Quantcast
  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Do you trust your chronograph

Discussion in 'Handloading and Reloading' started by atblis, Oct 26, 2009.

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

    atblis Member

    Joined:
    Feb 19, 2005
    Messages:
    4,531
    Location:
    Neither here nor there
    Just wondering if you guys have any insight as to how accurate chronographs are.

    Specifically, have you ever done a comparison, like line up three different chronographs, one after the other?

    I am not entirely sure I trust mine. It definitely "shifts" after it has warmed up. But that's reasonable for electronics, digital scales are the same way.

    I have one of these.
    http://www.midwayusa.com/viewproduct/?productnumber=852429

    Sometimes I wonder.
     
  2. Ed Harris

    Ed Harris Member

    Joined:
    Feb 14, 2008
    Messages:
    247
    Location:
    Almost Heaven
    Normal industrial procedure is to fire a calibration check with reference ammunition on each setup to be sure that everything is working normally. I fire a few shots of Eley Tenex through my .22 rifle and if it is averaging 1080 +/- 15 f.p.s. sample average, as corrected for the ambient temperature, all is well.
     
  3. Shoney

    Shoney Member

    Joined:
    Jan 1, 2003
    Messages:
    1,292
    Location:
    Transplanted away from MT
    Some time ago, I thought my velocities were getting much higher than book data, yet showing no pressure signs at max loads. Since I didn't understand what was going on, I called the chrono factory.

    The chrono company asked what elevation I was shooting at, because at higher elevations the air is less dense and higher velocities could be expected. Since I wasn't at high elevation, they told me to calibrate my chrono using high quality .22 LR, where the expected velocity is on the box (Federal 900B for example).

    The quality ammo was to be fired out of a 24" bolt action or lever action .22, and should achieve the stated velocity within 50 fps or closely thereabout. The .22's usually vary less from the stated velocity than most commercial and handloaded centerfire cartridges. I was also told that the escaping gasses with unburned powder and residue particles of the cenerfire ammo crossing the chrono can give false high readings.

    I run 10 shot strings of high quality 22 ammo across my chrono about twice a season, and that reasures me I am in a very good ball park!:)
     
  4. ole farmerbuck

    ole farmerbuck Member

    Joined:
    Jan 16, 2009
    Messages:
    2,111
    Location:
    Western Ks
    I have a Shooting Chrony Alpha Master Chronograph and my neighbor has about the same thing. We lined them up and got different readings. I dont remember what the numbers were though.
     
  5. snuffy

    snuffy Member

    Joined:
    Apr 4, 2004
    Messages:
    2,896
    Location:
    Oshkosh Wi
    Yes I do! Mines a Pact standard chrono, I've had it for 12 years. If I ever wonder if it's accurate, I run a few rem. standard velocity 22 rimfire rounds over it. IIRC those should be right at 1250 FPS., they usually are right on.
     
  6. helg

    helg Member

    Joined:
    Jan 2, 2009
    Messages:
    277
    I prefer not to rely on anything, even on forum advices, if I have not verified the claim myself.

    My digital scale is accurate, and shows the same weight right after opening, and after a while, when it, like you said, "warms up". I have tested and verified this. I do understand how digital scale works. This helps me to get confidence in the scale.

    Same with chrony. Before relying on its data, I used to conduct tests on it. Airsoft rifle with a simple homemade ballistic pendulum. Shooting at close distances, shooting aside of the sensors, or not straight over the sensors. Time stability of the device. A lot of things to play with. It adds some fun to the boring process of just punching targets.

    Chrony relies on time measurement. Accuracy of the time measurement is far superior to the 4 digits that chrony gives you. Your watch does not drift when you wear it on your warm wrist or keep in a cold place. Non-straight shot is the first factor of discrepancy, straight cosine calculation gives a perfect estimate for that. Device vibration also can be estimated, but not that straight.

    Muzzle flash, or sky, which is not clear, causes the device not to catch bullet at all, or to give unrealistic data. Different loads and guns distinct in the flashes, this may require some time to get confidence.

    Try to make feel of your chrony, test it, and you can rely on it.
     
