Chronograph & PF

[ivanhu]

Jim, Your proposal?

Jim usually have no proposals but sharp criticism , but let me give you mine.

IMHO, it must be determined how we use the scale readings, and how we use the chrono readins. These are the areas what should be addressed first and foremost, as this is where the chrono guy would have the most freedom. My proposal: readings must be rounded up to the first decimal number (if there were more), and should be used so.

Whether we'll round/truncate the number we get after some maths with those readings, makes not much difference. If we allow one decimal digit both for the velocity and the weight, then the final result may have five decimal digits at most. I'd say round it up to two decimal digits, and use it that way. 164.99 is minor, period. What's wrong with that?

[diehli]

I think sigfigs and all that it implies is the way to go here. >165.0 (or 170.0 or 160.0) = major. <165.0 (or 170.0 or 160.0) and >125.0 = minor. This goes along with the XX9.95 that shred mentioned.

The potential error due to time constraints and needing to chrono at different times of day seems to be the major concern. Should there be an arbitration process for those that go minor at the chrono station? Should more rounds be taken, logged in, and shot at a later time when the temperature/humidity/barometric pressure is more optimal for the load? How do we determine what that optimal situation is?

[shred]

Ivan. No. "124.99" is unsupportable given the current equipment. Would you zero somebody shooting what the calculator says is 125.01 PF? Both numbers are identical given the available significant figures. Anybody that doesn't understand this, please investigate before posting about it.

300lb: I believe competitors are required to shoot PF at all times, thus chronoing them at any time is allowed. Some shooters may get the benefit of better conditions.. a pesky MD might re-chrono the squeakers at another time if desired.

[Jim Norman]

Two items, first there really are two questions being asked, one is what tolerance if any is allowed based upon the rounding of numbers provided and iss there a rule required to address this. I suppose that there could be a need for that type of rule? I thought 165.0 was the floor, (or what ever IPSC might require since I realize there is a difference) 164.99 is not 165.0 If I owed yo money, you would ask for the penny, I you gave me 165.1 I would say you were overpaying. Same rationale applies.

The second has to do with the equipment being used. I am adressing this from the point of view of the equipment I have seen and used. 1/10 grain of weight and whole feet, keep the 1/10's in the initial calculation and keep only the first 1/10's at the end. No rounding, you either make it or you don't.

A more lengthy explaination follows,

Actually I thought I was quite clear. Unless I am mistaken, don't most chronos that are in general useage by the general public read whole feet per second? And don't most Ohaus scales electronic or balance read in 1/10 grain? (Or equivilent?)

Now that having been said, I might see where if the equipment provides a greater number of decimals when used in the metric mode, ie., fractional meters per second, vs whole feet, that could have an effect on my earlier statement. But when applied to the US, where grains and FPS are the standard, the equipment reads in 4 significant digits. You don't extrapolate 1/100 of a grain in the reading, it is either 0.1 or 0.2 as an example, the FPS is whole feet, the math then is simple.

Besides, as someone else said earlier, if you want to cut it so close to the bone, then maybe you deserve to be caught out. The argument that the same ammo in a similar gun fired at a different time does not hold, you have changed at the very least two variables. Even if you fire at the same time, you have no less than one difference, the barrel could be faster or slower and there is always the minor difference between rounds.

I would propose that we count 1 decimal at the maximum when using grains and the whole number in FPS.

An example: 125 grain 9mm head at average of 1000 fps is exactly 125PF, if I shoot a 125.1 at 999 fps, I get 124.9749. The question becomes one of tolerances. IF we decide that there is a tolerance, then we need to decide how much. If we on the otherhand decide that since the most accurate information provided was to only one decimal place, then we can only accept the answer to that same one decimal place and this example would then become 124.9. Period, end of discussion. We either set a standard or we do not.

Now if the Chronodude rounds the inputs, the shooter gets an even worse outcome in this example, 124.8 still minor since we assume he rounds to the nearest whole number.

If any rule is required, and I am not sure one is, It would be that the numbers used are as reported by the measuring equipment to one decimal place where decimals are provided and as whole numbers otherwise.

