Chrono Picking

[Chris iliff]

Well, I just got back from Area 6. I will start by saying what a fun match and great staff. Now to my dilemma, I went "minor". Boy, that screwed with my head, and I let it suck my natural aggression right out of my performance as I was afraid to miss, or hit a "no shoot". I did shoot a clean match, so that was a positive.

Anyways, the first thing I do when I get back to Indiana is chrono my rounds again. They are spot on at 171.5pf. I never play the game with PF, I always thought that 6.5pf over was a pretty good buffer. Won't happen to me again.

MEAT: Driving back I was thinking about the procedure for picking the match chrono. I was thinking that big matches should have 2, from different manufacturers, in line with each other and an average of both should be used. Or, maybe the highest. Or, at least several compared to each other and the highest averaging chrono used for the match.

I have extensive training in metrology, (calibration) of electronic equipment, and have run a type 2 lab and worked extensively in type 3 cal labs. I know that even from the same manufacturer 2 identical pieces of electronic equipment can and will give very different measurements. This is what got me thinking about using more than one and averaging. Or, testing several before the match and using the one with the highest average.

The 2 men at Area 6 running the chrono where extremely professional, I actually felt sorry for them feeling bad for me. The procedure was spot on and I can't complain about how USPSA set the rules. But with my background in metrology, I feel we could do more equipment wise to benefit the shooters.

What say you?

Edited to add: 164.1pf, close but no cigar!

Edited April 21, 2010 by fourtrax

[Chris Keen]

A chrono is like your gun ..... you gotta "get to know" what it likes / dislikes. It may run high, or it may run low. But the important thing is that it is consistent. And in order to know this you will have to give it some time to figure out where it is in relationship to other chronos.

When you go to a match and get chrono'd bring your chrono results back home and compare. After doing this from 3 or 4 matches you should know whether your chrono is hi / low / spot on. But you can't be playing around with your load in the mean time either. Consistency is the only way to get to know your chrono. But I shouldnt have to tell you that if you're used to running a lab, right?

[SLM]

What day did you shoot? We shot all day Saturday. The chrono setup was two CED's in line and they took the velocity from the highest reading one. IIRC the display on the right side of the two showed fastest on all three of my rounds. This is pretty much the standard setup at any major I've been to. Two set up in a row, take the velocity from the highest reading one.

What brand of chrono do you have? I have a CED with regular sensors and my loads were right where they should have been, maybe a tad faster which I'm attributing to doing my load development in the snow a couple weeks ago (~35F the day I checked) verses the 90F it was Saturday afternoon.

[G-ManBart]

Most matches do have two chrono's in line and you get the higher of the two readings. I've actually seen one shot taken from one chrono and the next shot taken from the other, which completely had me confused, but it's a pretty common setup at big matches. I think trying several and picking one that gives the highest readings, while helping competitors the most, isn't necessarily representative of the truth, since that one is probably reading higher than what the bullet is really going.

You experience is why I've harped on it over and over that ammo in the 169-171 range, that sooooo many people think is perfect, isn't enough of a cushion. I always describe my experience from the 2008 Nationals and it still doesn't make much sense, other than it happened. I loaded a big batch of ammo for Nationals, a Sectional and an Area match....all the same lot of powder, same lot of bullets, etc. That load was consistently 173-174PF in both my testing and all of the matches except the Nationals, where it went 166.1 Using the same batch of components (yeah, I buy in major bulk) I loaded my ammo for the 2009 Nationals, not having touched anything on the press, and it went 172PF if my memory is correct. I don't know where those 75fps went in 2008, but they went somewhere! R,

[sperman]

Appendix C2 of the current USPSA rulebook covers the chronograph rules and procedures.

[Sarge]

As much as it pains me, I agree with Bart. I only shoot minor so I aim for 135 with my loads. If I find a good accurate load I'll even move closer to 140. The dumbest thing I saw and heard at the A6 this week was various shooters worrying about chrono! It is the last thing I even want to think about especially at a major.

As for chrono's not matching up perfectly. Well, thats why they use two and give you the best numbers. I use a pro chrono and am happy with it. One of the things I like most about it is the fact that it almost always reads a few points low compared to match(CED) chronos. This gives me some built in margin. As a matter of fact for A6 I loaded some ammo that ended up being hotter than expected(140)so I dropped the charge .2 and loaded it up only to go 141 @ A6. And that is with TG which is temp sensitive. Funny thing is it was almost 80 degrees when I chrono'd it and it was less than 65 the morning it got checked @ A6.

Anyway, the moral of the story is stay well away from minimum PF for a much less stressful match.

Edited April 21, 2010 by Sarge

[BillD]

I use a Chrony. I tested 30 rounds, threw out the highest and lowest and averaged the rest for a 172.6PF. When I was chrono'd

at Area 6, I made 178PF with my bullet 4 grains lighter at Area 6 than my weighing. I weighed 10 bullets on a $15K, PM'd, calibrated scale and they all weighed within .1 of 206 grains.

Moral of the story, everyone's chrono and scale are different.

[XD Niner]

My chrono (Chrony Beta Master) usually reads 1-2 PF greater than the CED's used at most matches. Based on it's readings, I load to 172 PF as a consequence.

I can't tell the difference between a 168 and a 175 PF round by feel assuming all else is the same. I really doubt that we can tell a 3% to 5% difference in PF by our sense of feel alone.

Edited April 21, 2010 by XD Niner

[Chris iliff]

I did not notice the two chrono's and thought they shot thru one. I have went back and compared my chrono results and another guys who has used my chrono against our at home readings and our match readings. This was something that I have never done as I have never gone minor before. But interestingly, it seems that our readings are tracking the same. That is, at home we are both in the 171-173 range and at the matches we both go low 165-167. I guess I just never thought to check that out. Now I know that my at home chrono is running about 55-65fps fast, I will make the adjustments.

Bart you are spot on and I learned the hard way, I would say a buffer of 10pf at the least now. My buffer at A6 was 6.5pf.

Mr. Keen, I have not run or worked in metrology for 19 years, so forgive me for not maintaining critical thinking skills. Your jab at the end of your post actually felt like a kick in the groin..... thank you, I will not need another on this subject!!

I have a F-1 Shooting Chrony. Edited to add,, I shot all day Saturday.

Edited April 21, 2010 by fourtrax

[pjb45]

What was your powder? Does temperature have an effect on it? What was the condition of your barrel at the match v. home chrono? Start looking at some environmental reasons for the differences also.

[Dave S]

I found it very ironic that at area 5 (both this year @ Polo and last year at Michigan) the chrono was two CED set up in tandom, the RO shouted out the higest of the two, but then when he figured the average, he took it off only one chrono box rather than doing the math by hand. Go figure. What's the point of two?

Edited June 21, 2010 by Dave S

[SLM]

If you watch the numbers it's almost always one that reads higher than the other. They call out and record the velocity in case something happens to the chrono. If you were to have a round or two read higher on one and then the other chrono read a round higher I'd guess they'd do the math by hand. I've never seen that happen though. One has always been faster on all three rounds so no reason to do the math by hand.