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Old December 6, 2012, 02:53 AM   #1
chris in va
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Got a chronograph, now what?

ProChrono came in today. Any tips on how to use it besides what the manual says?
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Old December 6, 2012, 03:02 AM   #2
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just don't shoot it
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Old December 6, 2012, 03:03 AM   #3
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Shoot it, to get the dirty deed over with.

Then, buy another one and start testing your loads.
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Old December 6, 2012, 06:00 AM   #4
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Not sure what all your instructions might say. There are are some forms that you can make copies of for your load data when using a chrony that records your shot string info and provides the formulas to figure out your extreme spread, average and standard deviations as well as your stored energy for a given load. These or at least a log book of some sort to record your data in are a must in your load developement . Buy a spare battery right away as if the battery gets weak it will start to get cranky and you will start chasing your tail trying to figure out whats going on. You will get false readings, skipped readings, error messages and so on. When in doubt change the battery. Dont set your chrony up in the shade. It needs good light for the defusers ( sky screens ) to work properly. Turn the thing off between even brief shooting sessions again to keep that battery strong. Look where your barrel is pointing in relation to the sky screens and not what you see in your scope or you may just get the dirty deed done and shoot your chrony . Cant think of anything else except to carry a couple of pens with your chrony. Memory isnt all its cracked up to be.
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Old December 6, 2012, 07:04 AM   #5
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As soon as necessary/practical, replace the issue Alkaline 9v battery with a Lithium one.
That will make all the difference in stable/accurate reading once the temperatures drop this Winter.

(Valuable lesson from UncleNick on my Oehler35 -- never to be forgotten)
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Old December 6, 2012, 07:57 PM   #6
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Excellent suggestion. I need to do that as this trigged a yes its the orignal battery light.

As for the use, you have to play with it.

Start with the basics and do one shot at a time to get a feel for it.

If not a logger type then you need to log each shot. If its a logger than you can shoot strings.

Those will give you the velocity of each shot, you can see what the average was and the standard and extreme deviations. That tells you a lot about ho consistent your loads are.

If the load goes no linear (velocity does not increase per the listed increases) then its your indicator that you have gone too far pressure wise.

Your initial velocity may not match what the books says, but if the book says you increase the power by 1 gr and you get a 50 FPS increase, your load should match that pretty closely (average).
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Old December 6, 2012, 08:17 PM   #7
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Two suggestions:

A common error is to have the unit too close to the muzzle. I never use less than 10 feet with handguns or 15 feet with rifles. The instructions may say closer is fine, but I think that's somewhat light condition dependent. Better just to set it back a bit more from the outset.

Take a laser bore sighter to the range with you. Set the gun up with the bolt open, slide back, cylinder open, falling block down, or whatever your gun has as a safe condition. Set the gun up on bags so the sights are aligned with the target. Put the bore sighter in and turn it on. Use the palm of your hand to find the laser and set the stand up so the laser hits your palm in the center of both screen areas.

Go back to the bench and check that the sights are still on the target before you touch anything. If not, adjust them and go back out to check the chronograph position. When it is right, REMOVE THE BORE SIGHTER (can make a mess of both your gun and bore sighter if you forget to).

That last setup procedure answers the question, "how far should my sights be above center in the chronograph screen area?" Using this method you know that when the sights are on the target the bullet will transit the middle of the screen. This minimizes your chance of shooting the unit.

What to do with it? A good beginning project is to go back and get baseline velocities for all your established good loads. Simultaneously you can verify they are still grouping well and don't need to be tweaked further. Having that average (mean) velocity number, if you run out of old component stock and have to change either the primer or powder lot number, you can quickly adjust the load to get the new lots to match the velocity of the old. This assumes the brands and types of component are the same and only the lot number has changed. Matching velocity with a different powder, primer, bullet, or case will not automatically get you a match to peak pressure or barrel time, as these are affected by various characteristic differences of the components, especially of the powder, and are not determined by velocity alone.
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Old December 6, 2012, 08:22 PM   #8
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Record velocities and calculate the standard deviation of a string using only a pencil and scrap of paper. And as was said before, shoot a hole in it. They really are nice for working up a load. Bear in mind if you are beating factory you are probably over SAMMI.
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Old December 6, 2012, 08:36 PM   #9
blackhawk8
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Take your time setting it up Chris, dont do like I did. got big hurry and pulled trigger and the screen went blank, Yep big hole right down the middle of it.
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Old December 7, 2012, 02:02 AM   #10
chris in va
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Thanks guys, good advice.

Took it out today and was quite shocked with some of my loads.

My cast 9mm 125's were around 800. The gun functions fine with them but surprised they were so slow.

