Learning to use my chronograph...

[Gregg C]

After 40yrs of procrastinating I finally got myself a chronometer. True to my life philosophy, I got one of the least expensive models on the shelf- and now I'm kicking myself for not spending a little bit more! Since my new tool doesn't do anything except measure speed, I'm having to do the calculations myself. When working up the SD, we begin by first getting the average velocity , and then getting the deviation of every shots velocity from the average velocity. Does it matter if the actual shot is slower than the average?
I think I just answered my own question-it's a deviation, am I right ? It doesn't matter which way it deviates, it is still a deviation. Is that correct ?
Then, as the formula states, average the deviation. Is this then the Standard Deviation ? Or is it only an average ? Does it matter ?

 

[Pdvdh]

Google research "Standard Deviation". Locate the proper mathematical equation. Use it to calculate SD.
If you have a computer with the Microsoft Excel software program, it includes formulas for calculating standard deviation.
Which chronometer are you using? Find it in a cave? Sorry...

 

[WeiserBucks]

Since you're new to using a chronograph, my advice is DON'T SHOOT THE **** THING! Sounds simple enough, but people shoot them all the time, I saw several one shot kills at my local range this year .

 

[Pdvdh]

Some of the low cost/quality Chrono's are good for nothing more than target practice.
If you hit it, you'll know a bullet exited the barrel, but not the MV. Which is the same info provided by a cheapo Chrony.

 

[Gregg C]

Google research "Standard Deviation". Locate the proper mathematical equation. Use it to calculate SD.
If you have a computer with the Microsoft Excel software program, it includes formulas for calculating standard deviation.
Which chronometer are you using? Find it in a cave? Sorry...

Oh that's funny! I guess that is close, since I AM a dinosaur!
It's a Shooting Chrony F1, and I began to see after the first shot that I need to at least get the plug in remote, since I had to step up to the firing line and lean across it to read the speed ! Getting old really sucks !
Any way, thanks for the quick response. I downloaded that app and am going to need to take some time to learn how to utilize it. Probably need to do that Google search, too....who was it that said Ask mme for anything but time ? I can see also how valuable of a tool I chose to deprive myself of for all these years. The es needs some attention, at 37fps, so right away I'm learning something. Heck, I was even under estimating the speed by a LOOONG ways. I thought it should have been around 3100fps...imagine my shock seeing 3489 in the display !

 

[Gregg C]

Since you're new to using a chronograph, my advice is DON'T SHOOT THE **** THING! Sounds simple enough, but people shoot them all the time, I saw several one shot kills at my local range this year .

That seems like sound advice, for sure ! Oh yeah, forgot- these guys will accept a shot up Chrony in trade !!! I guess if I had managed to hit it, I would still be to get those upgrades ! LOL Thanks

 

[Gregg C]

Some of the low cost/quality Chrono's are good for nothing more than target practice.
If you hit it, you'll know a bullet exited the barrel, but not the MV. Which is the same info provided by a cheapo Chrony.

I understand that old adage you get what you pay for, but I don't consider $115 throw away cheap. They had another manufacturer on the shelf for about $20 less, but Shooting Chrony has been around for a long time, been alot of ammo shot across them. I have been lurking around on this site for a few years, and I have seen folks posting problems with just about everything under the sun. Seemingly, nothing is perfect. So. How would a person go about verifying the readings ?

 

[Pdvdh]

A second chronograph run concurrently. Or a Magnetospeed or Labradar run concurrently.
I know... more money...
I run a triplicate chronograph setup, one of the three being an Oehler 35P. Which means I receive four recorded bullet velocities for each bullet fired. In this manner I can easily ID suspect recorded velocity from any of the three chronographs. Not saying that's the ticket for you or anyone else.
If you experienced a 389fps surprise in MV, I would wonder if that recorded velocity is realistic for your cartridge and bullet weight? That's a large surprise.

 

[Barrelnut]

Seemingly, nothing is perfect. So. How would a person go about verifying the readings ?

You verify by shooting longer ranges and verify that the drops match what the velocity of the bullet should be in a ballistic app with the BC of the bullet.

So for example, if zeroed at 200, shoot at 300 (400 even better) and verify that the drop matches the bullets speed from the chrony. It rarely does. You will probably have to make some final adjustment to the chrony velocity in the app to get everything to line up. It is also good to verify at all ranges you anticipate shooting at.