As long as the above is followed, should there be an arbitarion? I say NO. Your ammo should be expected to make Major or Minor at anytime it is tested. If there is a question that you are using "Chrono Rounds" it should be allowed that the MD can pull you out for a re-chrono using the last mag you shoot from. Or one you dropped on the stage you just shot if the last mag is empty.

Is that solution enough for you Ivan? or do you still see this as only criticism?

Jim

[Yoda]

Should there be an arbitration process for those that go minor at the chrono station? Should more rounds be taken, logged in, and shot at a later time when the temperature/humidity/barometric pressure is more optimal for the load? How do we determine what that optimal situation is?

300LB,

I think there is no need for arbitration if a competitor doesn't make the declared PF. The chrono procedure already gives the competitor the benefit of calculating with the 3 highest velocities out of 7 if the competitor doesn't use his last round to weigh the bullet again. That means that out of 7 at least 5 rounds don't make the required PF. IMHO that is more than enough margin. Besides - as Shred already pointed out, the ammo should make the PF all day long, anytime!

[Skywalker]

If any rule is required, and I am not sure one is, It would be that the numbers used are as reported by the measuring equipment to one decimal place where decimals are provided and as whole numbers otherwise.

I'm sure it is needed (since it lacks in the rulebook), and actually it's up to the chrono guy to decide how to use readings.

Yours is a proposal that allows some flexibility with respect of the equipment used (usually chronos will display a decimal when velocity is below 999.9 fps, but only integer figures with velocities above 1000 fps), and doesn't involve rounding or truncating of the final result, but only rounding of the input data where more decimal digits are available.

[schoonie]

Guys,

Why not use all the numbers that the equipment in use at the match is capable of? No rounding. no truncating, just use all the numbers. The final result is unadulterated and is consistant for all shooters for that match. The integer of the final calculation is the answer, you either made it or not.

[shred]

Guys,

Why not use all the numbers that the equipment in use at the match is capable of?  No rounding. no truncating, just use all the numbers.  The final result is unadulterated and is consistant for all shooters for that match.  The integer of the final calculation is the answer, you either made it or not.

Ai! Yi! Yi!

"All the numbers we generate" is the problem. All those decimal places look cool, but don't mean squat in reality.

We are trying to determine when a fuzzy dot crosses a line. Nobody is debating where the line is, it's how to determine when the dot crosses it and the size and fuzziness of the dot that we're debating.

Jim's got it right. We need a tolerance because there is one in the measurement equipment. We're proposing that be roughly +/- 0.05 PF points. In reality, that is less than the tolerance of the equipment, but going to +/- 0.5 irritated too many people that like to see their friends in pain.

My latest rule proposal goes like this:

Power factor will be calculated using measured velocity and bullet weight.  The final result will be rounded to the nearest tenth.  For example 124.94 rounds to 124.9 and 124.95 rounds to 125.0.

[Skywalker]

Guys,

Why not use all the numbers that the equipment in use at the match is capable of?  No rounding. no truncating, just use all the numbers.  The final result is unadulterated and is consistant for all shooters for that match.  The integer of the final calculation is the answer, you either made it or not.

Then I might ask "what's the purpose and need of the time decimals (2) specification in rules 9.2.2.1, 9.2.3.1 and points decimals (4) specification in rule 9.2.5"?

Why don't we use the numbers that the equipment in use at the match is capable of? If at match a timer recording .1s only is available, why don't we use that? Why do we feel the need for greater accuracy?

If there is a rationale behind choosing a minimum level of accuracy in readings, the same shall apply to all match equipment, not to timers or stage points calculation only.

[kimel]

Let me toss something else in here all of which relates to calibration of equipment.

Scales are not a problem. Calibration weights are available from many, many sources. We probably do need to add in a procedure where the calibration of the scale is checked every so often and recalibrated if necessary. I don't think a calibration check between every competitor is too often. It doesn't take much time to toss on a 100gr calibration weight, check to make sure it reads 100.0 and move on. As competitors we can all ensure that our home scales are calibrated in the same manner with quality calibration weights and be pretty sure of the outcome when we get to the chrono stage.

Chronographs are a whole other kettle of fish. I know of no way to calibrate a chronograph which can be accomplished by anyone, anywhere without a ton of expensive equipment.

