Chronographs, what's the story

Yesterday I shot some new powder for groups, chrony readings reasonably steady, I mean not to much variation, sorted out a couple of loads that looked interesting and took them back today for a recheck.
Same load , same sort of grouping but readings near 100FPS faster the readings were as reasonably steady as yesterday.

Had the sun shields on both days, sun not out as much yesterday, but still there, but bright today,
then clould cover came over and the speed dropped 50-80-fps for the same grn weight.

Drives me nuts, anybody got a solution.

Validate at distance is the only solution I got, it's a real piss off as it happens to me every time I go out and not willing to spend big bucks on a flash chrony...

Your right, thats the only true way, but it just drives me fuken nuts cause it happens time and time again, you think you have it sorted, then bugger the damn things are supposedly going faster.:D

Glad I'm not the only one that doubts the chronograph ha ha

Now you know why I got an Oehler

You still need to validate at distances but at least I know the speeds are about right.

Shame about the $$$ not worth it unless you are doing heaps.

These sonic things, anyone have an opinion about them yet?

I only trust it when it's sunny. The numbers from clear, bright sunlight seem to line up at long range.

What brands are you guys using? I use a Competition Electronics one, it seems to be more reliable than my friends shooting chrony (the Canadian made ones). The numbers seem to stack up at distance, and it's never thrown a hissy fit on me.

F1 shooting chrony

Shooting F1

it's been shot, hit with fragments from an exploding suppressor, and still works

it just needs bright light to be accurate

i have got an oelher and a pro chrono which reads to with in 4fps of the oelher so mainly use the prochrono and then verify by shooting

should look at getting a magnetospeed v2 chrony dude . or getting a bunch of mates together and putting in for one , accurate as , so easy and fast to set up and not affected by light. well worth the cash rather than struggling through life on the conventional chronys wondering wtf is going on and then end up shooting it haha

Jakewire I know bugger all about this stuff but a question occurs to me and that is "could the difference in speed be explained by the difference in temperature of the powder in the rounds on the two days"? A test would be to take ten rounds from the same load, put five in the fridge over night and leave five out. On the next day run the five from the fridge through the chrony from straight out of the fridge ( or chilly bin if you have to transport to the range - i.e. no time to come up to the ambient temperature) and then put the other five through the chrony. If there is a dramatic difference in the fps readings between the two groups then the powder burn is likely to be sensitive to its temperature at ignition and will possibly explain the difference in speed on any two given days.

Just a lay mans hypothesis.

I only use my f1 comparatively.
Ie shoot a known load that has been over Gregs ohler and validated at range and if its say fast 80fps subtract that from the load in question.
Gets pretty close.

The Magnetto speed ones are great, but shooting groups with it on can be a lottery esp with a light weight sporter barrel.

Are you throwing the powder charges or weighing/trickling individually?

Using mainly adi powder Rushy which is supposed to be pretty stable.
perhaps if I had left a rd in the hot chamber to long before firing, then I could put down an individual 80 odd fps to that
however these were consistant but consistantly higher/ Lower.
Having said that, in this particular case I was using N560

As perhaps in the last of the 30 06 thread , maybe it's just my crony is just not particuarly accurate.
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Rainy day project: improve the F1 maybe? The reliance on natural light for the Chrony and the resulting inconsistency has been quite a problem for me (and the cost of 9V batteries). You could try repackaging the guts of it to be covered on both sides and an oversized top so there is no chance of sun shining on the sensor apertures and keeps the rain off, illuminate the sensors instead with a row of LEDs above each, run it (and the LEDs) off 8x AA rechargeables. Works a treat, rain, shine, light or dark. I'll take a pic and post next time I have it out. Maintain exactly 12" between centres for the sensors as in the original, same for the LEDs, to keep the calibration.

