Chronographing

[Peter K]

I am not quite shure if I am right here but here is my question:

Which chronographs are used at the nationals or other important competitions worldwide (brand and model)? Are there tolerances in the readings of the different models? I use a Chrony Alpha and I don´t know if I can rely on its readings. How can I make shure that the machine is reading correctly?

[Shooter Grrl]

There is no one set standard for the different matches to use the same chrono, hence the new "rules" for chronoing.

You really can't verify that your chrono matches every other persons.  I've personally lined up 2 and shot through both to double check, and that worked okay - both machines said the same thing.

The absolute best practice IMHO is to load to 170 :-)

[Phil Dunlop]

I haven't seen those  rules, but do they standardise the distance to the chrony, i.e. how far is it in front of the gun?

P.D.

[xcount]

Peter,

Poor man's chrono calibration check.....

Buy a box of factory ammo. Call the factory and ask to speak to one of the ammo techs.

Tell them the lot number of the ammo you bought and the gun (a stock gun would work best for this) you intend to shoot the ammo through (including barrel length). They should be able to give you a pretty good idea of what velocity to expect.

I did the once with 9mm and found my chrono was only reading 5 fps slower than what I had been told to expect. Close enough for me.

This "calibration check" on my chrono cost me about $8 and a phone call.

Or, do what Kathy suggested and set yours up in tandem with another chrono. See if there is a vast difference in readings. Then track it down from there.

[Even]

Peter,

What Kath says, translates into 175 pf for IPSC :-)

But seriously, chronographs are always variable. I run a dual chrono setup, one CED Milennium and an old Oehler 33, they are both within 5 fps of each other. Most times at matches I will be close to my measured PF, but I have on occasions been really close to minor. I always load to 5 pf over major, that’s what’s  saved me…..

Even

(Edited by Even at 1:11 pm on Oct. 8, 2001)

[jmc9x23]

At the Nationals we used a base line ProChrono, it worked well until the SO running it shot it. Good thing there was a back-up.

[Singlestack]

Even,

Why would SG's 170 translate to 175?

[DBChaffin]

Singlestack, the PF in IPSC Standard is 170 I'm pretty sure, rather than USPSA's 165.  Therefore loading to 5 over like SG recommended gives you 175.  

[ErikW]

Peter, at the recent USPSA Nationals I've attended, they've used CED chronographs. Last month, they used two, though I'm not sure whether they averaged the readings or used only one and had the other one for a sanity check.

Measuring bullet velocities with these consumer instruments is pure voodoo. It's almost a joke and it's unfair, but it's the best we can do.

[Detlef]

Chronoman takes the highest reading on each shot. No averaging is done.

--Detlef

[Even]

SS,

DB is right, IPSC major PF is 170. When they decided to lower the PF, they did it in the senseble IPSC way. Let's make two different ones for Open and Standard, rather than the USPSA KISS approach.

Even

[ErikW]

We compensate for our lack of two different power factors for Major by having two different bullet diameters for it! But only for two of the five divisions. Two other divisions allow and exclude specific cartridges. Yeah, we're keeping things real simple.

[Even]

Erik,

we do also have the different bullet diameters, 120 gr minimum for Open major vs yours 115 gr. 9x19 is legal for Open major, always has been. Open major PF is 160 and Standard major PF is 170. Same for Modified.

We play the same game, why can't we get the same set of rules?

Even

[Shooter Grrl]

---

We play the same game, why can't we get the same set of rules?

---

Patience grasshopper, it's in the works :-)  You can help by contacting your RD and expressing that opinion!

[ErikW]

I just was sent down to the Minor leagues at the Area 2 Desert Classic. First three rounds came to 159 power factor and with four more, the best averaged 161. This was the same ammo that has made 167 to 172 power factor everywhere else. As a matter of fact, this same ammo made 168 at the Limited Nationals with the same chronograph (CED) and operator (Greg Lent).

What a crock of shit! The atmospheric conditions were, if anything, more favorable to higher velocity, not lower. Last year at A2-DC it was much colder and I made 168 PF with the same lot of powder.

I mean, what do I have to do!? I load to over 170 PF at home. Do I have to load to 180 PF for the rare occurence of a bogus chronograph?

What's interesting is that of the people who were lower than expected, we were all consistently 8-9 PF lower. Yet others were dead on normal.

I count 15 of 157 Limited competitors as Minor. Is 9% unusual?

[cpty1]

I would think 9% is an unusually high percentage, assuming most of those weren't deliberately shooting minor limited.  

Did you chrono then load just enough ammo for this match?...; or chrono to determine your needed charge, then load several hundred rounds for several matches spread over a period of time?

[ErikW]

I loaded up a bunch of "big match" ammo with the same brass, same jug of powder, same lot of primers, same case of bullets.

I'm going to chrono my leftover A2-DC ammo through both guns this weekend.

[Detlef]

Greg mentioned an average of 7 % going down to minor at big matches in FS if I recall.

Doesn't Greg always use a two-chrono set-up? I've chronoed with him many times, and his procedure is to discard the low reading for every shot, and average the high readings. So, to make minor unjustifiedly, you need 2 chronos going bad. Not that this is impossible, just not likely...

168 is just cutting it too close. When I travel, I shoot for a 175 factor (180 international Standrad Div.). I don't need a tremble experience at the chrono station...

--Detlef

[ErikW]

I recall two readouts at the LimNats but I saw only one screen at A2-DC.

[EricW]

Keeping in mind that I don't own a chronograph...but I do a lot of instrumentation work, so I claim the right to be an armchair expert here...

Erik,

Did you check out this guy's skyscreen setup?  If he "rolled his own" mounting bar, the distance between the screens could be off.  Granted, 10% is a big boo boo, but it could happen.  

Not to play the blame game, but are you sure that your chrono is in calibration?  Don't ask me what the calibration procedure is, but there has to be one.  I have read where Sierra had to redo all of their ballistics tables due to a systematic chrono problem that went undetected for years.

FWIW,

Eric

[benos]

Eric,

I remember noticing two readouts at the chrono (sunday morning). My loads came in as expected...

be

[ErikW]

And you used N320? Somebody on my squad used N320 and he was dead on. I was whining to Dave Uchida about my predicament and he said N320 was really inconsistent (he made 166 at the LimNats with it) so he went to Titegroup.

I don't know, maybe my barrel is wearing and slowing down. I didn't think you could wear out a .40S&W bbl.

[benos]

Yea, 320. I didn't make the effort to test my loads before the match so I just loaded the same load I remembered using/testing in 2000 - 4.95, 180 g jhp (nosler), 1.190"  - It came in right at 170.

I have found 320 to be consistent and also good across the country (and world).

be

[Even]

Erik,

When Dave went to the chrono at the Nationals, he did not have his own ammo. I belive he got some ammo from John Flentz (and others because his ammo never showed up). I remember that several chronoed lower than expected at the Nationals, me included.

I always make sure I'm 5 PF points above what I need.

Even

[shred]

Oehler for one can calibrate chronos. Years ago, living in the same town as them, we used to occasionally run the club 35P by them.. Ken: "Well, it's 3 fps off at 10,000 fps.." us: "we can live with that". I don't know what all equipment is required, but I bet it's expensive.