Chrono Certification

[kgunz11]

How is a match chronograph certified and calibrated?

[JThompson]

How is a match chronograph certified and calibrated?

By using two of them...

[ima45dv8]

I use sub-minor ammo in the 115 PF range. Each morning the same lot of ammo is fired over the chrono and the results are recorded. If it varies by more than 4% the chrono will possibly get tossed for that match.

See appendix C2 for all relevant details.

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I forgot to add how entertaining it sometimes is for folks to lose a popper calibration challenge and learn it just fell with sub-minor ammo. There were a couple of times I wish I'd had a camera.

[Corey]

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I forgot to add how entertaining it sometimes is for folks to lose a popper calibration challenge and learn it just fell with sub-minor ammo. There were a couple of times I wish I'd had a camera.

been there, seen that ( not me but a squad mate). two shooters on the same stage had issues. both time they were proven wrong and just looked kinda dumb-founded.

[kgunz11]

I use sub-minor ammo in the 115 PF range. Each morning the same lot of ammo is fired over the chrono and the results are recorded. If it varies by more than 4% the chrono will possibly get tossed for that match.

See appendix C2 for all relevant details.

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I forgot to add how entertaining it sometimes is for folks to lose a popper calibration challenge and learn it just fell with sub-minor ammo. There were a couple of times I wish I'd had a camera.

But how do you know that it's 115pf ammo?

Using 2 chronos back to back does help validate things. I know there are some folks that are "traveling chrono guys" and always use the same chrono and I've only heard of one match with the chrono stage getting thrown out.

[Pezco]

The only true way is to have ammo or a projectile that moves at a known velocity. I don't know of such a beast at this time, but I will be helping with chrono next month and guy that will be leading that stage has more experience so I'll ask him.

[ima45dv8]

But how do you know that it's 115pf ammo?

If I run it over two back-to-back CED chronos, how do you know it's not?

At some point we have to stop trying to see how fine a slice we can make from a tomato and run with what's in front of us. Today's chronos are the best reasonably-priced tool we have available, and if we don't invest a little faith at some point, what would you suggest as an alternative?

They beat pure hell out of the Ballistic Pendulum.

[kgunz11]

"Running it over 2 chronos in tandem" would be the answer to my question right?

I've witnessed many erroneous chronographs. Mark K chrono'd his ammo before A6 and went minor (160pf). The chrono he used said he was at 180pf. After A6 he took his ammo back to the range and shot it again, and again it was 180pf. So he acquired another chrono, again 180pf. He set 2 of them back to back and they were within 12fps of each other.

Then again, they could have measured one of his 200gr bullets incorrectly, or punched it in the calculator wrong. He and I both are still trying to figure it out. I'll be taking MY chrono to the range Saturday so he can get an accurate velocity. My chrono doesn't care how much light it does or does not have and doesn't have to be mounted in a silly box. Maybe we'll be closer to getting to the bottom of this.

[Corey]

super high speed cameras and those black and white boards on the side like you see on mythbusters all the time will give you an exact measure of actual FPS. Could be a bbiiiiiiiiittttt expensive for most clubs tho....

Personally, im fine with sticking a couple $200 chronos back to back and seeing what they read

[SLM]

What did Mark have the chrono guys do after his first six shots didn't make Major? If he was still minor he had the option of either shooting the eighth round or having it weighed. Shooters choice. If he had it weighed, the measured bullet weight is right on the score sheet so you know what it checked on the scale at the match.

Not trying to pick a fight but just wondering with all the hula dancing that goes into chrono how a load could come in 20 power factor lower. Two CED's, etc, etc. I'm sure the bullet weight could have been entered wrong but a simple "Um, these went 180PF at home. Can you double check the math please" would be sufficient to have the math double or even triple checked.

Anybody else this far off?

I know I was .2PF different from my CED to the match CED's and in three years I haven't been off more than 1 or 1.5PF.

