Anybody else notice that their Chrony shows less velocity with identical loads as the sun rises higher?

Today, I started shooting at about 9:30 a.m., and my loads all registered 50-75 fps faster in the morning than they did when the sun was overhead. Sky screens were in place the whole time. It's odd, because I started shooting when the temp was in the 40s, and quit when it was in the 70s, yet, the warmer it got, the more my velocities dropped.

Weird.

No, mine doesn't'.

I have owned a Beta Chrony, a ProChrono, an Oehler 35, and CED Millennium II, and a now an Oehler 35P.

I had all kinds of issues with my Chrony not reading properly in varying light conditions. Things like velocities being 75-100 fps off of what they had been during several previous shooting sessions.

The ProChrono worked better than the Chrony. The Millennium II worked well unless the sun was bright and low, shining toward the unit. Both Oehlers were/are nearly flawless. When there is a rare funky reading with the Oehler, it lets you know because of the third skyscreen.

I bought a Chrony when they first discovered that it didn't take several hundred dollars to make a dependable, accurate chrony. I am still using it and I have yet to experience the myriads of problems others have reported.

I have only ever owned and used (for the last 35 odd years) the original model Chrony with the cardboard sighting screens. Although the screens had provision for inserting diffusers for some reason it did not come with them so I cut some out from a thin plastic white ice-cream container lid.

Always using a good quality 9V alkaline battery,'unplugging' it between use (not just switching off), and always using the diffusers no matter what the day, I have always got consistent results from my Chrony.
For pistol and shotgun I set up reasonably close to the muzzle but for rifle where shooting on a range with covered stations I set the Chrony out in the open probably 15 feet or so away from the muzzle.

I have never had cause to suspect the results I get from the Chrony, with known loads e.g. subsonic 22 ammo and others where publications have checked factory ammo velocities I have got expected velocities from this same ammo. Usually I have a fairly good idea when reloading especially with cast bullets what the velocity should be and my Chrony consistently bares this out.

The skyscreens look for a shadow from the bullet passing over and a white diffuser will provide a consistent background for this irrespective of the daylight and the sky pattern (clouds etc) above the chronograph.

If the muzzle is close perhaps GAHUNTER's Chrony is picking up a reading from vapour caused by powder heat in the cool morning which disappears, or the effect disappears, as the day warms.

quote:

Originally posted by GAHUNTER:
Anybody else notice that their Chrony shows less velocity with identical loads as the sun rises higher?

Today, I started shooting at about 9:30 a.m., and my loads all registered 50-75 fps faster in the morning than they did when the sun was overhead. Sky screens were in place the whole time. It's odd, because I started shooting when the temp was in the 40s, and quit when it was in the 70s, yet, the warmer it got, the more my velocities dropped.

Weird.

Is it possible that, as the ambient temperature rose, the actual temperature of your ammo dropped? Say, your ammo was room temp (70 degrees) of your house and fell as your shooting session progressed?

Lost Sheep

All chronographs out in the open can have a time where they can have a niggle or two from some factors or combinations of factors.

You can also try it with out the sky screens on in cloudier conditions. When I use my CED in shade I just use the IR lit screens and it does a good job with that too.

You might be sure that you don't have reflected light and also that the sensors are at the identical distances apart. It doesn't take much to induce a 2% error.

quote:

Originally posted by TexKD:
All chronographs out in the open can have a time where they can have a niggle or two from some factors or combinations of factors.

Haven't seen that with the Oehler. It just works. In the exact conditions where my Millennium II would fail to read, the Oehler gives good readings. My Oehlers also worked where my Chony and ProChrono failed.

Before I bought my first Oehler, I tested my ProChrono against one. We set up the Pro Chrono immediately in front of an Oehler 35P. While individual shots varied by as much as 20 fps between the ProChrono and the Oehler, the average readings were within 5 fps on each other.

A big advantage of the Oehler is the third skyscreen. You get two readings with each shot. They need to be within a certain percentage of each other or the Oehler will flag those readings. While we all know if a velocity is 75 to 100 fps off, it's hard to tell if it is 20 or 30 fps off.

Is that a big deal? Not for most hunting rifles. I bought my first Oehler when I started competing in 1000 yd benchrest. A 20 fps variance would give a vertical dispersion of about 2.5". That can be the difference between winning and losing, so for that game a precise chrono is a must. A true long range (600-1000+ yds) hunting rifle ought to have a precise chrono. Nothing else really needs the level of precision and certainty you get with an Oehler.

The downside to an Oehler is it can be a pain to set up. And it's spendy. It's big and you transport it in a double rifle case. Because of that I sold my first Oehler when I quit competition shooting. I bought the CED Millennium II. I liked the screen, size, and ease of set up on the Millennium II. I didn't like how it was so fussy about light conditions and how it lacked durability. I wound up replacing both skyscreens to try and get it to read in bright, low sun conditions. I also replaced the control unit--one of the receptacles for plugging in the 1/8" connectors had worked loose.

I tried blackening my bullets with a permanent marker. I tried rigging up shade over the sensors. Nothing really worked. So I bought my second Oehler and it works just as well as the first. No failures to read at all in any light condition--though I haven't tried it at night and it's rare when it even flags a velocity. Even though it is bulkier and takes a tad longer to set up, the fact that I never have to fuss with it makes it much more time efficient than all the others I have used.

Your mileage my vary..............

to the OP, yes. My Chrony has never been consistent with changing light.

I just converted over to a Magnaspeed. Initial results are very promising.

But it is a bit fiddly to set it up right initially.