Funky Chronograph readings

[7br]

Ok, I took my nephew's shooting chrony to the range this evening. When I shot at 6 feet, readings where mid 2500 fps. At 10 feet, reading was pushing 2800. I also noticed that when I switched targets, velocities jumped about 75fps.

My nephew thinks the bullet can still speed up when it leaves the barrel. I don't think it can. That leaves me thinking I am getting bad readings.

Any ideas which are the correct readings?

[theperfessor]

Bullet can't speed up. Sounds like either your screens are set up wrong or you've got a dying battery. I'd check the battery first.

What distance to the screen does the manufacturer recommend?

[7br]

Unfortunately, ron got it used I don't have the instructions. I did clip one of the wires that hold hold the screen last time and kind of messed up the defusers.

[Gelandangan]

Check the ambient lighting.

Chronometers works off light,
they are very sensitive to the point that AC powered light bulb would trigger them to give false reading.
Often times, shadows off leaves would make them give you strange readings.

[Larry Gibson]

6 feet is to close. Everytime you set up the Chrony set it at the same distance to get consistency in the readings. I'd suggest that 10 feet is the minimum. Also both screens should either be shaded or in the sun. I don't own a chrony but many of those that do seem to have this problem, might check the batteries as suggested.

Larry Gibson

[runfiverun]

8-10 feet is correct.
i measure from the bench in the scientific method of my arms width plus one arm length.
just kidding. i use a string i leave tied to the front screen,it help with wind too.
anyways if your too close muzzle pressure will move the screens.

[JIMinPHX]

They can be affected by heavy muzzle blast, florescent lights, low light, low battery, specks of lube that come off the boolit, and detached gas checks. Maybe other stuff too.

[montana_charlie]

Unfortunately, ron got it used I don't have the instructions.
The manual is available at http://www.shootingchrony.com/
Just pick the one that matches your machine.
CM

[Lee]

bad clouds also, although that seems like BS.
Otherwise for a small caliber handloade booloit I would look if loading practices could perhaps cause a 300 fps difference in velocity?????

[wistlepig1]

I had the same problem and cleaned the lens with Q-TIP, Prob gone.
+ any or all the above!

[Cherokee]

All good comments. I use 12 feet.

[jsizemore]

My instructions say to set-up 5-15 feet. I've always took that to mean air rifle at 5 feet 300 ultra mag at 15 feet, and all others fall in between depending on velocity and powder charge.

I've gotten funky readings when my light source was low in the sky like early or late in the day or winter time shooting. Since the chronograph operates off the shadow produced by the passing bullet/boolit, a switch to different targets might put your outside the screen in relation to the light source.

In the winter or early/late shooting I've set up clip-on temporary lights overhead in my shed with incandescent bulbs and got good readings. Florescent lights will get you nothing. Good Luck

[Mk42gunner]

Not to be a smart alec, but did you have it fully unfolded? I found that to be a problem when I first bought mine used.

Mine is old enough to have came with the pressed fiber sighting guides. It still works as long as the battery is good. I do try to fire a shot over it with a .22 first; just to make sure it is reading somewhat close to reality. I also keep several new 9-volt batteries in the case with it.

Robert

[Mal Paso]

BLT and I were 2 lanes (with walls) from each other today, both of us with Shooting Chronys and the concussion from my gun was giving him error messages. For a while we were both getting nutty readings at the same time. For a while I was getting better than 2200 fps out of my 4" Redhawk. I swapped batteries, changed tilt, cleaned the lenses, Bottom Line, They are made Too Cheap.

Anyone have experience with a better one?

[lwknight]

Your bullets were probably drafting the other lanes' bullets and picking up speed LOL.
It sounded good for a cheap shot anyway.

[JIMinPHX]

Anyone have experience with a better one?

My chrony has been working great for over 20 years. I have 2 binders full of documented targets that have velocities logged on them from the same old F-1 Shooting Chrony. I just recently replaced the sky screens because they were starting to crack & some were turning yellow from age.

The only times that I got strange readings were when the unit was too close to the muzzle, I had large muzzle flash, there was poor light, the battery was low, I missed a sensor, or multiple objects (i.e. separated gas check or sabot) went over the sensors. I've been real happy with my chrony. I think it was about $65 back when I got it in the late '80s or so. I think that it was a great investment.