45acp 230's are about 700. Again, less than I expected.

The real shocker was the 155gr x39's out of my CZ. 1500 on average, way low. Interestingly they have the same recoil as factory Wolf 123's at about 2300. Weird.

My 223's in my Sport were...2200fps. Yikes. Gonna try a different powder.

No surprise are my Garand loads. 2700, very little deviation. Perfect.

CCI 22's through my Kadet are 1050. The box says about 1300 but I'm sure it's with a rifle.

I was very mindful of bore axis when I set up the unit, especially using the AR. I looked down the side of the barrel before firing.

Last edited by chris in va; December 7, 2012 at 02:09 AM.
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Old December 7, 2012, 03:23 AM   #11
oldandslow
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Chris, 12/7/12

Being almost a chronograph "Ace" (I've shot 3, two more to go to get "ace" status) I can tell you what not to do.

With my first Chronograpy, a Pact that I tried to make work for five years, I finally (intentionally) put three 9mm rounds through the skyscreens. It worked just as well afterward as it did before. It would only show accurate data early in the morning or late in the evening when there was no sunlight. Sometimes heavy cloud cover would work. I tried all the usual things to make it work but no luck.

The second- a ShootingChrony. Worked quite well until I shot the LED screen with a shotgun wad. I was plenty high enough for the 12 gauge slug to clear the skyscreens but I forgot all about the wad. Now I put a small section of 2 X 4 in frone of the skyscreen before testing shotgun loads. You don't need this precaution with rifles or pistols.

The third- the above ShootingChrony after it was repaired by the factory. I was zeroing a scoped rifle and low and behold I was not holding high enough when viewing through the scope. The bullet just creased the metal above the skyscreens but it still works well. That shot really messed up my group however.

So in summary- shoot high, watch the shotgun wads and don't be surprised if your loads chrono below what you thought they would be. Every reloader needs a chrono to shoot to their full potential.

Merry Christmas- oldandslow
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Old December 7, 2012, 04:43 AM   #12
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Here I am at the range with my second Pro Chrono.

The first one, I shot with a handgun, it only took ~ 10 shots.
This one has lasted for years on a diet of rifle shots.
I shot two shooting Chornys the same way before that.
I now only shoot a handgun over it, after practicing with that handgun. The group has got to be small enough for the chrono to be safe.

The chonograph is screwed to the top of a camera tripod. There is 1/4-20 thread screw on the top of the tripod and a 1/4-20 female nut on the bottom of the chrono.

The chono is way out there, so it will not trip on gas.
It is carefully lined up between the target and the gun when the range is cold. I must go get it to take it home when the range is cold, too, so plan ahead.
I aim the rifle to have the bullet go right over top of the chrono, about 4" higher than the top of the chrono.
There are a pair of binoculars to read the Chrono display, it is so far away. I I have paper and pen to write down the data.

I do not use the pole sticking up out of the chrono, nor the opaque diffusers.



I useually get away with that, but at 3,000 feet on a dry sunny day, a 3,000 fps 25 cal bullet will not make much of a shadow and I will wish I had those diffusers. On a cloudy day, no problem.
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Old December 8, 2012, 01:35 AM   #13
chris in va
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Wow, that is far away. I might move mine back a bit for rifle, starting to wonder if the muzzle blast was causing a low reading. Of course we're getting four days of rain after being in a drought, go figure.
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Old December 8, 2012, 02:59 AM   #14
steveno
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muzzle blast will give you erratic readings that vary by several hundred or more fps and usually quite high
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Old December 8, 2012, 07:59 AM   #15
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Muzzle blast can also give low readings. That occurs when the gas trips the front screen (before the bullet gets there) but not the back screen (so the timer has to wait for the bullet to get there), making it seem like the bullet was between the screens for a longer period of time than it actually was there.

High readings occur when the muzzle blast is strong enough and the screens close enough that both trip on the gas and never see the bullet, because close to the muzzle, the gas is travelling faster than the bullet. Really severe muzzle blast apparently can actually increase the bullet velocity a little bit AFTER the bullet has left the barrel, as the gas blows by the bullet. (But, the turbulence of that process can also deteriorate accuracy.)

SO, if you start-out setting-up your chronograph much too close to your muzzle, and then move it back in stages, you may see the muzzle velocity reading be way too high first, then become way too low, then finally be correct when you get far enough away.

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Old December 8, 2012, 08:44 AM   #16
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Oldandslow--Ha Ha . I am tied with you. I also have 2 on my wall of shame

Best advice i can give you-If you set up to shoot at 300 yard targets,DON"T
take your first shot at 200 yards.

They are pretty much a no brainer to use. Set them up 10 feet away from your muzzel. The shades,,You don't need them unless you are in the sunshine.