[JThompson]

All this to get back to what I said in the first post....

[Skydiver]

It could also have been a keying error at the computer in EzWinScore and not at the chrono tent/stage.

When I got home from A1 last year, I noticed that I was being scored as shooting L10 Major even though I declared L10 minor. My match chrono sheet says that I was shooting minor with a PF of 132 (?). I didn't get to see the wailing wall since my housemate and I shot the entire match in one day and drove home the next morning, by the time I got a chance to check online and when I tried to contact the MD, it was already too late. Anyway, talking to the MD, the computer said that I had a PF of 174. If that PF were true, I should have been DQ'd for having "unsafe ammo" since I was shooting 9mm in Limited 10. I don't know how they got from 132 to 174, but that's all water under the bridge now.

I tend to trust the tandem chrono setup. You get the benefit of getting the faster chrono reading in this configuration based on the rules. I don't think if you can call for arb on the chrono accuracy.

[Flexmoney]

Then again, they could have measured one of his 200gr bullets incorrectly, or punched it in the calculator wrong. He and I both are still trying to figure it out.

Take your scale too.

Math works for 200g ---> 180g

[kgunz11]

He knew when he walked away from the chrono stage that he went minor. I didn't intend for this thread to be about Mark, just used his case as an example, and I hope he doesn't mind. I was just curious as to how match chronos were verified accurate. I spent a bunch of money to get a really nice chrono, because for what I do it can save me lots of money in the long run. I have a way of verifying that my chrono is accurate, but it's a long shot for most folks.

I thought they pulled a bullet and weighed one for everybody, but I know mistakes can happen and no one is to be blamed for that. I too have a hard time figuring out the 20pf. I'll be meeting him Saturday to shoot some ammo through my chrono to see if it matches the other ones he's been using. Heck we might set all 3 up and record the MV from each one and report back with it.

[JThompson]

I don't think if you can call for arb on the chrono accuracy.

Sure you can and it can be thrown out like any other COF.

Edited April 29, 2010 by JThompson

[kgunz11]

Then again, they could have measured one of his 200gr bullets incorrectly, or punched it in the calculator wrong. He and I both are still trying to figure it out.

Take your scale too.

Math works for 200g ---> 180g

He was getting 900 fps on the 2 chronos at home. I wonder if Mark got a box of bullets that were labeled 200gr when they were actually 180gr. I'll link him to this thread.

[Corey]

make sure you weigh a random selection from new boxes and that wont happen.

I know that almost every one of my Precision 200 gr bullets actually come in right around 199.4-199.9ish. slightly under 200 but all fairly similar (at least the 30 or 40 that i weighted were. if Im ever close to the edge, depending what the weighted bullet went, Im shooting the last one...

[kgunz11]

He was suppose to be using 200gr Zeros with Clays powder. One thought was that the cooler morning temps could of had some effect, but 20 pf or 100fps?

[G-ManBart]

He was suppose to be using 200gr Zeros with Clays powder. One thought was that the cooler morning temps could of had some effect, but 20 pf or 100fps?

The biggest swing I've seen was what happened to me at the 2008 Nationals. I'd loaded up a big batch of ammo for Nats and two other big matches. It routinely went 173-174PF (like ten different days) on my chrono and at both other matches. At Nationals it went 166.1PF, which is 65fps low for that bullet weight (115gr). Using the exact same lot of cases, powder, primers and bullets (yes, I buy in major volume) and loading on the same press that hadn't had a single thing touched, the load went 172PF at the 2009 Nats....weird, weird, weird, but it happened. R,

[ajg308]

I know CED chronos get used at a major matches on a regular basis. I would suspect them before anything. Everytime I have chronoed my ammo on them they are always about 8000 lower than other chronos. ie 174k to 166k.

2008 Area 1 I shot my load at 174 pf and a SD of 7 using zeros and new starline brass. 12 hours later the CED's had me at 165.9k. I about puked when I realized during the stage how close i was to going minor.

