired shells and also those with independently hand weighed powder and shot charges vs. those cranked through a hydraulic MEC at warp speed had the well worn hulls rushed through the loader producing the lowest standard deviations of the 4 possibilities. Now, I admit the differences were not terribly significant and the results might have been in a different order if done several times but I was satisfied that the condition of the shells and how they were loaded (in my routine) didn't make enough difference to consider in the future. Now, I have seen 50 and 70 fps differences pop up when I had the light screens out in direct sun and I eventually opined the direct sun light was causing the problem with reflections off pellets. No suitable test I've settled with has had that kind of inconsistency....breakemall....Bob Dodd
     
  19. Neil Winston

    Neil Winston Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,848
    Airborne, I'm with Mr. Dodd. Reloads don't start to have variability problems until they look terrible. Six, eight reloads should be indistinguishable from factory. This is, of course, contrary to the the many articles you have no doubt read "Shotshells lose 10 fps per reload" and so on. They are hogwash.

    Dixie Trap you can't tell about variability (your cheap vs dear primer test) until you get a dead-solid baseline which will include, at the very least, testing with a cylinder choke, a canopy light diffuser for the chronographs, and two chronographs measuring the same shot. Nothing less will do. And even then you will get no closer than better than average, average, or worse than average. And to get those groups you will need a lot of data before your even start to test primers. Even then, your results probably won't single out the primers as the "cause" since variability is the rule, not the exception.

    Neil
     
  20. zzt

    zzt Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    3,462
    Location:
    SE PA
    The manufacturer's rep for the second chrono I'm planning to buy confirms Bob's experience. He says he is repeatedly told by users the SDs go lower, the loads are more consistent, after the hull has been reloaded 4-5 times. That makes a certain amount of sense. When the weather warms, I plan to test that assertion.
     
Thread Status:
Not open for further replies.