49 replies to this topic

[rich]

One reason why all chrono testing should be done in an alignment jig that holds the barrel axis concentric with the chrono axis and the muzzle at a constant distance from the entrance. It's easy to incorporate a blast screen too.

[daz ford]

one thing that does vary the shot string results is the angle at which its fired through the chrono, if the angle changes so does the reading.



Which is why at the beginning of chronoing at national shoots there was a jig at the front to align the barrel/rifle to the chrono.




Regards


Daz

[daz ford]

Gary, not digging at you mate.

maybe this jig needs to be re-evaluated ?

Or thier needs to be a designated BFTA official at the chrono at all times to do the testing ?

Or maybe a completly mobile 'dark room' for the chrono to live in which will be a controlled enviroment ?( back of a van/promo vehicle)



Just my(and some others today at sdftc) idea's.


As we all know, the BFTA are damned if they do and damned if they don't.



Regards


Daz

[rich]

Ahem, at our club we have a selection of jigs, one for each common type of construction, so it is possible to find the one that fits the best.

The jigs are made out of softwood timber and a handful of screws. I doubt they would cost a fiver even if you went out to buy the wood because you didn't have any offcuts to use up.

I'm sure I've posted this pic before http://i214.photobuc...P1000288low.jpg

You can see the vee blocks that carry the SKAN, the vees that carry the reservoir, the square notch cut out for a stripper or muzzle brake, and the blast screen that doubles up to prevent the chrono from being shot.

[holly]

Make you right berty . run my rifle at 765 . it seems it it is mostly coming from the shooters who run theirs to close to the limit ??? HOLLY

[RN10]

What % of the shooters at a GPs does this effect or is it people who try to run right at the limit as I have always run my rifles at round the 11lb mark with what ever pellet I am using and have set the turret up to this setting and have never had and I do not have clue what the chrono make was at Kent Woodsman on Sunday as it was in the wood with no cover over it and my 2002 was 778 which is the same as my PM1 and if you get the chronoing removed I would still do the same. What next the chrono has to be in the correct line with the rotation of the earth other wise the chrono may getting closer to the barrel end after you have pulled the trigger if this was not set right. Keith.

[Flannelmeister]

In the morning, before shooting the afternoon session at Nelson, I checked my gun over the chrono and it came out at 822fps with mozzies which I felt was a bit close. So, I turned it down and re-chronoed it @ 814fps.

I started on lane 21 so only shot 10 targets before facing the chrono again during shoot ant 1st shot was 824fps! Luckily 2nd shot was 819fps so was ok to continue.

No idea if that was chronograph inconsistency or a light pellet, but sometimes you try to do right thing and it just don't happen.

[rich]

All these responses seem to take the view that the chrono won't be that far out so if we keep the guns 30 fps or so below the limit then we have a comfortable safety margin.

Let me ask a simple question. Please justify why you are confident that the chrono will only be out by a small amount. And now here are two more questions: if there are two chronos that read differently, which one do you trust, and why?

Before anyone kicks off, remember I have clearly stated I am in favour of all measures to prevent cheating and that includes reliable checks with a chrono that actually have some value.

[Jon]

Well Rich i dont trust either nearly always up 16ft/sec on 8 other known chronos. In fact i have only once seen it give a satisfactory reading in 4 years.
What do you call too close? As said before i know of people running at least 25ft/sec faster set on same chrono and still passing the BFTA one, thats what you call fair.
Have seen the chrono several times give readings in the region of 844 with a multitude of guns and locations. Its not a case of setting 25 to 30 ft/sec under, need to be 70 ft/sec+ under BFTA limit due to being legislated with a dodgy chrono and testing procedure taken as gospel.

[mikewills8904]

well i checked my domi in the morning at gp8 when i heard a few people say they were reading high

mine read 784 with jsb

shot pm and chrono read 788

i set mine at 780

still shot like an -bottom- though

[Piemanlarger]

As for GP8, we did try to make sure that the chrono was under cover, the PM the sunlight did come directly down onto the chrono. But out of 79 shooters only a few were told they were over the limit? If it was a constant problem then more would have been removed from the line? I like to keep my guns well under the limit to make sure they go through every time.

And thats my point, were those who were "over" actually over or was the chrono in direct sunlight giving false readings??

For my gun to register 835 (which would be about 845 on our club chrono when set up for 810) and then 819, i cant help but think the chrono reading was "faulty" due to the sun.
God knows if i had been shooting at 835 i would not have needed to come off the plate for wind

Anyway, hopefully at gp9 the sun wont be out!

[mikewills8904]

there seem to be a few readings that are not quite right i know johns gun was reading up on power
on the gp 8 chrono

i think that chronos are a must but if the are not accurate then that aint no good

i know we can set our guns at lower power .but are we not fixing the wrong problem

it aint that hard to put the chrono in a enlosed tent to avoid direct sunlight

[wilam]

Ballistic pendulum!

Might be the answer, they are not as 'readout' precise as the digital ones.
But all you actually need is pass or fail, which it will do with ease.
Gerald Cardew used one and he knew a thing or two.

[holly]

Pie Man . don't like to disillusion you but from my FAC days you would need 850 and up to make any real difference and really about a thousand FPS to be assured of very little wind out to 50 yards . YES wilam . they are a little crude . but they are simple . cheap , very easy to set up . and cannot be effected by the changing conditions . anybody got one of mr cardews pedulums . obviously it would have to be an update . say put in a clear plastic box . with a tube down which the pellet would fly . no splash back . no damaged chrono . NO MOANS ??? HOLLY PS how about the BFTA approaching mr bowket for a design . now there is a man who knows his Ps&Qs .

Edited by holly, 18 August 2009 - 10:52 AM.

[rich]

Agree with Holly. 50 fps makes very little difference to the wind aim-off, there's more to be gained by judging the wind speed and direction with better accuracy.

[neale m]

I set my Walther to 775 for JSB's also 775 for the EV2 that leaves plenty of Le-way for discrepancies

1) Light Pellet
2) Pellet with lube
3) Gun (ie:- shrouded - muzzle - silencer - barrel to far or to close to the sense)
4) Weather
5) Chrono
6) Pilot Error

and I'm still legal

[holly]

Plus of course as neale says he is legal and he would still be legal if his rifle was tested with a heavier pellet . which could come . HOLLY