Tales from the chrono

[G-ManBart]

Well, this one has me scratching my head a little bit. I'd worked up a load well before Nationals, chrono'd it a number of times and was easily making power factor with plenty to spare (172+). At Nationals I got 166.1pf...yikes! Today at Area-2 the exact same load...same batch of ammo actually, came in at 174.1pf. At Nationals, the bullet pulled was 115.4gr. Today it was 115.2gr. That means the difference in velocity was 72fps...

I know that doesn't help much, but I know why so many people talk about really low numbers at the Nationals....it happened to me and luckily I had enough margin built in. I'm sorta happy that today's numbers came back right at what I get at home so at least I know it's not that I have a crazy fast chronograph!

[ben b.]

After a local match, I tested a bunch of guys' loads, and then my own .45 loads, on MY CED. My loads, that I had develeoped using that chrono, at that range, in similar weather, loaded to 170 PF....tested at an average of 166 PF on that day with several shots below 165. I've since bumped them up to 175 PF just to save the worry.

[RePete]

Factors that can affect velocity (PF) are temperature, humidity, altitude, to name 3.

Ask yourself what was the temperature when I chrono'd them? What was the temperature at the Nationals?

The same for humidity too.

As for the altittude just google that.

[Singlestack]

Voodoo

[open17]

Had just the opposite experience yesterday. Load that I had chrono'd SEVERAL times at home. The last time

one week ago---never went below 170 PF. After 6 shots managed to eke a 165.4 out of it at Area 2. Wifes

ammo came out within .5 PF of home, same chronos for both loads, different powders.

[shred]

Humidity and altitude are pretty much irrelevant for chronoing if all the loads were loaded at the same time. Humidity can affect powder in the measure, though I've personally not noticed it.

What does vary a lot is powder lot-to-lot or even can-to-can, as well as light over the chrono. Nationals uses the CEDs-in-a-box with IR light sources. I won one of those last year and have been trying it-- on a nice day, the IR screens can differ from the regular shades by 10-20 FPS. I've not tried on less-good chrono days yet, but will be as time allows.

Temperature of the loads and gun can change things a lot depending on the powder used.

[itchy]

While trying to work up a load for IRC this year, I thought my chrono was acting funny. I kept adding powder and my PF wouldn't move. I finally set up 2 chronos, one in front of another, and shot through both at the same time. The velocities were within 10 fps. One thing to keep in mind, is the volume the powder takes up in the case and the position of the power when the round is fired. Probably more of an issue for revolvers than autos. I had a 75 fps difference when the powder was towards primer vs. towards the bullet. (I ended up shortening my oal for my 38 special).

Seiichi

[Catfish]

The chrono is black magic.

[RePete]

Humidity and altitude are pretty much irrelevant for chronoing if all the loads were loaded at the same time. Humidity can affect powder in the measure, though I've personally not noticed it.

What does vary a lot is powder lot-to-lot or even can-to-can, as well as light over the chrono. Nationals uses the CEDs-in-a-box with IR light sources. I won one of those last year and have been trying it-- on a nice day, the IR screens can differ from the regular shades by 10-20 FPS. I've not tried on less-good chrono days yet, but will be as time allows.

Temperature of the loads and gun can change things a lot depending on the powder used.

I agree with you on powder lot to lot variation, but at the higher altitude the air is thinner and the velocity will increase. And the higher the humidity the velocity will decrease. These factors do affect velocities but by how much I cab't say because I have never done a comparison test.

Another factor is the chrono itself. As shred said, the CED with IR was used at the Nats, did you use a CED or Shooting Chrony, or PACT or what?

[shred]

Humidity and altitude are pretty much irrelevant for chronoing if all the loads were loaded at the same time. Humidity can affect powder in the measure, though I've personally not noticed it.

What does vary a lot is powder lot-to-lot or even can-to-can, as well as light over the chrono. Nationals uses the CEDs-in-a-box with IR light sources. I won one of those last year and have been trying it-- on a nice day, the IR screens can differ from the regular shades by 10-20 FPS. I've not tried on less-good chrono days yet, but will be as time allows.

Temperature of the loads and gun can change things a lot depending on the powder used.

