Home Forums Hunting & Shooting Ask The Gunwriters Chronograph issue

I have Pro chrony digital brand chrono that I have owned for about six years or so, I used to do most of my chrographing between nine and eleven in the morning and used to set it up where the rods that hold the diffusers would create a thin shadow over the photo eyes but stopped using that method because due to the suns moving I would have move the chrono every five minutes or so in order to keep the shadow in the same place. I decided to just point the chrono northeast and it worked very well untill a few months ago wen I started to get multiple readings on five shot strings, some times the first and third shot would read the same,some times the second and fourth shot were the same. I tried shooting later in he morning after eleven and that seemed to have cured the problem.

A few weeks ago I was chronographing some loads and the first three loads were reading fairly consistant, the last two shots read about fifty fps faster, I went to check the chronograph and noticed that the shadow created by the difusers was almost touching the photo eyes, usually the shadows are about two inches in front of the photo eyes. I tried an experiment and shot a string with the shadows in front of the photo eyes like I normaly do and then moved the chrono so that the diffusers were shadowing both photo eyes, with the eyes shadowed the average speed was 36 fps less, I was chronographing 223 loads. I called the company and talked to a tech and asked which readings were correct, he was not sure but the readings with the photo eyes shadowed are probably the more correct readngs. He suggested putting a piece of card board or white typing paper over the diffusers that way I have a shadow all the time.

I went out earlier today and was chronographing some rimfire loads using the method with the shadows in front of the photo eyes, I chronographed some rounds using my Winchester model 62a, they were averaging 1182 fps, took my Ruger 10-22 and chronographed the same rounds, the Ruger waa averaging 1208 fps, my 62a has a barrel that is longer than the Ruger and has always produced on the average about 30 fps more speed than the Ruger. I then left the chronograh in the same position and fired some rounds again using the 62a, the rounds were averging about 35 fps faster than the first string, I also noticed that the shadows were almost touching the photo eyes. My question for anyone who is an expert with chronographs is what should I do to if anything to keep the readings consistant. My main concern is that I have some handloads that are near book maximum and if the chronograph is not reading correct some of these loads may be sligtly over max or under, any help is appreciated.

I have had some similar problems with my CED and varying light conditions. Here is a link I found helpful:

http://precisionrifleblog.com/2012/...l-tips-to-increase-accuracy-reliability/

I now use alligator clips to attach a large piece of cardboard to my diffusers, thus creating constant shade. I have checked the results with match grade 22 rimfire ammo. I have also checked the drop at 100yds and 300yds from my 45 Raptor (29" at 300yds) an ran the numbers through a calculator to confirm the velocity. It seems to work.

405wcf

Freddy,

Constructing a larger shade for your Chrony will work, or at least it did with one of the three Chronys I owned before it went completely crazy.

But some light-screen chronographs are more sensitive than others. I've used several that so far haven't shown much variation at all in different light conditions, including my Oehler 35P. The best inexpensive light-screen chronograph I've found in varying light is the ProChrono Pal, which can normally be purchased for $100 or slightly less.

This might not be the answer you were looking for. I also was getting far to wide of a spread in readings from trip to trip and cloudy/ overcast/ sunny...... missing shots, and spitting out half speed readings from my Pro Chrony. Switched to a somewhat pricey MagnetoSpeed bayonet style chrony. Doesn't care if its stone dark or bright sun. Hasn't missed a shot yet, and don't have to wait for down time at the range to set it up. Since it attaches to the muzzle end of the barrel, it does move POI a wee bit tho.

*As close to idiot proof as it can get too. Never shoot it inadvertently, or even by accident.

The Magnetospeed is an excellent chronograph (I also have one of them too), but I do know somebody who shot one.

Perhaps the only flaw in the Magnetospeed is the normal method of operation is connecting it to the muzzle. This affects both point of impact and accuracy, so you can't chronograph and check accurcy and POI at the same time. Some people get around that by making a little stand for the MS, placing it just in front of and under the muzzle.

One of my friends is a gunsmith who shoots and chronographs a LOT, so wants to check accuracy and velocity simultaneously. He build a stand it worked great until one day, when somehow his rifle rest shifted a little and the bullet ticked the "bayonet."

However, he did report that Magnetospeed's customer service is excellent!

My MagnetoSpeed stands alone, not attached to the barrel at all. Love it, works great. No weather issues of any sort.

Thanks for the help.

