Home Forums Reloading Big Game Rifles Chronographs???

I bought an F-1 Shooting Chrony and the speeds seem to fluctuate WAY TOO MUCH. What could be the problem?

The wind?? ?? ??

Run a 22LR over the screens and see if the velocity settles down.

Lighting can really mess with a chrony. "High Sun" will screw them up bad. Shoot some factory loads of some kind and check it out. If it's handloads giving wild velocity swings...you got a lot of figgerin' out to do, gun, loads, chrony, etc.

+1 on the .22LR. esp match loads of known velocity. 99% of the time it turns out to be a lighting issue. some more info on your part may help....

It was late afternoon around 5 PM. I had the chrony set up the way the instructions said. I had in on a tripod about 8 feet away from the bench. Sometimes I would get 2671 fps and the next shot will be 1054 fps. Should I move the chrony back further?

I would have the chrony at least 10' from the muzzle of the weapon you are firing.
On some of the bigger calibers with considerable muzzle blast, I will go all the way out to 12-15' with my Oehler 35.

I don't think so. the biggest issues I've had were with the sun at an angle -- early morning and late afternoon are the worst. The best (most accurate/consistent) readings for me come with the sun overhead (using the sunscreens) or before the sun comes up.

Here, shooting starts at "daylight at the range" = light enough to see. I try to get all my chrony stuff done before the sun comes up over the mountain -- otherwise readings are haywire until about 11 am.

I just got off the phone with PACT regarding problems with my Model 1. They suggested the following:

Muzzle 5-10' from screens
Wires lying on the ground, not touching each other
Readout box not on bench, to avoid muzzle blast distortion
Overcast sky preferred
No exposed insulation on wires leading from screens
Brand new battery, also heard not to leave battery in unit between uses

Mr. WinModel70:
You�ve received some good advice so far, sounds like possibly a light issue to me as well.
I�d have to say about +20 to Tim�s suggestion to move it out some. When you burn 75-80 grains of powder, 15� is plenty close��.I put an extra �� plexiglass shield on my LCD readout screen on my old Chrony after I um, �damaged� it with one of the powder burners.
The .22 suggestion and new batteries good things to try as well.
Chronos are a good thing for any reloader, so good luck with it.
Dwayne

Update:

Tried all the above suggestions with my PACT Model 1, and low-and-behold, it works! And this was with a .177 RWS air rifle. Now tomorrow, who knows.......

I have a "shooting chrony beta model" and I used to have the same problem. The sun light had to be just perfect or the readings were all over the place, mostly way high. One year I read an article on chronographs by John Barseness and his tip to fix that was to put a strip of cello tape over each photo cell. I have been doing this since the article came out(4 yrs?) and have never had the problem again no matter what the light conditions are. I havent even used the diffussers since I started doing this. Im not sure if this would apply to your model or not.

This has been my experience too. I've noted that although measures of variation (i.e., ES,SD) are greater when the sun is at an angle, the average velocities under all conditions are very close if not identical.

I've got a Beta Master Shooting Chrony it's very easy to get good readings from, shoot into the middle of the area defined by the screens and supports and have the light overhead as much as possible, I always use the screens too. No problems unless due to recoil or some such I start to get off to one side.

I cured all my chrony problems. Sold it and got an Oehler. Problem solved.

Based on my experiences the most likely culprit is sun angle. Early and late in the day with the low sun angle causes issues in accurate velocities. I base this on having used an Ohler 35 and more recently a Millenium and my friend's Pact. We believe we have solved the low sun angle issue at least for our conditions.

The range faces east,early in the morning, we cannot get readings from the Ohler or Pact, the Millenium reads but is as low as 150 fps. We rig up a target stand with some cardboard hanging off the side. The carboard is cut and positioned so it shadows the sensors but allows the sun to hit the skyscreens. So far is has works on all three chronographs. It may not work for you but it is worth a try.

I agree on using a 22 RF or a known load to verify that the chrono is accurate.

I too have found the lighting to play with my chrono`s so I`ve been running a "proof" screen lately. I wanted to see if the readings are off or are "true" even though the screens are haveing trouble picking up the bullet. The units seem to be as accurate when lighting is to the point they drop a shot now and then, as it is when the light is optimum. Although the individual shots may show some spread in velocity that appears to be wide, the reality is they are only a percent or so apart and are very close over all.
Here are some the readings I got yesterday between 1:30 pm and ~ 5 pm. The rifle was a 708 with 2 different bullet wgts and this was during load work up.
Pact-------Shooting Chroney
2905 fps---2891fps
2960 fps---2954 fps
2737 fps---2781 fps
2783 fps---2774 fps
So much for the one is more accurate line. I try to keep the screens shaded but in the late afternoon the screens are pointing at the sun as the range runs east/west.

You havn't shot it yet! That cures any fluctuations.

AGW

People seem to have this particular problem fairly often, and it's puzzling.

I've had two Chronys... first died of a 9mm round. Both were very consistent and stable. I do my chronographing between about 10:00 a.m. and 3:30 p.m., 10-15 from the muzzle, with sunscreens, without the extension rods, and only on days where there is enough sunlight that I can see the shadow of the tripod. I practically never have problems.

There seems to be a very different subgroup of Chronys out there that don't behave nearly so well.

I've talked with the people at Chrony, and it is painfully apparent that they are producing a design that they bought, and know nothing about. I wouldn't expect any meaningful technical help from them, and I wouldn't expect them to detect a condition where a large part of their production was defective.

So, when my present Chrony finally steps in the path of a passing projectile, I'm thinking CED Millenium. Til then, I have what I have.