Shooting Chrony Problem

bignz · May 7, 2010, 09:16 PM

I was hoping to find some help with my new Shooting Chrony.

I was using it for the first time today at an indoor range with the light fixture on top. I was testing a series of 45acp loads out of my 1911. I had a series of rounds manufactured ranging from 4.0gr of Bullseye up through 4.9gr - all with 200gr LSWC rounds. I was anticipating around 750fps - 850fps based roughly on load data.

The first few shots of 4.0gr. registered in the 1470fps range. I figured this was due to the chrony only being 7 feet away and picking up muzzle blast. I moved it out to 10 feet, same thing, 15 feet, same thing, then I moved it as far as the telephone cord that holds the display would go (maybe 20 feet) and I was still up in the 1400fps range.

What's going on here?

dfe2240 · May 7, 2010, 09:27 PM

If there are fluorescent lights at the range, that might be the problem. Fluorescent bulbs flicker and that skew readings. The lights on the chrony should eliminate the problem, but should and does are sometimes very different. Try a few tests outdoors under natural light and see if the reading change. If they don't the unit may need to be repaired.

Lost Sheep · May 7, 2010, 10:02 PM

I think dfe2240 probably has it right. If you do suspect the lighting, try this:

Take your diffusers and lights off the Chrony. Use one of the rods like a wand (or, better yet, a rod or dowel about 3' long) and pass it over the sensors as fast as you can. The Chronograph should clock it reliably under incandescent light or in natural lighting on a cloudy day, but may be erratic under flickering lights (flourescents do flicker at 120 cps, each time the AC changes direction).

I did a test a year ago when I bought a used unit, described below. I don't recall the readings, but they were very low as bullets go, but a hand-held 3' wand should be able to go 100 mph (if a baseball pitcher can manage it with a bare hand I can do it with a wand that doubles my extension.).

I took a lightweight rod about 2 or 3 feet long and waved it as fast as I could over my chronograph under incandescent light, which is steady, like sunlight. I got reasonable readings, so concluded the chronograph worked correctly.

What's reasonable?
60 Miles per hour is 88 feet per second
100 mph is 147 ft per second.
speed of sound is 760 mph and 1100 fps (approximately), but you are not going to get that with a hand-held wand. A bullwhip, sure, but getting it right over the sensors is problematic.

I was able to get fairly consistent readings (That is, I got readings almost every time; my ability to wave a wand at consistent velocities is somewhat less than my ability to hit targets consistently. But the velocity did match closely what my kinesthetic sense told me, and I got better as I practiced.)

Bottom line, I did manage to test the function of the Chrony, which is the point. If you get erratic readings, suspect the lights at the range are over-riding your Chrony's lights and interfering with your Chrony's sensors.

Solution? Shoot at an outdoors range under natural (sun) light. Fallback solution? Put an umbrella over your Chrony to block the flourescent lights and use your Chrony's lights to get readings. Bad solution: Switch to a chronograph using the 30 year old technology of actual SCREENS you shoot through. The depend on the bullet making electrical contact with tiny wires in two paper screens. Not always were the old days better. Last solution, Wait until the next wave of technology comes through and we can clock bullets with radar guns.

Good luck.

Lost Sheep

bignz · May 7, 2010, 10:12 PM

Thanks to you both. Excellent idea with the wand - would have never thought of that.

Field · May 8, 2010, 02:29 AM

i shot my chrono on accident one time,

that was a shooting chrony problem right there.

May 7, 2010, 09:16 PM	#1
bignz Senior Member Join Date: February 17, 2009 Location: North Texas Posts: 196	Shooting Chrony Problem I was hoping to find some help with my new Shooting Chrony. I was using it for the first time today at an indoor range with the light fixture on top. I was testing a series of 45acp loads out of my 1911. I had a series of rounds manufactured ranging from 4.0gr of Bullseye up through 4.9gr - all with 200gr LSWC rounds. I was anticipating around 750fps - 850fps based roughly on load data. The first few shots of 4.0gr. registered in the 1470fps range. I figured this was due to the chrony only being 7 feet away and picking up muzzle blast. I moved it out to 10 feet, same thing, 15 feet, same thing, then I moved it as far as the telephone cord that holds the display would go (maybe 20 feet) and I was still up in the 1400fps range. What's going on here?

May 7, 2010, 10:02 PM	#3
Lost Sheep Senior Member Join Date: January 24, 2009 Location: Anchorage Alaska Posts: 3,341	Non-ballistic testing of a chronograph I think dfe2240 probably has it right. If you do suspect the lighting, try this: Take your diffusers and lights off the Chrony. Use one of the rods like a wand (or, better yet, a rod or dowel about 3' long) and pass it over the sensors as fast as you can. The Chronograph should clock it reliably under incandescent light or in natural lighting on a cloudy day, but may be erratic under flickering lights (flourescents do flicker at 120 cps, each time the AC changes direction). I did a test a year ago when I bought a used unit, described below. I don't recall the readings, but they were very low as bullets go, but a hand-held 3' wand should be able to go 100 mph (if a baseball pitcher can manage it with a bare hand I can do it with a wand that doubles my extension.). I took a lightweight rod about 2 or 3 feet long and waved it as fast as I could over my chronograph under incandescent light, which is steady, like sunlight. I got reasonable readings, so concluded the chronograph worked correctly. What's reasonable? 60 Miles per hour is 88 feet per second 100 mph is 147 ft per second. speed of sound is 760 mph and 1100 fps (approximately), but you are not going to get that with a hand-held wand. A bullwhip, sure, but getting it right over the sensors is problematic. I was able to get fairly consistent readings (That is, I got readings almost every time; my ability to wave a wand at consistent velocities is somewhat less than my ability to hit targets consistently. But the velocity did match closely what my kinesthetic sense told me, and I got better as I practiced.) Bottom line, I did manage to test the function of the Chrony, which is the point. If you get erratic readings, suspect the lights at the range are over-riding your Chrony's lights and interfering with your Chrony's sensors. Solution? Shoot at an outdoors range under natural (sun) light. Fallback solution? Put an umbrella over your Chrony to block the flourescent lights and use your Chrony's lights to get readings. Bad solution: Switch to a chronograph using the 30 year old technology of actual SCREENS you shoot through. The depend on the bullet making electrical contact with tiny wires in two paper screens. Not always were the old days better. Last solution, Wait until the next wave of technology comes through and we can clock bullets with radar guns. Good luck. Lost Sheep Last edited by Lost Sheep; May 7, 2010 at 11:04 PM. Reason: Paragraph 1, named the wrong person, bignsz instead of dfe2240, Fixed now.

May 8, 2010, 02:29 AM	#5
Field Senior Member Join Date: July 11, 2009 Posts: 295	i shot my chrono on accident one time, that was a shooting chrony problem right there. __________________ iPSC=A66009 iDPA=A38321 http://www.youtube.com/user/FieldBoy111

May 7, 2010, 09:27 PM	#2
dfe2240 Member Join Date: January 7, 2010 Posts: 56	If there are fluorescent lights at the range, that might be the problem. Fluorescent bulbs flicker and that skew readings. The lights on the chrony should eliminate the problem, but should and does are sometimes very different. Try a few tests outdoors under natural light and see if the reading change. If they don't the unit may need to be repaired.

May 7, 2010, 10:12 PM	#4
bignz Senior Member Join Date: February 17, 2009 Location: North Texas Posts: 196	Thanks to you both. Excellent idea with the wand - would have never thought of that.