 

[LoneTraveler]

A chronograph is an eye opener. The first time I dealt with a chronograph was at a range several years ago. A guy there was testing some new loads. When done he asked if we wanted to shoot our rifles over it.
My brother shot his 338 WM over it. Every so often he would have a shot drop about 4 inches low right out of the group at 100 yds. The chronograph told the story of the drop shot. Brothers load was 225 gr. bullet at 29?? fps then this one shot went 27?? fps. Shot hit 4 inches low right. Traced it to bad primers and changed primers, Urika. Went and bought me a chronograph in a couple months and I like to shoot through it. Now I take my chronograph to the range and shoot through it a lot, Especially when changing powder or primer lots.

 

[Gregg C]

A second chronograph run concurrently. Or a Magnetospeed or Labradar run concurrently.
I know... more money...
I run a triplicate chronograph setup, one of the three being an Oehler 35P. Which means I receive four recorded bullet velocities for each bullet fired. In this manner I can easily ID suspect recorded velocity from any of the three chronographs. Not saying that's the ticket for you or anyone else.
If you experienced a 389fps surprise in MV, I would wonder if that recorded velocity is realistic for your cartridge and bullet weight? That's a large surprise.

A second chronograph run concurrently. Or a Magnetospeed or Labradar run concurrently.
I know... more money...
I run a triplicate chronograph setup, one of the three being an Oehler 35P. Which means I receive four recorded bullet velocities for each bullet fired. In this manner I can easily ID suspect recorded velocity from any of the three chronographs. Not saying that's the ticket for you or anyone else.
If you experienced a 389fps surprise in MV, I would wonder if that recorded velocity is realistic for your cartridge and bullet weight? That's a large surprise.

Thanks for the response. It was a large surprise. The cartridge is 338-378 Why, the barrel is 32in, powder 114grs Retumbo, bullet 225 Hornady SST. Put some 265 Barnes bullets across it too. Also faster than anticipated.

You verify by shooting longer ranges and verify that the drops match what the velocity of the bullet should be in a ballistic app with the BC of the bullet.

So for example, if zeroed at 200, shoot at 300 (400 even better) and verify that the drop matches the bullets speed from the chrony. It rarely does. You will probably have to make some final adjustment to the chrony velocity in the app to get everything to line up. It is also good to verify at all ranges you anticipate shooting at.

You verify by shooting longer ranges and verify that the drops match what the velocity of the bullet should be in a ballistic app with the BC of the bullet.

So for example, if zeroed at 200, shoot at 300 (400 even better) and verify that the drop matches the bullets speed from the chrony. It rarely does. You will probably have to make some final adjustment to the chrony velocity in the app to get everything to line up. It is also good to verify at all ranges you anticipate shooting at.

Thanks for your response. I plugged all that into Shooter, and it all seemed copesetic with the distance I was able to reach at this range, which only goes out to 200yds. Figured I would check it farther out on another day at a different range soon as I can. These are just what I consider plinkers, but they shoot pretty well, so thought I would continue to fine tune it just for grins. And experience ! Gotta get that TIME in ! Thanks again.

 

[Pdvdh]

You verify by shooting longer ranges and verify that the drops match what the velocity of the bullet should be in a ballistic app with the BC of the bullet.

Try to confirm you have an accurate BC value before proceeding. Otherwise both BC and MV will be unkown and you'll be chasing your tail.
One purpose of an accurate, established, measured MV is to eliminate that unknown. And to not have to estimate MV by bullet drops under all the sources of additional error affecting long range bullet impacts on distant targets. Which can include wind error, BC value error, scope turret value error, light refraction error, shooter caused error, etc.

 

[Canhunter35]

Thanks for the response. It was a large surprise. The cartridge is 338-378 Why, the barrel is 32in, powder 114grs Retumbo, bullet 225 Hornady SST. Put some 265 Barnes bullets across it too. Also faster than anticipated.

Lol that's what your shooting? A chrony will pay for itself in no time in helping you get your dope correct.
While the mv can be wrong because of sun angle, shadows etc, generally in a session a chrony is reliable in showing sd and es of a load. You always have to actually shoot it to verify you dope, but it gets you darn close.

 

[Shootin4fun]

One thing you can do with the 2 screen chronos like the Pro Chrono, Shooting Chrony, etc. (especially at only $120) is to shoot some rounds with it 10' from the muzzle and then put it out at 100 and 200 yards right in front of the target, and shoot through it there. I've done that with a few rifles and was actually surprised to see it closely follow the ballistic tables (Nikon Spot On) for a 7mmRM and 243 Win. Be sure you can shoot 1 MOA or better groups consistently at 200 before trying this at home kids! It's fun though.