IPSC has no standards about chronographs and their baseline accuracy...at least that I can find in the rules. Only that they are somewhat consistent from day to day.

Where is the standard that ensures that the chronograph being used is actually accurate to some standard? By the rules, I can go build a chronograph in my garage using some simple electronics, stuff it in a box and it is just as legitimate a match chronograph as the most expensive commercial chronograph going. Or I can show up with the Chrony that has been bouncing around in the back of my truck in the gear box for 3 years and it is a legitimate match chronograph. (And no, my chronograph doesn't bounce around in the gear box)

So the chrono says that bullet was travelling at 1000 FPS. Was it really? Maybe the electronics are faulty, the battery is weak, or the sky screens are not set to the proper offset. Maybe that was really 1100 FPS or 900 FPS. No one knows for sure.

All the decisions about rounding up/down, truncation, etc. don' matter one tiny bit if the equipment used to take the measurements is faulty.

We tend to trust our digital displays and the people that make them but this is blind faith.

We all develop our loads based upon our own chronographs blindly trusting that the display isn't lying to us. That is bad enough but to blindly trust the chronograph at a match is just plain silly.

[Yardbird]

Well, I'm no math wiz and I am getting a bit confused with this discussion, however, in the original post Shred stated that there is a potential fudge factor of .15 in these calculations and if this is the bottom line and the point to this whole thread then couldn't you just calculate the PF using whatever equipment you have in the usual way and then add .15 to eliminate the potential error and get the official PF?

[Vince Pinto]

Now do you see why it takes 12 months, 7,000 emails and 4 days of face-to-face meetings to produce a decent rulebook?

As to a decent rulebook, obviously a lot was moissed and now we are faced with "Fixing" a problem via a rules "Interpetation"

Folks, in an effort to avoid confrontation, I'm voluntarily withdrawing from this thread.

[ivanhu]

Ivan. No. "124.99" is unsupportable given the current equipment. Would you zero somebody shooting what the calculator says is 125.01 PF? Both numbers are identical given the available significant figures. Anybody that doesn't understand this, please investigate before posting about it.

Why unsupportable? The question is, how much diversity we're going to eliminate mathematically.

Suppose I have two shooters. Bullet weight is the same: 124.9 grains.

The velocities:

1002 fps, 999.1 fps, and 1001 fps for the first shooter;

1002 fps, 999.5 fps, and 1001 fps for the second shooter.

That is, the average velocity (rounded up to one digit): 1000.7 fps, and 1000.8 fps.

From that, the calculated pfs:

first shooter: 124.9874 - rounded to two significant digits: 124.99;

second shooter: 124.9999 - rounded to two significant digits: 125.00.

Therefore, the first shoots for no score (pf 124,99), and the other is scored minor (125,00). What's wrong with that? After all, the velocity is the average of three speeds. That for me means that one of the shooters loaded his bullets slightly hotter (or was just luckier on the chrono stage). But these are the chrono readings.

We might debate how wide the gap should be; that is, how many significant digits we might allow. The less we allow, the bigger differences it eliminates. But why should we eliminate it on the first place? What you're trying to do is to eliminate the affects of the different temperature, whatever.

Would it be 1 significant digit, the second velocity of the first shooter might be 998.3 fps to shoot for no score, and any higher would do.

Would it be 0 significant decimal place (that is, round number), the second velocity might be 987.3 to shoot for no score, and any higher would do.

That is, using 2 significant digits, we eliminate approx 0.1 fps differences;

using 1 significant digit, we eliminate approx 1 fps differences;

using 0 significant decimal place, we eliminate approx 10 fps difference.

I have no problem with the first; even the third won't eliminate the affects of the temperature, humidity, etc. changes (multi-day matches we have), while the first resembles most the current system.

Further, I don't understand that "zero somebody shooting what the calculator says is 125.01" part, please clarify.

[EricW]

5 pages of damning evidence that nobody (myself included) TRULY understands the significance of the output of a chronograph.

Before we start blabbering away about decimal places and significant figures (the CORRECT method) - it would seem that we would need to understand the true level of accuracy of the chrono and the scale. Those two pieces of information drive how we do everything else.