  7. Asherdan

    Asherdan Member

    Joined:
    Sep 20, 2007
    Messages:
    527
    Location:
    Hoss Country /USA
    Yes, kinda. Was out at the club one day and some other members had their chrony's out. I had my .22 bolt rifle and talked them into letting me put a couple of reference shots over each one, mine included. All shots came out within 30 fps or so of each other across the 2 shooting chronys and the one guy's Pact. I keep the (now <) 100 count box of ammo separate in the range box and fire a check shot or two before a chrony session, same as I was doing before and as the other posters have recommended. Having checked mine against a couple other chronographs does quiet the mind on the matter, though.
     
  8. Steve C

    Steve C Member

    Joined:
    Jan 5, 2006
    Messages:
    4,696
    I shoot some factory ammo, usually .22lr over mine to check readings and its always been at expected velocities. There are some things that can throw the readings off like any light flashes, powder passing over the chrono but in general the velocity reading appear accurate with few surprises.
     
  9. The Bushmaster

    The Bushmaster Member

    Joined:
    Jan 29, 2005
    Messages:
    7,868
    Location:
    Ava, Missouri
    Yes...I sure do trust my 20+ year old Pact 1 chronograph. It has never varied more then 30 to 50 fps (1160 to 1190 from a 20" barrel) when tested with CCI Mini-Mags.
     
  10. ~z

    ~z Member

    Joined:
    Aug 19, 2005
    Messages:
    813
    Location:
    High plains of Texas
    I trust mine, it's a Oehler P35. How could I not trust it?
    ~z
     
  11. NCsmitty

    NCsmitty Member

    Joined:
    Jun 29, 2008
    Messages:
    5,325
    Location:
    North Carolina
    IMO, many chronographs are setup too close and often get errors or erratic readings because of that. I setup at a minimum of 15ft. Obviously the folks shooting howitzers can benefit from the extra distance to the screens because muzzle blast and spewed aggregate can give errors and variations in the readout.


    NCsmitty
     
  12. qajaq59

    qajaq59 Member

    Joined:
    Dec 7, 2005
    Messages:
    2,375
    Location:
    S. C. Florida
    If they are all so trustworthy, how come people keep shooting them? :evil:
     
  13. Ol` Joe

    Ol` Joe Member

    Joined:
    Feb 25, 2004
    Messages:
    2,087
    Location:
    michigan
    I`ve both a Pact M1 and a old Shooting Chrony. I once taped the shooting chrony on top of the Pact screens and shot over both at the same time. The results were within ~2% max of each other. I feel this is fairly good accuracy from both units.

    DSC00911.jpg
     
  14. MCMXI

    MCMXI Member

    Joined:
    Jul 1, 2008
    Messages:
    7,490
    Location:
    NW Montana
    A couple of weeks ago I was using my chronograph and a friend showed up with his. After I'd finished shooting for the day, I let him use my rifle and my reloads and he shot five rounds over his chrono. I don't have the data in front of me but the average velocity that he got was close to the average I got but so what. Chronograph results are validated or corrected with field data.

    You need to validate measured average velocities by shooting targets at known distances. Chronographs are good for load development, but you simply can't beat getting real data in the field. I've shot close to 250 rounds of the same 178gr .308 Win load at 25, 100, 150, 200, 300, 400 and 600 yards over the past two weekends and that gives me a much better idea as to the average muzzle velocity. Field validated MV will be more useful (and more accurate) to calculate comeups out to 1000 yards since the local range only goes out to 600 yards. If you have access to a ballistics program, you can make small changes to the MV until the calculated comeups match up with actual comeups. Density altitude is important too and you should know what temperature, elevation and barometer values to input to get the same DA value.

    :)
     
    Last edited: Oct 26, 2009
  15. ants

    ants Member

    Joined:
    Nov 24, 2007
    Messages:
    3,710
    Do you trust your chronograph?

    I trust it not to shoot me.





    How many chronographs can say the same about us? :neener:
     
  16. jbkebert

    jbkebert Member

    Joined:
    Jan 30, 2009
    Messages:
    2,599
    Location:
    Kansas
    Not mine:D My chrono seems a little bitter with me since I stuck a arrow in it.
     
  17. bluetopper

    bluetopper Member

    Joined:
    Dec 17, 2005
    Messages:
    3,253
    Location:
    Northeast TX
    My chrony is bad about not displaying a reading at all.

    I use it under an awning in the shade. Is this OK?
     
  18. 1SOW

    1SOW Member

    Joined:
    Oct 28, 2007
    Messages:
    4,106
    Location:
    South Texas
    ants +1

    I started loading last year and borrowed a Chrony from a friend. I set it up carefully and it was a bright clear Texas day.