I agree with you on powder lot to lot variation, but at the higher altitude the air is thinner and the velocity will increase. And the higher the humidity the velocity will decrease. These factors do affect velocities but by how much I cab't say because I have never done a comparison test.

while technically true, there's only 10-20 feet of air between the muzzle and the chrono. I ran the numbers a while back. The velocity loss going through that much air at sea level is only about 5 fps. Even going to 20,000 feet will only drop it to ~2 fps. thus I claim its pretty much irrelevant for chronoing. For long range, yes there's a big change.

[RePete]

I realised that after I made my post.

[Neomet]

I'm wondering if it could be temperature related. Did you shoot chrono first thing in the morning? It was pretty chilly.... (yeah, I know, I've turned into an AZ pansy where if temps drop below 50 I'm looking for a winter parka)

I shot 175.1 through my CED a week ago and was 174.6 at the match shooting at 1:45 in the afternoon.

[G-ManBart]

I'm wondering if it could be temperature related. Did you shoot chrono first thing in the morning? It was pretty chilly.... (yeah, I know, I've turned into an AZ pansy where if temps drop below 50 I'm looking for a winter parka)

I shot 175.1 through my CED a week ago and was 174.6 at the match shooting at 1:45 in the afternoon.

I did think of that. The temps were pretty close between home and the nationals (afternoon) and if anything, it was colder at home (compared with nationals) the last time I chrono'd that load. It was maybe 10 degrees warmer at Area-2, but I got the same numbers at home, so the small temp difference didn't seem to change things. Oh, the powder is N105, which I haven't heard of as being particularly or unusually temp sensitive. R,

[larry cazes]

My Super load uses 7.8 grains of ramshot silhouette in SC cases with MG 124 grain JHPs. Chrono'ed 172 pf average at home the week before and 171.5 at Area 2. We hit the chrono at 10:00 am or so on saturday so it was probably 70 by then.

[uscbigdawg]

I made the ol' man proud at Area 2. My extreme spread over my 3 shots....0.

1,373 fps with a 124.1g bullet.

At home...my chrono showed 1,389.

Rich

[RickRak2000]

I chronoed my loads on Thursday up at the main range (Area 2) with a ProChrono. 169 to 171 PF

It has always been pretty close to the CED's.

When I hit the Chrono Stage they shot all 7 of 'em and I ended up with 164.7 Argghhhhhhh!

Very similar conditions and temperatures.

Black Magic, I guess... or bad luck

[ChuckS]

I chronoed my loads on Thursday up at the main range (Area 2) with a ProChrono. 169 to 171 PF

It has always been pretty close to the CED's.

When I hit the Chrono Stage they shot all 7 of 'em and I ended up with 164.7 Argghhhhhhh!

Very similar conditions and temperatures.

Black Magic, I guess... or bad luck

Rick,

FWIW, my loads averaged about 1.5 PF lower at Area 2 than at home on a ProChrono digital. it works out to be about 0.8% lower.

Later,

Chuck

[RePete]

I chronoed my loads on Thursday up at the main range (Area 2) with a ProChrono. 169 to 171 PF

It has always been pretty close to the CED's.

When I hit the Chrono Stage they shot all 7 of 'em and I ended up with 164.7 Argghhhhhhh!

Very similar conditions and temperatures.

Black Magic, I guess... or bad luck

That's why I like 175 - 180 for my PF. I make PF anywhere.

[Al Capizzo]

I' mentioned this before in the thread about Nationals, but Front Site recently had an article from Gregg Lent in which he said it wasn't uncommon for a load to read as much as 100 FPS slower in their chrono in a box than when shot over a chrono out of the box. Exactly my experience at Nationals.

My 172-173 PF loads (chrono'd several times) took 6 rounds, avg. highest 3, to make 165.4.

[double_pedro]

I' mentioned this before in the thread about Nationals, but Front Site recently had an article from Gregg Lent in which he said it wasn't uncommon for a load to read as much as 100 FPS slower in their chrono in a box than when shot over a chrono out of the box. Exactly my experience at Nationals.

My 172-173 PF loads (chrono'd several times) took 6 rounds, avg. highest 3, to make 165.4.

Not to let reality get in the way, but are match chrongraphs calibrated in any way prior to being dubbed (or during their use as) "official" chronographs? The same question goes for everyone's personal chronos as well. I can see it is not the easiest thing to do...you can't just whip out a handy velocity standard and measure it to see that you're getting the right answer. Alternatively, are several independent (different brand/model chrono) measurements used that are at least required to be consistent?

One thing I've thought about is that rather than using a box (with everything wide open inside), it may be better to chronograph using small aperature collimators over each detector so as to better define where (in the bullet's path) the time of flight measurements are being made. This may help eliminate aberrant results.