JUst check and recheck your bullet path. I found out the things last longer when the bullet goes over the top of the croney ha ha
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Old December 8, 2012, 11:44 AM   #17
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Most, maybe all, chronos these days calculate standard deviation (SD) for you, but other than knowing that (generally) a small SD is better than a large SD, very few handloaders know what use can be made of that information. Here's one practical application for hunters or anyone else who's interested in seeing how a particular range of velocities translates into vertical stringing due to the difference in velocity alone.

If the distribution of your velocities is "normal" in a statistical sense, i.e., follows a bell-shaped curve (and all of the velocity data that I've worked with is pretty close to normal), then for all of the possible times you shoot that load/rifle combination, about two-thirds of the velocities will be within +/- 1 SD of the mean, 95% will be within +/- 2 SD, and 99% will be within +/-3 SD. Knowing that, you can take your mean (average) velocity, subtract 2 SDs, add 2 SDs, and know that 95% of the time (probably good enough for most of us, but use 3 SD if you like) the velocity of your next shot - or your first shot at game - will be within that range. Knowing that, you can take any of the commonly available trajectory tables/calculators and plug those numbers in to see if the resulting vertical spread is going to be acceptable for the game and expected distances you'll be hunting. If so, you're done, if not it's back to the reloading bench, or perhaps back to the LGS to try some other factory load.
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Last edited by Unclenick; December 8, 2012 at 05:13 PM. Reason: fixed math typo
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Old December 8, 2012, 10:02 PM   #18
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Do as they suggest in the instructions and take some red electrical tape (or any other color) and make a loop on the rods about 4-5 inches above the Chrony, and then you'll have a spot to aim between so you don't hit the chrony.

On some bright days I have found it helps to tape a big piece of translucent plastic over the top of the sky shields to keep really bright sunlight off the eyes. Try one of those 2 x 4 foot pieces of plastic sold for recessed light fixtures.
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Old December 9, 2012, 06:04 AM   #19
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Chris you may want to experiment a little more before adjusting your loads. I would definetly repeat the test on the 3 loads you believe are low. Make sure you are far enough away and experiment w the diffusers and time of day (sun light) as mentioned in other posts.
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Old December 9, 2012, 01:41 PM   #20
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If your chrony came with aluminum screen support rods replace them with wooden dowel rods. That way if you hit one its not a big deal.

Ask me how I know.
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Old December 9, 2012, 02:38 PM   #21
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I attached a small chain to mine, that was 15 feet long that way I had the same distance from muzzle to measurement each time.
I found that some people cant read a tape measure!

Found some key chain that was 15 feet lone at Home depot so I used it.
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Old December 10, 2012, 10:04 AM   #22
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Buy a brick, at least 500 rounds of fairly good 22 ammo. It doesn't need to be expensive target ammo, just something that the velocity will be pretty consistent on. On each range trip fire 5 rounds or so of the 22 ammo and record the average velocity. Use the same 22 rifle for this each time BTW.

Even with expensive chronographs the velocities they record will vary quite a bit because of differences in the sun's angle, and intensity. Temperature and other atmospheric conditions can effect velocity as well.

If you get readings with the 22's that are higher or lower than normal then you should expect to get the same with the centerfire ammo you are testing that day. Sometimes even at different times on the same day as temperature and the suns angle changes. If you are using the chronograph for more than an hour I'd recheck with the 22's occasionally.

If you get normal speeds with the 22's but your centerfire ammo is shooting faster than expected then you know the load may be a little too hot. If you are getting faster than normal speeds with both the 22's and your centerfire ammo it may just be that your chronograph is recording speeds a little fast in those conditions. This helps give you a better idea as to whether your loads need tweaking or not.
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Old December 10, 2012, 06:36 PM   #23
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JMR40-You bring up some valid points. I think what most likly is happening is as you state-The bullet is going faster,not because the crohny is faulty but because out side temp is causing the bullet to go faster. The same load shot on a 40 degree day will shoot hotter and faster on a 90 degree day. The chrony is just simply showing you the difference temp can make. I know some bench shooters that will set there ammo in the sun shine before a match to heat them up and i also know some that will keep them in the shade.
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Old December 10, 2012, 11:50 PM   #24
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I started with a BB rifle with mine ,then a 22 , I had to ease my nerves into it !!

More gooder readings at 15-20 feet, muzzle blast made me pull all my hair out until I figured it out.

On a real brite day I use a translucent 5 gal bucket to difuse the lite.

Also I use skewers marked hi enuff for a scope to line up with .

The skewers break when hit the steel rods jerked mine of the table when hit ! & NO there were`nt a hole in the chrony !!!


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