Thread: Chronographs, what's the story

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

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

Originally Posted by Max Headroom

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

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

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.

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.
.

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?

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.

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.

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.

Originally Posted by Kscott

Same please.

++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?

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