Beware the CED!

[Mark K]

Since my situation came up.

1) I do not dispute calculation of my PF. Shooting 200gr bullets all the time makes that easy. The pulled bullet was weighted at 200.2gr (a MG bullet). Yes, this load only averaged 800fps. I watched every shot.

2) Yes, this very load tested at over 900fps the Thursday before I headed up there. The Chrono was a Shooting Chrony.

3) After Area 6, that Monday, I tested this same box of ammo across the Shooting Chrony and an Oehler Crono in tandem, and the Shooting Chrony recorded @12fps faster. I also tested various ammo I had test months before, and they tested at the same FPS that they did months ago, so the Chrono results have not changed.

4) This exact same load was 173PF at the Alabama Sectional one month before.

I was performing so poorly, that it did not matter if I was Major or Minor. My question to Bobby that day, was mostly how could this happen? I attributed it possibly to the fact that it was quite cold that previous night and probably in the 50s when tested first thing in the morning.

I DO NOT CARE ABOUT THAT RESULT. Everyone was tested across the same chrono. The testing was fair. My concern was my own - how could I depend on a legal Major load.

The powder was Clays, but I am changing back to VV N320 and Solo1000. (am tired of hearing about how dangerous Clays is for major)

But I am also interested in Bobby's basic question, How do we know when a chrono is giving us good data. The load that Mark R. might tell me works in his gun, will almost certainly be different in my gun. If the tester carries a gun with a standard ammo to test his chrono at major matches, the best that can be said is that the chrono is +/- XXfps than it was last time.

Just questions, not complaints.

Keep smiling - this is a fun sport, even on the worst of days.

Mark K

[LChico]

make sure you weigh a random selection from new boxes and that wont happen.

I know that almost every one of my Precision 200 gr bullets actually come in right around 199.4-199.9ish. slightly under 200 but all fairly similar (at least the 30 or 40 that i weighted were. if Im ever close to the edge, depending what the weighted bullet went, Im shooting the last one...

That is an excellent plan. My advice would be to always shoot the last bullet, if you are close. I have never, repeat never, seen anyone make it on the weight. And that is from nearly 20 years of experience at multiple major matches each year.

I'd be interested to hear if anyone has ever squeaked into major when the last bullet was weighed.

Linda Chico (L-2035)

Columbia SC

[Nik Habicht]

I was performing so poorly, that it did not matter if I was Major or Minor. My question to Bobby that day, was mostly how could this happen? I attributed it possibly to the fact that it was quite cold that previous night and probably in the 50s when tested first thing in the morning.

I DO NOT CARE ABOUT THAT RESULT. Everyone was tested across the same chrono. The testing was fair. My concern was my own - how could I depend on a legal Major load.

Mark K

I've got a compound questions: Shoot the match in one day or two? Did your chrono ammo spend the night, i.e. collected on day one, shot early on day two?

[Flexmoney]

My advice would be to always shoot the last bullet, if you are close. I have never, repeat never, seen anyone make it on the weight. And that is from nearly 20 years of experience at multiple major matches each year.

I'd be interested to hear if anyone has ever squeaked into major when the last bullet was weighed.

Linda Chico (L-2035)

Columbia SC

That is probably where they would end up.

I always suggest for them to do the math first, then decide. (it helps lessen the blow/frustration for the shooter too)

There really is no rush. And, we have a calculator handy at chrono. They can figure out what their bullet would have to weigh with the current top three shots.

Heck, I'd even suggest they ask for the bullet to be weighed again (in front of their own eyes)...and for the scale to be recalibrated (not just checked with the weight).

I always weigh a new batch of bullets. Zero Bullets have been boringly consistent for me. If I get something that are even a little off...I recalibrate my scales to make sure.

[Singlestack]

The CED at A6 read exactly what my CED read.

When I was looking to buy a Chrono, I looked at what was used at major matches. Then I bought the same kind.