Chronograph Error

[Frank]

Has anyone ever noticed if a chronograph gives a consistently low reading? I always accepted a lower reading with a given gun/load as my gun maybe being different, but now I have tried it on 2 other guns and guess what? They are also too low , by about 150 fps. Now I am wondering if it is the chronograph. Maybe it is out of calibration. It is an older design basic PACT unit.

[DCM]

Do you know anyone in your area with a chrono that you can shoot the exact same gun/load combo over or preferably more?
Like having a bad compass and a good one on a no moon night, which one is right?

I have very rarely found my loads to match published data.
I have an older pact that I have updated the skyscreens to IR on for better reliability.

[Mk42gunner]

I have an ancient shooting chrony that I bought used. I always take a new battery to the range, and shoot a couple of .22s over it to make reasonably sure it is working correctly.

Robert

[Lloyd Smale]

Ive had two chronys and both read high not low and both went back for calibrations and when they came back still read just as high as before. Im talking about 250 fps average on the high side as compared to my buddys ohler. Gave up on them and bought a pact and it reads pretty much dead nuts on with the ohler. buddy that has the ohler just bought on of the cheap rcbs bullet shaped chronos. He bought because he wanted something cheap to leave at his range. Believe it or not that thing is deads nuts on and is even more reliable in giving readings in odd lighting then my pact which cost twice as much. As a matter of fact the other day he told me it was more reliable in differnt light conditions then even his ohler is.

[Frank]

I got some batteries. I remember the PACT guy telling me years ago "Alkaline". I'm going to check with PACT to see what they say. My PACT is OK. You just have to make sure the sunlight is REALLY ON those windows.

Good review by Lloyd about them having different readings and experience with different models.

[W.R.Buchanan]

I found my new chrony is reading about 200fps high. there has got to be some way to calibrate these things other than the factory.

Any ideas other than shooting a known load across them which I don't have.

Randy

[Frank]

W.R. Buchanan:

I found my new chrony is reading about 200fps high. there has got to be some way to calibrate these things other than the factory.

What good are they if they are ever wrong? If it is off 200 fps, it can be off any amount. It has to be exact like a gas pump.

[waksupi]

I found my new chrony is reading about 200fps high. there has got to be some way to calibrate these things other than the factory.

Any ideas other than shooting a known load across them which I don't have.

Randy

What makes you think it is 200 fps high?

[W.R.Buchanan]

It is reading nearly 2800 fps for a load that should be 2600 fps. The load follows the ballistic calcs for drop out to 600 yards based on 2600fps exactly.

Also Chrony's have a rep for being sensitive to lighting conditions. My readings were taken in bright sunlight before I knew about the problems, and these are the very conditions Chrony's don't like..

This prompted me to write to John Barsness who writes for Handloader and every other gun mag. He examined my spent cases, and all of the data I sent and concluded the error was in the Chrony. His does the same thing and I have read a number of reviews saying the same thing.

He was familiar with the characteristics of my load. .308 Win. 45GR of IMR 4895 Rem Primer and 147gr FMJBT bullet, (M80 loading) from a 24 inch barrel and stated velocity should drop 25fps per inch to my 16" barrel. IE 2600fps. The fact that the bullet drop followed the ballistic calcs for that velocity at 5 different distances confirmed the velocity.

This 200 fps discrepency was scaring me as I thought that my loads were really hot, even thought there were no outward pressure signs. However the max load for IMR 4895 with 150gr bullet in Lyman 49 is 46 gr and yeilds 2850 fps from a 24" barrel and is considered safe in all modern firearms. I'm below that so I'm good. I was lookig for 2800fps from a 24" barrel and had extraploated to 2600 from my 16" barrel.

Since the bullet drop at different distances is the final word. I'm good to go and have my Jbullet load nailed. Chrony's readings not withstanding.

However I won't trust it again unless I can verify it's readings. There has got to be some simple way to calibrate this tool in the field.

Looking for something that is not as persnickity. Love an Oehler 35P but at $575 currently that aint gonna happen either.

Randy

[Frank]

I just checked another gun and the PACT is spot on with it. I recorded those velocities 8 years ago. So it is my loads. I was concerned my last two guns were lower. Lower is actually good because it translates to less recoil and a better aim and a hit. With a wide flat nose velocities 900 fps or higher are all that is needed anyway. Since the loads are picked based on either what is most accurate and case extraction (revolver), and the velocity is in both cases at least 1200 fps, what more kililng power do I need? None. I will change the battery on the unit and move on.

Thanks for all the help!

[waksupi]

I asked, because I wondered if you were using jacketed load data for cast, resulting in the difference. John knows his stuff pretty well, so give credence to his opinion. I always enjoyed his visits to the shop. We built a couple rifles each for him and his wife.

It is reading nearly 2800 fps for a load that should be 2600 fps. The load follows the ballistic calcs for drop out to 600 yards based on 2600fps exactly.

Also Chrony's have a rep for being sensitive to lighting conditions. My readings were taken in bright sunlight before I knew about the problems, and these are the very conditions Chrony's don't like..

This prompted me to write to John Barsness who writes for Handloader and every other gun mag. He examined my spent cases, and all of the data I sent and concluded the error was in the Chrony. His does the same thing and I have read a number of reviews saying the same thing.

He was familiar with the characteristics of my load. .308 Win. 45GR of IMR 4895 Rem Primer and 147gr FMJBT bullet, (M80 loading) from a 24 inch barrel and stated velocity should drop 25fps per inch to my 16" barrel. IE 2600fps. The fact that the bullet drop followed the ballistic calcs for that velocity at 5 different distances confirmed the velocity.

This 200 fps discrepency was scaring me as I thought that my loads were really hot, even thought there were no outward pressure signs. However the max load for IMR 4895 with 150gr bullet in Lyman 49 is 46 gr and yeilds 2850 fps from a 24" barrel and is considered safe in all modern firearms. I'm below that so I'm good. I was lookig for 2800fps from a 24" barrel and had extraploated to 2600 from my 16" barrel.

Since the bullet drop at different distances is the final word. I'm good to go and have my Jbullet load nailed. Chrony's readings not withstanding.

However I won't trust it again unless I can verify it's readings. There has got to be some simple way to calibrate this tool in the field.

Looking for something that is not as persnickity. Love an Oehler 35P but at $575 currently that aint gonna happen either.

Randy

[cajun shooter]

I had a RCBS PRO scale and when it went bad I was told to send it to PACT as they are who builds all the electronics for RCBS. Took two send backs before it worked.