Chronograph Problems!

scsims

I beleive that my chronograph is not reporting correctly. Because everything that I shot through it is lower than the load data. Most load data I look at is using a 24" barrel and mine is a 26" and all of my loads are about 150 to 200 fps slower than they have for the shorter barrel. Could it be that I'm shooting too low or high above the chronograh or that it is too close or too far from me. Any ideas guys?

Has anyone else had problems with their chronographs not working correctly on sunny cloudless days?

leeblackman

Well there are other factors that will also effect velocity, such as air pressure, and altitude.

Kdub

Usually when a chrono isn't responding correctly, the readings are really gross. Several questions:

Are you shooting factory ammo? If so, you should be reading somewhere near the ammo mfg's published charts.

If handloads, these can vary from the velocities published by the reloading manual due to differences in chambers, lot #'s of powder, type of primers, type of cases and type of bullets. Weather conditions and altitude will also affect the readings.

Hopefully, your chrono will have 2' of spacing between sensors. The Chrony's only have 1', but usually do a decent job of recording, depending on light conditions. The sun screens should be used on bright, sunny days. The sensors are picking up the shadow of the bullet as it passes over them. If there is a bright reflection off the bullet as it goes past, you can get screwy readings. Same if you get direct sunlight into the sensor. Sometimes I'll attach "side blinders" out of cardboard to the sun screen holders on the side where the sun is strongest to block out extraneous light.

You may be too close and getting some muzzleblast past the sensor along with the bullet, or you may be too far back. The standard standoff distance should be somewhere between 10' to 15' from the muzzle. I set mine at 13' to 15' and normally have no problems. Most reloading programs have the means to factor these distances and determine true muzzle velocity. It only amounts to a very few fps anyway, so no need to worry much about.

One other very remote problem is the nearness of microwave or other communications towers. We have several perched on a hill near our gun range and at times there is interference with these.

Hope this gives you some angles to consider.

Keep off the Ridgeline

jrip

There may be nothing wrong with the Chrongraph at all. In my experience, it is not uncommon to see that much variation from published data to actual results, more so with reloading data, less so with Factory load data.

No only can environmental factors cause changees in velocity, but so can physical charcteristics of each gun. Such things as barrel smoothness, actual bore size, chamber size, all create differences. Also, some of the published ballistics are taken from pressure barrels, not actual firearms.
All these things can cause discrepancies from published ballistics to actual ballistics.

aglore

You may also have a slow barrel.

AlleninAlaska
Delta Firearms & Supplies
http://canadianfirearmsexchange.com

aglore@gci.net

gunnut505

I think the answer is in your post.
"cloudless, sunny days" means you need a light diffuser over the sensors.
You may also get differing velocities using the same load data from 2-3 different sources; bullet manuals are typically faster than the powder manuals for some reason.
I use a PACT model 1 without skyscreens(my 300 blew them to bits) for checking my loads, but I make sure to shade the sensors, or at least set up a diffuser(tupperware lid from bread holder works real well) clamped to one of the tripod legs so the sensors get a good look at the bullets.
I've never had troubles unless the battery's going dead.

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