Freddy, I see that we are fairly close to each other. I shoot just out of Reno.
I've seen quite a few people use their Chronys, and some have pretty good luck, for the most part. All that I've seen, use a northerly orientation. Most shoot about noonish, and only for a couple hours.
They disallow quite a few, in my opinion, but I am not sure WHY they disallow them. I am pretty busy using my own equipment.
With mine, I use the same northerly, but I start at daybreak, which here is about 6:45am, and I continue 'til about 3pm.
After that, as the sun skirts lower, the bright sun starts shining into the skyscreens, and I get erratic readings. It can be unnerving to be shooting a midrange load in a .41 Mag, and get a 4200fps reading!!
If I need to finish a run, before I go home, I put a piece of tape or a sheet of paper between the sun and the screen to put it in shadow.
I don't have much trouble when it's cloudy, but that doesn't happen much this time of year.
I run a load through, a second time at a later date, and come quite close, so I believe the data is correct. I don't run all the loads though again just a one from time to time. I also keep extensive records, so it's not hard to go back and check. Sometimes, I go back 2 or 3 years to dupe a load, and they are quite close, so I believe they are correct.
When I shoot, I keep track of the temperature, and full-value wind velocity, as well as the components of the load. I have Skyscreens, so I want to keep track of the accuracy, too.
The difference of my setup from seemingly everybody else's, is I set my 1st screen at 5' from the muzzle and have a 5' spread, therefore use a 7 1/2 foot instrumental-velocity.
With this close a first-screen, the usual theory is that any of the larger calibers will cause erratic behavior. I was concerned when I first started this setup. I am no longer. I is too consistent.
Some of the calibers I shoot are .300 WinMag, .375/348 Improved, 6.5/06 Imp, and .270 Improved. If those don't affect the readings, nothing will!
I also shoot several handguns...40 S&W, .41 Mag, and .45 ACP.
I've also run .22lr, a few times, rifle and pistol, and mid-range hunting rifle or cast-bullet rifle through with velocities from 500 fps to 2000fps. If the pressure-wave or powder smoke from these loads can't (don't) get around the bullet to start the screen, I don't know that the theory works.
The only thing that I have seen affect my readings is the angle of the sun. I COULD have changed the place I was shooting to a new orientation, but it was more trouble than it was worth. It was time for me to sidle on home.
I use an Oehler M33 that I've had for over 30 years. I wish I could have a 35P as I have to write all my information down with a pen in a binder, and it sure takes up room. I've got six notebooks, just for raw data!
The questions you have seem to be normal variation, though.
You mention that from time to time you get exactly the same reading in a string. Only one time in over 30 years have I EVER gotten all 5 at the same exact speed! There have been innumerable time that 2 or more were the same speed.
Have fun,
Gene

Any number of things could cause a wide extreme-spread in a string of shots. No matter how you weigh/measure your powder, or what kind of primer, or what powder, there MAY be some variation, that will show up in extreme-spread.
50+fps is, in itself, not unusual. I would normally go back and reshoot the load.
I believe that the position of the powder in the case may have a LOT to do with es.
In some experiments with IMR 4895, one of the most popular powders, especially among target (bullseye) shooters, I found extreme differences in velocity due to powder location. I am working to stop the problem, that apparently, few even knew was there, lol.
I prefer to load as full a case as I can.
What rifle are you using?
What, more or less, loads are you using?
Have fun,
Gene

I am going to try something different, I found some light cardboard and painted it flat black, am going to place the pieces of cardboard on the sides of my chrony and then shoot some loads through it, then I will remove the cardboard and shot some loads again and see how much difference there is in the readings. The tech that I talked to told me that readings with the eyes shadowed are probably the more accurate readings whether they read lower or higher, what do you think. I was chronographing 223/556 loads when these issues came up. By the way I live in Fernley.

I would probably try an opaque or off-white cover so that the bullet would appear dark to the skyscreen.

It may have a hard time seeing the bullet against a black background, unless you are using IR screens.

What if I mark the bullets with a black felt pen.

I agree. I don't think a dark background will give the results you want.

White / cream / off white will give a contrast to the bullet.

Good luck.

Jerry

Darker bullets tend to trigger the sensors better.

I use a continuous piece of 2mm thick translucent polyethylene bubble-film, from packaging, with holes to attach over the top of the rods. Light is diffused, and the Chrony seems to work reliably.

I've had some interesting conversations with Ken Oehler over the years about light screens. He himself recommends one solution already mentioned, using a black Magic Marker to darken bullets.

Ken also mentioned that the sky itself can be a factor. At higher elevations the sky appears darker than at lower elevations, providing less contract to bullets. In fact he called the Montana sky "almost black" compared to the sky in Texas, where he's located. But I've still never had any problem with my Oehler 35P "reading" bullets down to 15-grain .17 calibers.

I have mine attached to the barrel, and I get data, and I am done. No silliness.

This:

Constructing a larger shade for your Chrony will work


Is there a link, reference or tips as to how to do this? It is always very bright where I shoot (duh, the desert...).

Regardless, I can't complain about the Prochrony.

Other than shifting POI, and grouping not necessarily being the same as with the naked barrel.

I've seen these effects demonstrated on different, accurate rifles with varmint contour barrels.

Shoot 5 or 10 rounds into the backstop and you have a real good look at numbers like velocity or SD. You can also piss away 10 shots on poor lighting using screens, and get erratic data you can't trust. Magnetospeed is pretty cool, I think it saves time and effort. I would not hang it on a barrel and shoot groups though, but that is not required to get solid chronograph data.