Chronograph Blues!

[revbc]

Just got a new chrono.  It works great, but here's the rub.  The two pics below are from my 357 maxi and Ranch Dog cast bullets.  I shot three more sets with 1680, but this is the most pronounced issue.  The 3 touching had 129 ft per sec. difference between high and low, the other 3 triplicated the velocity 1946 ft per sec.!!!!  Go figure this out!  Know I know why someone said these things will make you pull your hair out!

Bobby

[mechanic]

Probably the best thing to do with that chrono is shoot it.  You're gonna' do it anyway sooner or later.  Then when you get those three touching, you'll feel great, and when the group spreads, you can blame it on heat or flinch or something.  I started weighing cases, bullets, and double weighing powder charges because of a chrony, and my groups didn't improve.  That leaves me or the gun................

Shoot the chrony....

Ben

[quickdtoo]

How far from the muzzle do you set the chrony? I set mine 13-15', too close and it will detect powder debris and muzzle blast whick can affect the readings.

Tim

[revbc]

Tim,

I didn't measure it, but guessing about 10' or more.  The other funny thing is on the 3 sets shot with 1680 the velocity consistently went down upon firing.  Looks like as the barrel heated up the velocity would increase.

The 3 touching in the pic, started at 2017 and ended at 1888 (going down consistently), if my memory is correct.  Didn't check my records.  The other 3 in the pic produced 1946 on each shot!

Maybe mechanic's right, SHOOT THE CHRONY.

[quickdtoo]

Well, there's an old saying, there are only two kinds of chrony owners, those that have shot their chrony and those that will. 

Richard posted a thread once on the distractions, complexities and general annoyances of reloading and shooting equipment, seems maybe you've experienced one of them!! Sometimes too much info can just confuse us!!  If you had just shot those rounds without the chrony, the first target would have put a smile on your face and the second you would have chocked up to barrel heat and there would be no puzzle to solve. 

Tim

[cwlongshot]

Tim right, too much useless information for the average guy...

Build a load, based of a edjucated guess of velocity and accuracy. Once a good load is found, chrono it to be sure your getting the "numbers" as in velocity you want. Then put it away. If not there, repeat the loadings and repeat...

CW

[bikerbeans]

Bobby,

Your chrony happen to be the little folding box type?  If so then it functions pretty much the same as mine.  I have found that like Tim says it needs to be a good ways form the muzzle of a rifle, expecially a 45-120.  At least 15' from a big bore.  I have blow the sun screen and shades off of my chrony just with the MZ blast.    The other problem I think is related to the sunshades the and sky.   Overcast with no sun shades works.  Blue sky with the sunshades works.  Mostly blue sky with scattered clouds and sunscreens, not so good.  I think that two or more exactly identical readings is usually the chrony failing to sense the next bullet.   You would have to look at the saved string data to verify that.  Also, the chrony is very sensitive to bullet height above the eye and the bullet needs to travel level and squarely over both the sensors.  I think CW is correct, get a good load and then just use the chrony to verify your velocity. 

Maybe Ben is right about the use of a chrony.  We could have the first & last annual GBO chrony shoot this summer?

BB

[keith44]

The best uses for a chronograph for me are (in no particular order)
1) interactive target
2) testing air rifle before and after servicing
3) final load development to make sure that over 10 shot average I am about where I should be with the velocity and therefore pressure.

Outside of that I leave it on the shelf

[gcrank1]

I don't use mine much, and when I do I run some 22LRs through it (well....through the screens) to make sure it is working. CW and BB are right ( as usual) from my experiences. It is another useful tool for me but I'm not going to get anal about it.
At long range that velocity variation would result in significant POI's, at the ranges you are likely to be using that rifle, no worries.

[goofyoldfart]

revbc: have you shot the chrony yet?

[AtlLaw]

Build a load, based of a educated guess of velocity and accuracy. Once a good load is found, chrono it to be sure your getting the "numbers" as in velocity you want. Then put it away. If not there, repeat the loadings and repeat...

Brie is absolutely correct!  He said it, I believe it, that's the way I should do it!     But I just can't!!      I have got to know how fast that bullet is going!!  My record sheet is built around velocities, spreads, max'es and min's, deviations and I don't know what all!   

I've tried to do it Brie's way...     Really I have...    Like when I need to work up a hunting load real quick... But even then I break out in a cold sweat every time a bullet is launched!     Half minute of angle load?  who cares!  HOW FAST IS IT GOING!?   

Tim right, too much useless information for the average guy...

But then, no one ever said I was average!      <or was it normal  >

[twoeighty]

revbc---been using a chrony for nearly 30 yrs working up load data for multiple guns/calibers----the only time i have gotten EXACTLY same readings was due to not sensing the next bullet---as stated in other responses, there are lots of variables(sunlight not properly diffused being the main one) but flight path over the sensors, muzzle blast etc can cause-misreadings-----i rec' to try the "EXACT" loading again at the same distance from the muzzle on an overcast day and see what you find

i've found that at high noon my readings get bizzare( 11am-1 pm)---so angle of sunlight does apparently have an effect as well

good luck with the chrony---280

ps> i just returned from a visit through the felicianas last week visiting my brother in Ethel, la.---record HOT weather---good to be back in boise, id. @50 degrees

[revbc]

Thanks for the input guys.  Twoeighty, I have some extended family over in the Ethel area.  Also have an old friend that pastors in the Boise area, Loren Yadon.  My wife and I spent about 5 yrs out west in California.  You're right, it has been hot and dry here.

Bobby

[dpe.ahoy]

My chrony is used to balance my shelf.   I let Richard worry about the speed, I just say it's fast enough if it hits the target and groups good.  Being a hunter and plinker and not a paper shooter, I don't fret over a fraction of an inch or 50 fps.  Life is good.   DP

[carbineman]

I think the Chrony is a good tool to make sure after checking for other pressure signs, one doesn't go overboard on velocity.

I was only able to attain book velocity a couple of times when working up loads in a Handi or Topper anyway, but I don't want to crowd my Toppers and end up wearing one of them.