Edited November 17, 2008 by double_pedro

[XRe]

Not to let reality get in the way, but are match chrongraphs calibrated in any way prior to being dubbed (or during their use as) "official" chronographs?

Nope.

The same question goes for everyone's personal chronos as well.

Nope...

Alternatively, are several independent (different brand/model chrono) measurements used that are at least required to be consistent?

Nope...

These are just a small part of the reasons I feel that the chronograph (being worth roughly 10% of your match at any given match where a chrono is in use) is frankly kind of bogus - and its also why shred and I wrote the rule change proposal that in very large part became the new Appendix C2 in the latest rule book.

Until you can provide a "standard measure" and a method to calibrate each device - so that, given the same conditions, every device will read the same (or have a knowable offset to apply to it), you're at the mercy of differences in vendor designs and manufacturing tolerances. It can readily be demonstrated that manufacturing tolerances alone can make the difference between 170PF and 165PF (or below) - and it affects lighter, faster bullets to a greater degree than all others

In the end, chrono stations only catch the unlikely or unfortunate - they don't stop any cheating.

[gose]

Well, this one has me scratching my head a little bit. I'd worked up a load well before Nationals, chrono'd it a number of times and was easily making power factor with plenty to spare (172+). At Nationals I got 166.1pf...yikes! Today at Area-2 the exact same load...same batch of ammo actually, came in at 174.1pf. At Nationals, the bullet pulled was 115.4gr. Today it was 115.2gr. That means the difference in velocity was 72fps...

I know that doesn't help much, but I know why so many people talk about really low numbers at the Nationals....it happened to me and luckily I had enough margin built in. I'm sorta happy that today's numbers came back right at what I get at home so at least I know it's not that I have a crazy fast chronograph!

FWIW, before the Nationals I chrono'd 138.2 on my chrono (over 10 rounds), I did 138.1 at the Nationals and 138.4 at Area 2. All from the same batch of ammo. A friend loading on my press did 138.2 at the Nationals (using mixed brass vs me only using one headstamp)

I doubt I could even get that close if I did another three runs over my chrono...

[double_pedro]

Not to let reality get in the way, but are match chrongraphs calibrated in any way prior to being dubbed (or during their use as) "official" chronographs?

Nope.

The same question goes for everyone's personal chronos as well.

Nope...

Alternatively, are several independent (different brand/model chrono) measurements used that are at least required to be consistent?

Nope...

These are just a small part of the reasons I feel that the chronograph (being worth roughly 10% of your match at any given match where a chrono is in use) is frankly kind of bogus - and its also why shred and I wrote the rule change proposal that in very large part became the new Appendix C2 in the latest rule book.

Until you can provide a "standard measure" and a method to calibrate each device - so that, given the same conditions, every device will read the same (or have a knowable offset to apply to it), you're at the mercy of differences in vendor designs and manufacturing tolerances. It can readily be demonstrated that manufacturing tolerances alone can make the difference between 170PF and 165PF (or below) - and it affects lighter, faster bullets to a greater degree than all others

In the end, chrono stations only catch the unlikely or unfortunate - they don't stop any cheating.

I was afraid that was the case. It doesn't quite seem consistent with the "V" part of DVC making up one-thrid of the motto. I think a calibration/redundancy protocol could be set-up, but it would add some expense and complexity.

Thinking about this, it occurred to me that this would not be such as issue if the powers that be were to change the "all or nothing" approach that is built into the scoring system. I'm thinking about one where the competitors HF's are weighted by the ratio of their PF to the appropriate PF minimum but have a cut-off weight of 1. For example, if I am shooting major and I chrono at 165 or above, my HF's are what they are. If I chrono at say 160, then my HF's are reduced by a factor of 0.9696 (= 160/165). This could easily be built into EZ WIN Score. Seems like this would be worthwhile considering, if it hasn't already been considered. My $0.02.

Edited November 18, 2008 by double_pedro

[AlamoShooter]

my bulets ran 30fps slower at A2 than at home . same thing last year. it eat up all my fudg room and I ended up at 165.2

[ChuckS]

If I chrono at say 160, then my HF's are reduced by a factor of 0.9696 (= 160/165). This could easily be built into EZ WIN Score. Seems like this would be worthwhile considering, if it hasn't already been considered. My $0.02.

Why cheat yourself for A hits?