chronograph accuracy and testing

6

6724

New member
i see many guys posting on here about their pet loads and often the velocities are far higher than what i get. it makes me wonder if these "home owner" type chronographs are accurate and consistent.
it makes me wonder if my chronograph reads low, is there a way to check it?


also, i load for max accuracy not max velocity. i rarely find great accuracy with at or near maximum loads. my accurate load in my 24" barreled ar15 with a 55gr v-max is 25.5gr of 748. according to my chronograph, it is running 3050fps. it groups, in cold weather, around 1/2" sometimes much less. but then i hear of people running the same bullet out of a 4" shorter barrel at 3300fps, are people running bullets that fast getting superb accuracy?

my chronograph is a shooting chrony f1.
 
Originally Posted By: 6724i see many guys posting on here about their pet loads and often the velocities are far higher than what i get. it makes me wonder if these "home owner" type chronographs are accurate and consistent.
it makes me wonder if my chronograph reads low, is there a way to check it?


also, i load for max accuracy not max velocity. i rarely find great accuracy with at or near maximum loads. my accurate load in my 24" barreled ar15 with a 55gr v-max is 25.5gr of 748. according to my chronograph, it is running 3050fps. it groups, in cold weather, around 1/2" sometimes much less. but then i hear of people running the same bullet out of a 4" shorter barrel at 3300fps, are people running bullets that fast getting superb accuracy?

my chronograph is a shooting chrony f1.

There are a few things that no one questions in shooting. One them is their chronograph. People swear that if it says they are getting a 12 SD then that is what they have...

... some years ago, a friend and I lined up 4 chronographs in a row, and shot through them.

You would expect that they would be the same, less a few feet per second because of velocity loss between the individual sets of traps.

No way, Fuzzy José.. they were all over the place, including two Oehlers... which didn't match by ~100 fps.

And the errors were not consistent - one would be higher on one string and lower on the very next string. - one would have a 25 fps difference on one string, and 45 fps difference on the next.

I called Ken Ohler and asked if there was a way to check calibration, and after a 45 minute discussion, we agreed that there was no way to check anything, without a humongous amount of laboratory equipment.


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that confirms what i thought.

it seems that some days my chrono is all over the place, or will give me an obviously errant reading once in a while. i just toss out the anomalies, and fire an extra round.

i have wanted to run the same load through different chronographs to see what happens. sounds like i dont need to, but rather just accept the chonograph as providing information that means more for its relation to other readings and not as an instrument with absolute data.
 
Accuracy trumps speed anyday for me, my fastest chrono speeds are sometimes over 1" groups, so slower accurate groups equal 1 shot kills.
 
We shot through my Oehler and a Chrony a while back, they were pretty close on several strings. The $100 Chrony surprised me.

A bright sunny day seems to help.

Ken Oehler is a neighbor.
 
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I also have several loads that shoot the best at maximum load, actually best groups at pressures that would give short brass life. So I back down just a tad.
 
I tested a few .223 loads usin a cheap Chrony F1. Had a 33fps spread with one load and a 190fps spread with another. Both loads shoot 1/2-3/4moa. Out to 400yds. As far as chrony accuracy, i bet they vary from one to another. I shot my .45acp thru it and it read around 1,500fps 5 times in a row. So i knew something was up. Tried again and it read 850fps wich is more realistic.
 
Mine seems to be fairly consistent as long as I monitor conditions. As was stated earlier a sunny day helps. Also beware of shadows, like from the roof over a firing line. That one stumped me for a while many years ago. The shadow moved over my chrony right in the middle of a test session and had me scratching my head for a while.
 
I've had 4 different ones all of them were slow. The newest and the slowest one yet I've shot twice the next time will be on purpose.
 
I know something is screwy if my chrono reads high. If it does read high it's usually about 200 fps, my brother has the same one and they read different from each other, just use what you have, and stick with it, I dial most of my shots so I hope for the best possible reading I can get.
 


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