    I wanted aload that gave my 124 gr FMJ 9mm a 130ish Power Factor (speed x weight / 1000). I was meticulous. I was shooting from a good rest through the Chrony at a 25 yd bullseye target. After trying three different loads I was right in the ballpark! (big grin here)

    I later found competitive shooters who have their (same bullet) ammo checked regularly at major matches. Their load was NOT my load (similar guns/bbls). I had to be shooting light compared to their load. (big frown here)

    I need another chronograph to compare with my last results. I upped my charge on faith---I know, I know.

    I'm still trying to figure out how this is going to affect what chronograph I need to buy and how to check it. I need to be cost-effective as I don't load many variations.
     
    Last edited: Oct 26, 2009
  19. MCMXI

    MCMXI Member

    Joined:
    Jul 1, 2008
    Messages:
    7,490
    Location:
    NW Montana
    What sort of error messages are you getting? During my last session, the chronograph worked great when the sun was out and bright. Once the chronograph was in shade I started to get more errors. I probably should have removed the screens at that point but didn't. The sensors work off contrast i.e. a dark bullet moving across a light background. If the background is too dark, the sensor isn't going to detect enough of a difference and will give you errors.

    :)
     
  20. atblis

    atblis Member

    Joined:
    Feb 19, 2005
    Messages:
    4,531
    Location:
    Neither here nor there
    Also make sure the sensors are clean. That helps.
     
  21. helg

    helg Member

    Joined:
    Jan 2, 2009
    Messages:
    277
    Chrony works the best if it sees clear sky with no direct sunlight falling on its sensors. Mine does not work any good under a tree shade, ether directly under trees or under a tent that is not in a clear area. Light intensity fluctuates with the tree leaves in vicinity, and chrony can not set clear zero on brightness to catch its fluctuations from flying bullet. If your awning is away from tree shade, I believe that chrony should work. Just put its white screens on top to show to it dark bullet on the white screens instead of not-so-white ceiling.
     
  22. Radaray

    Radaray Member

    Joined:
    Jun 23, 2009
    Messages:
    64
    "If they are all so trustworthy, how come people keep shooting them?"

    Hahahaha. That's the best quote I've seen on here. Very good question!

    I believe the statement above is correct. They are useful for load development, as the readings should be construed as relative to what went before. Trying to achieve some manual stated velocity for a given load is not practical. They are extremely helpful when it shows a decrease in velocity with an increase in charge. This is a good indication that you have already reached your maximum load without reaching maximum pressure.

    Read velocities are good enough to get you in the ball park for range adjustments, but nothing beats trial and error~~~unless you are a sniper.
     
  23. helg

    helg Member

    Joined:
    Jan 2, 2009
    Messages:
    277
    I never heard about this. Does it mean that at some point muzzle speed decreases with increase of powder weight under a bullet? Are there any references explaining this?
     
  24. snuffy

    snuffy Member

    Joined:
    Apr 4, 2004
    Messages:
    2,896
    Location:
    Oshkosh Wi
    While not a reference, I just had that very thing happen here;

    http://www.thehighroad.org/showthread.php?t=482323

    It has to do with an extreme pressure spike caused by exceeding the normal expansion rate. A steady push is always better than a high peak then lower pressure. I've know about this for years, had it happen many times during wildcatting for handgun silhouette.
     
  25. MCMXI

    MCMXI Member

    Joined:
    Jul 1, 2008
    Messages:
    7,490
    Location:
    NW Montana
    Here's a comparison between the same load fired over two chronographs a couple of weeks ago with 2 hours elapsed between the first and second five-shot groups. The load consists of Lapua cases, CCI 200 primers, 168gr Nolser HPBT bullets and 43.5gr of Reloder 15. The weather changed considerably between the first and second groups (raining and cloudy vs. dry and sunny). Despite that, the average velocity of the second group is only 0.6% less than the average velocity of the first group.

    Code:
    	(fps)   (fps)
            2768	2764
    	2766	2771
    	2783	2761
    	2777	2753
    	2793	2750
    		
    Avg.	2777	2760
    ES	27	21
    SD	10	8
    Hi	2793	2771
    Lo	2766	2750
    
    :)
     
Thread Status:
Not open for further replies.

Share This Page