Actually, I have two Shooting Chronys that read bullets between 125 and 180 feet too fast, consistantly. This can be a problem when working up loads. For a while I thought "how nice, I'm getting my target velocity with a lot less powder than the book says I should use." Then I figured it out.

Is there a way to regulate them?

Question: If both are off, how do you know?? I'd send them back to the manufacturer and have them calibrated. I know of no way you can do this at home!!

Are you sure that you are shooting exactly perpendicular to the line of sight? those deltas are really about 5% of total velocity, so a 5% error in how straight your shot is going across the sensors, either horizonatal or vertical error will show less time to cross the assumed distance between sensors. Also, once I did not unfold the chrony all the way, adn the same error would have occurred.

another possibility: do you have longer barrel than the test rifles?

And of course, the real question: Is you powder scale calibrated properly? two meters reading the same leads one to accept their accuracy.

If you have two Chrony units, and they are both reading "fast", how do you know? What did you compare them to?

Try shooting some match .22 ammo thru them to proof them. .22 match ammo is usually pretty close to the velocity printed on the box. Understand that the rifle you shoot it thru can make a small difference but it will be consistant. I am also curious as to how you determined that both your Chronies were off?

Jameister
Folding the sensors down will decrease the distance, their by showing higher velocities, yes, becuse you have effectivly placed the sensors closer together.
Shooting at a angle across the sensors will show slower velocities as you have increased the distance (time) the bullet needs to travel between them

Next time I shoot, I will take special pains to make sure that the unit is unfolded all the way. Not that I think this might be the problem, but you can never tell, since I didn't pay close attention to it before.

I too ask as to just how you determined that the chronographs are both reading as high as you claim.If you are making this assumption from loading manuals you would be better off believing the chronograph.Besides the odds of two of them reading the same and both being as far out as you say is not likely.

"Jameister
Folding the sensors down will decrease the distance, their by showing higher velocities, yes, becuse you have effectivly placed the sensors closer together.
Shooting at a angle across the sensors will show slower velocities as you have increased the distance (time) the bullet needs to travel between them"

Stop and think about it.

if the chrony is fully opened, it is max distance between sensors. If it is not, then the time measured will be for a shorter distance and higher readings will result.

now about the shooting at an angle? your right. the bullet will have travelled a longer distance in the time.

I call it a sunday night draw!!

never in doubt, but often wrong.

I know they are wrong because I checked them against some of the "expensive" chrographs the bench guys use at our range. Also, it was pretty obvious when 6 to 10 rifles were shooting hot with a broad spectrum of loads.

I'm going to test loads this afternoon and will take extra care to set up the chrongraph.

Light conditions are what is affecting your Chrony's. Years ago I owned a couple of them and was totally frustrated with the problem. It seemed that diffused light with the sun behind you would be the major problem. I minimized it in a couple of ways, one being to put a "hat" over the Chrony. I made mine out of white plastic. Just cover the entire setup with it. It helped some. Another way a friend helped the same problem was to put a piece of Magic Tape over the reader. The readings were consistent, comparative but inaccurate. Just use it to compare what you are doing that day, not as gospel as to your true velocity.

Have you talked to the folks at Chrony? I believe they would stand behind them if they are off.

I just bought a pact pro to try against a couple chronies..

we'll take 3 chronyies, and the pact pro, put 3 rounds from 4 different guns though each. Wait 10 mins, switch, etc, and see.

My particular chrony is known to be "slow"./.. like 25 fps in the 2000-2600fps range.

jeffe

I'm afraid that I am going to have to pull an Emily Litella, and say "Nevermind".

You see, I went to the range today, and again, the chrony I had set up was reading very fast. So I went to the unit and examined it closely. It seemed that it was not open all the way. So I forced it down. All of a sudden there was a loud "pop" and the unit opened all the way. Seems it was bound by a piece of the case.

The next shot read 242 fps slower than the previous one with the same load, and it showed consistantly lower, right where the manuals said the loads should be.

So, as the late, great Emily Litella once said, "Ne-ver-mind!"