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I used a chronograph for the first time yesterday, and my velocities were higher than they should be. Using a 16" barrel with a birdcage flash hider, I was getting an average reading of over 2900 fps with 30.0 hrs of H335 and a 100 gr Barnes TTSX bullet, and out of my 20" barrel with a KVC compensator, the reading averaged 2620 fps shooting Factory Hornady 123 gr SST ammo. I was not worried as neither showed any signs of pressure.
Today, I read the trouble shooting section of the Shooting Chrony website and it said high velocity errors where caused by having the Chrony too close to the muzzle. I had mine at 10 feet as this seemed to be pretty much the universal distance people use.
How far do you place your chronographs from the muzzles of your rifles?
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As far as the cable allows. 15' or so.
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I encountered the same problem. I discovered I wasn't getting the metal box open all the way. It was hardly noticeable but it did make a huge difference. I had put a clip mount that attached to a bi-pod onto the bottom of the chrony. It overlapped the edge and prevented the chrony from opening 180 degrees. After repositioning the tripod mount the readings returned to normal.
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I have been putting mine at 15 feet also. What I discovered is that light conditions effect your readings also. I had read on here about making sure it is all of the way open so I have been doing that but my differences in velocity readings between shooting on a slightly overcast/hazy day in the afternoon and on a bright clear day in the morning have been consistently 60-80 fps slower in the bright early morning lighting. I don't know which one is correct but the readings have been consistent.
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Guys, always put the sky screens on- no matter the conditions outside= helps with being consistant.
15' is the minimal distance for the chrono.. Yes we read the rags claiming they use 10'=== not cool. Most of them are wanna be's- cept for Fortier.
Always, make sure the unit is fully opened before tightening the lower screw,, before installing on the tripod idea- or table.. ===Been there , done that ooops once, twice.
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I have used the sky screens every time I have shot over it, which has only been 3 times so far. I am thinking the variation in average velocities was due to the intesity of the sunlight and possibly the angle. I would just like to know which light conditions provide the most accurate reading so I can do my chronograph shooting at a consistent time of day/conditions and minimize as many variables as I can.
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My experience has been lighting conditions make all the difference. My chrony does not like direct sunlight on the sensors. I seem to have the best results on a bright day with the chrony in the shade. Even with the sun shades in place they only really work if the sun is directly overhead. I have also used a piece of light weight plastic clipped to the factory sun shades for more of a continuous shun shade over the entire chrony with good results.
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That is good to know, thank you. I haven't used it very much yet as I have only had it a short period of time. I am mostly interested in repeatable,accurate results since I am using it to help determine safe loads for my rifle.