My 2 rubles...

[shred]

Suppose I have two shooters. Bullet weight is the same: 124.9 grains.

The velocities:

1002 fps, 999.1 fps, and 1001 fps for the first shooter;

1002 fps, 999.5 fps, and 1001 fps for the second shooter.

That is, the average velocity (rounded up to one digit): 1000.7 fps, and 1000.8 fps.

From that, the calculated pfs:

first shooter: 124.9874 - rounded to two significant digits: 124.99;

second shooter: 124.9999 - rounded to two significant digits: 125.00.

Therefore, the first shoots for no score (pf 124,99), and the other is scored minor (125,00). What's wrong with that?

The problem is shooter #1 could be shooting 1002 fps, 999.1 fps and 1001.4 fps and it will look EXACTLY the same on the chrono display, but their REAL PF will be 125.004. You just zero-scored somebody that was truly shooting Minor. Happy now?

[ivanhu]

The problem is shooter #1 could be shooting 1002 fps, 999.1 fps and 1001.4 fps and it will look EXACTLY the same on the chrono display, but their REAL PF will be 125.004. You just zero-scored somebody that was truly shooting Minor. Happy now?

I couldn't care less. First, it's the same for all. Second, the chrono is far less accurate than that even on the same day, depending on the time; therefore, while it makes sense to me trying to eliminate the diversity the circumstances mean, it doesn't make much sense to correct one problem on the unproper way. Third, all the shooter should've had to do is to load his rounds a bit hotter. If he's going to be this close, he deserves the penalty. Next time he'll know better.

For your problem the only solution could be to add 1 fps to each reading above 999, because the bullet might be faster than the showed reading. That's a kind of compensation I don't really like, taking counter-actions because of considerations.

Sorry, I still cannot buy your reasoning to use rounding in order to eliminate one supposedly unfair feature of the chrono. Increase the reading by one, and be happy with that - that's the only solution to your problem IMHO. Correcting the makings by artificial ways, that's kinda like socializm. On the surface it sounds well, but when you're in it - nope, you don't really wanna know...

[shred]

Ivan, I normally agree with you, but you don't get it this time. Please go study up on significant figures and scientific measurement and come back when you understand that for our purposes with the equipment we've got 124.99 IS THE SAME AS 125.0. Two decimal places is MEANINGLESS, yet you persist in assigning meaning to them.

And I already banned "They shouldn't be that close anyway" as an irrelevant argument. Political arguments are banned by forum rules. This is math and science. I'm sure they have that where you're from.

[ivanhu]

Ivan, I normally agree with you, but you don't get it this time. Please go study up on significant figures and scientific measurement and come back when you understand that for our purposes with the equipment we've got 124.99 IS THE SAME AS 125.0. Two decimal places is MEANINGLESS, yet you persist in assigning meaning to them.

Listen, first of all, I know what are the possible readings on the chrono, and I made the math. Two decimal places is not meaningless - we have three readings, we sum them up, then divide them by 3. That might result an infinite line of decimals, and it might mean life or death how many of these decimals I use when I further multiply this average by the weight.

Since the readings are the same for all, therefore, we must deal with those readings. I don't care whether the chrono rounds up to the nearest thousand, as long as it does it consistently. I don't care whether the shooter's ammo is really 125, or just 124.8 or 125.9, were I use very expensive tools to measure its speed. All I care is that I want a consistent way, which is the same for all, to calculate the PF. Whether it says 5 above for all, or 4 below, I don't really care. Some might suffer if they were that close to the limit. So what? Next time they won't push the envelope.

Once more. I don't want space science to ensure that the PF we calculate is absolutely accurate up to 10 decimal places. All I want is a consistent method, which treats all of the competitors equally.

Hope you understand now. Just as you cannot say "oh, but with my chrono it made the PF", you also cannot say that "using those high precisity expensive laboratory radar tools, the ammo would make the PF".

I cannot explain it more clearly.

[shred]

Please go away and come back when you understand significant figures.

I mean this in the nicest way.

[jhgtyre]

Okay. Why don't we just lock this one? I know I have a significant desire to lock it.

-ld