Proper cronograph setup

[cmfi3]

Went out the other day and set up a "pro crono" cronograph for the first time. I mounted it on my spotting scope tripod, placed it 5-8 feet in front of muzzle, adjusted tripod and cronograph and centered it. I then set up my 7mm STW that has a muzzle break and fired off 6-8 rounds. I was getting some crazy numbers, a spread of more than 300 fps. Light was fading, fired a few more rounds and weren't getting any readings at all. What am I doing wrong?
Is the crono to close to the muzzle? is the muzzle blast from the break screwing up the reading? is the low light causing the no reading? What kind of height above the sensors does the bullet need to be traveling? I need some help, I dont want to waist any more rounds on this until I get some proper instruction.

 

[Sendero_Man]

I set mine a minimum of 10 to 12 feet in front of muzzle on a strudy tripod. Center and LEVEL the chornograph. Make sure it is not tilted up or down... turn on and shoot.

I put red tape on mine approx. 8 inches up the rods to center my crosshairs on... this helps alot.

I think you are probably to close and are getting muzzle blast interference as well...

 

[specweldtom]

Ditto; I set the first screen at 21 ft. Yes, as the light fades, the chronograph will start to miss shots, but the 5 to 8 feet may also cause it to miss shots. If it triggers on a shock wave, it'll probably read about 1100 - 1300 fps.

Good shooting, Tom

 

[goodgrouper]

Went out the other day and set up a "pro crono" cronograph for the first time. I mounted it on my spotting scope tripod, placed it 5-8 feet in front of muzzle, adjusted tripod and cronograph and centered it. I then set up my 7mm STW that has a muzzle break and fired off 6-8 rounds. I was getting some crazy numbers, a spread of more than 300 fps. Light was fading, fired a few more rounds and weren't getting any readings at all. What am I doing wrong?
Is the crono to close to the muzzle? is the muzzle blast from the break screwing up the reading? is the low light causing the no reading? What kind of height above the sensors does the bullet need to be traveling? I need some help, I dont want to waist any more rounds on this until I get some proper instruction.

You had minimal light for this "lower end" chrono and it was too close to the muzzle. In the directions, it says to put it at 10 to 12 feet from the muzzle.

Try it again during the middle of the day, preferably on an overcast day, and put it at the right distance. If it is sunny outside, use your diffusers and try not to have the sun at your back or in your face but off to one side.

Low light, fog, dust, and low sun angle are a chrono's worst enemies.

 

[cmfi3]

Thanks for the info guys, I kind of thought I was on the right track, but wanted to make sure. Thanks

GG, are these "lower end" cronographs very accurate?

 

[goodgrouper]

Thanks for the info guys, I kind of thought I was on the right track, but wanted to make sure. Thanks

GG, are these "lower end" cronographs very accurate?

I have an Alpha Shooters Chrony I use for testing bc's and it always reads around 15 to 20 fps more than my Oehler 35 upper end chrono. I have seen some be as much as 50 fps more.

The biggest problem with the lower end chronos is how finicky they get with reading the shots. My Oehler will read 30 minutes past when the Chrony stops working in the evenings and it is more forgiving when light conditions aren't perfect outside.

 

[ScooterDad]

I would also try taking the muzzle brake off or build a wall of sand bags between the muzzle and your crono unit. I use to have the same problem with may digital PACTcrono, and it didnt matter the time of day or the light conditions. I had another member at my range suggest the sand bag wall, since then I havent had any issues.


Scooterdad

 

[TooDogs]

Great opportunity for my first post.

Firstly, congrats on getting a crono. Very useful tool. I've used my CE Pro Crono since 1999. I've not used it in late dusk or early dawn lighting. I have used it on bright sunny, heavy overcast, and indoor shooting range lighting. Worked fine.

Of huge importance is that the crono be mounted on a solid, or, ridged base. A high end sturdy tripod. Or, invest in a folding "saw buck", saw horse. Any means of mounting it solidly will work.

Any instability, the muzzle blast will jostle the crono resulting in the corrupted velocities you are getting. The common low cost tripods are not solid enough in my opinion.

I'll add that I set the crono 12-15 feet ahead of the shooting bench. If you have a BB or pellet air rifle use that to get familiar with the cronos functions.

 

[cmfi3]

Thanks for all the input, went out today and set crony back up. I used the suggestions that were given to me and the crony worked great, thanks guys.

 

[Eaglet]

I would also try taking the muzzle brake off or build a wall of sand bags between the muzzle and your crono unit. I use to have the same problem with may digital PACTcrono, and it didnt matter the time of day or the light conditions. I had another member at my range suggest the sand bag wall, since then I havent had any issues.

Scooterdad​

Interesting, I have a Pact chrono and a ced Millennium. The pact reads my 300 ultra mag without muzzle brake placed at 12" and my 22 rifle but will not read my 300 Sendero Ultra Mag with a muzzle brake. My CED Millennium will read the Sendero at 12 ft. I always try to get a little further if I can.​