[Gee_Wizz01]

I have a Chrony Beta Master, that I bought about 10 years ago. I haven't had any problems that were the Chrony's fault. One time I found my velocities were higher than I thought, and found a piece of debris on the tripod head which prevented the chrony from unfolding completely. They don't like fading light and will give errors if the ambient light is too low. Friday I was shooting my .45's with the chrony at 8'. My loads were hot and I was getting about 1200 fps. I shoot one round that registered 2500 fps. When I checked, I had stepped forward, and I was only 6' from the screens. I stepped back and my velocities went back to normal. When I check the chrony, I had a couple of spots of splattered lube on the diffusers and front of the chrony. I am happy with my chrony, when I purchased it, itwas the only chronograph in my price range.

G

[405]

That bullet speeding up is the "JATO" effect. A small quantity of powder is stuck in the base of the bullet and ignites as it leaves the muzzle giving the bullet extra boost. Of course the effect is greater with hollow based bullets. :mrgreen:

Seriously, I use an old F1 and never have had the problems you describe. Either I get a valid reading or error message. As has been posted many possibities. I know that direct sunlight on either or both of the sensors will mess up readings. Cast bullet shooting blows lots of junk out the muzzle. All that junk passing over the sensors will mess up the readings. I use 15 ft from muzzle as a standard for all shooting and use a couple of index cards taped to the side of the unit to shade the sensors from direct low angle sunlight, if needed. Also, bugs flying around the sensors can foul things up.

[7br]

I guess I should fess up and let you know I was shooting J-word bullets when I got the error. I am fairly certain the first readings were to close to the muzzle. Will have to shoot another time to verify though. t

[Rocky Raab]

Quality isn't free, as we all know. To get better, you have to pay more. While Shooting Chrony machines are fine for some reloaders, they do have drawbacks. Not to put too fine a point on it, but cheap is cheap.

When you need a better machine, look at Pro-Tach, CED, PACT or the ultimate non-professional system, the Oehler (now available again in very limited numbers).

[Mal Paso]

Thanks! I really appreciate your input! I do think Shooting Chrony gives you A Lot for the money. The Multimeter I use for work was $300+. I don't know how they make the Shooting Chrony for the price. That said we spend a lot of time and ammo working around lighting issues, etc and I think both of us would spend a little more time/money for a better machine. I'm going to try to repackage BLT's Beta and experiment with the Sky Screens. BLT is compiling his own load books based on real guns and is looking for a better machine. I searched archives last night and maybe didn't go back far enough but I've gotta think some of you have been "there" before. I will post whatever I find.

BTW I had the Chrony far enough away that the cable was just touching the ground in the middle.

[405]

I guess I should fess up and let you know I was shooting J-word bullets when I got the error. I am fairly certain the first readings were to close to the muzzle. Will have to shoot another time to verify though. t

Just taking a quess here, but gas velocity near the muzzle, especially with hi-vel Jbullet loads, can be a bunch higher than actual bullet velocity. Some chance I guess of ghost readings of the gas cloud as it passes over the sensors. Also, if pretty close to the muzzle the powder gas ejecta along with the compression wave could really rattle the unit right at the time it needs to be still and stable for accurate readings.

[Yosemite Sam]

I have found that shot-to-shot variation decreases with my shooting chrony when I make sure the bullet passes directly over the photocells. When I just put them under the diffusers and between the rods, variation increases. Can't make any sense out of it, but that's what I have found. Always put the chrony ~15 ft from the muzzle.

[firefly1957]

I recently had my older Chrony out to do some load development with my 45 acp.
And had a terrible time getting good readings I lost the manual so I went to problem shooting on there web sight and found they need alkaline battery. I was using a heavy duty battery and it did not work right new alkaline battery worked fine.

Did have a problem timing Corebon bullets out of 1911 but not out of Sig p-245?
All loads timed well in all three of my 45 acp's but my carry ammo Corebon 165gr +P it time 1180 to 1200f/s @ 20 feet out of 3 3/4" P-245 but gave me mostly misreadings out of 5" Colt 1911 with a round @ 1427f/s and one @ 1425f/s which seems a bit high.

Another note when firing things with a lot of muzzle flash I do move the Chrony to about 30 feet like a 10" contender in 30-30 with a charge of RE-7 behind a 110 gr bullet any closer and I get <error> I am assuming the flash is the problem.