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Originally Posted by Puffin

Rainy day project: improve the F1 maybe? The reliance on natural light for the Chrony and the resulting inconsistency has been quite a problem for me (and the cost of 9V batteries). You could try repackaging the guts of it to be covered on both sides and an oversized top so there is no chance of sun shining on the sensor apertures and keeps the rain off, illuminate the sensors instead with a row of LEDs above each, run it (and the LEDs) off 8x AA rechargeables. Works a treat, rain, shine, light or dark. I'll take a pic and post next time I have it out. Maintain exactly 12" between centres for the sensors as in the original, same for the LEDs, to keep the calibration.

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Yes please, post up a pic when you can. I need to do something like this to my F1 as it does my head in too.

kj

Same please.

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Originally Posted by Kscott

Same please.

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++1

I've been thinking about building a plywood box to encase mine in ...


Tim

How much light do you need to provide via the LED's? Can you have too much?

Attachment 18239Attachment 18240Attachment 18241Attachment 18242Attachment 18237

As can be seen the conversion was mainly a mechanical one. Electrically the Chrony circuit has an on-board 5V regulator so either 6 or 8 cells should be fine. Operating time between charges is set by the current run through the LEDs as the chrony circuit itself doesn't draw much.

On the question of brightness I'm currently running 10mA through each LED and I have 20 in a row to get that light-bar effect, all in parallel, so 200mA through the LEDs - the front & back strips are then run in series. 8-10 hour run time. The LEDs came from Jaycar Electronics as some sort of pre-made strip lighting that can be cut to length off a reel. I had 2-3 metres of it and that gave me 60-80 LEDs. The tricky bit is that these then need to be removed and rearranged side-by-side on your own bit of circuit board with their own series resistor each to make a pair of 55mm wide solid strips. They are Surface mount style so this will test your soldering skills. Once done it does work really well and doesn't miss a beat. Less forgiving than the plastic screen if it took a hit though.

Looks good, thanks for the ideas

Close up of the small strip of printed circuit board with the LEDs on it.

Attachment 18266

Wildman that may be right, it may be possible to have too much light. I vaguely recall that cranking the LEDs up took the sensor circuitry out of it's designed operating range - a bit like trying to get them to work with direct sunlight. The LEDs on this one have a voltage regulator between them and the batteries so the light intensity can be adjusted. Feel free to PM if you like for other details.

Cheers, ta.

hi all
yeah, I know its an old thread but with recent experience and not seeing mention of my take on it....
l've found I need to take care on aligning the chrony parallel with the shot, one end higher than the other shortens the bullet path, hence higher (different) numbers.

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Originally Posted by gimp

Shooting F1

it's been shot, hit with fragments from an exploding suppressor, and still works

it just needs bright light to be accurate

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My 338 Lapua blast blew the front off my F1 and rolled it around a tad I managed to fit it back together still working but I use a Magnetospeed now seems simpler but it has affected my grouping and point of impact.

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Originally Posted by xtightg

My 338 Lapua blast blew the front off my F1 and rolled it around a tad I managed to fit it back together still working but I use a Magnetospeed now seems simpler but it has affected my grouping and point of impact.

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I modified mine with a 480gr round ball at 1200fps. Rolled the bugger in the dirt too... On comparison to all my previous loads, it's still spot on and I still use it. Attachment 127338Attachment 127339

still works?

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Originally Posted by outlander

I modified mine with a 480gr round ball at 1200fps. Rolled the bugger in the dirt too... On comparison to all my previous loads, it's still spot on and I still use it. Attachment 127338Attachment 127339

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I bet when that happened the numbers disappeared off the display, and "OWW, YOU BASTARD" flashed on instead

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Originally Posted by Awaian

still works?

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Sure does. Amazing as it still reads consistent to my loads.

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Originally Posted by Max Headroom

I bet when that happened the numbers disappeared off the display, and "OWW, YOU BASTARD" flashed on instead

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'Lift the barrel a tad ya prick' also. Cheeky things chronys.

Had a Steinert Superchronograph and it worked well regardless of the light conditions as it's sonic based. A little fiddly setting it up as both ends of the chrono must be dead parallel to the bullets path. Now use a Labradar which is easy to set up.

I have an old Canadian CHRONY F that is free to anyone that wants to pick it up. Just needs a 9v battery. Live 100m from SH1, Tokoroa.