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Hot Topic (More than 10 Replies) On Chronographs (Read 9002 times)
joeb33050
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On Chronographs
Nov 24th, 2005 at 10:51am
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Looking for opinions here-do you have any left?
joe b.

On Chronographs
I'm starting to write the chapter on chronographs for the CBA cast bullet book. I've had a Pact chronograph for 15 or more years. I've used it to estimate BC by measuring velocity at 2 ranges, and used that estimate to calculate sight settings for 600 to 1000 yards before going to those long
ranges.
That is about the only use I've ever had for a chronograph.
If there are any things I know about my chronograph and shooting, they are: (normal range of velocities)

Variations in velocity have nothing to do with group size

Individual velocities have nothing to do with where the bullet hits.
Higher velocity than average bullets can hiot higher or lower or eastor west of the center of the group.

Standard deviations of velocity calculated to 2 decimals with n = 5 are statistically meaningless.
n must >/= 30, like it or not.

I've chronographed thousands of bullets, written down the velocities, done some statistics to these sets of velocities, and learned nothing.
I think a chronograph is a waste of money and time.
Comments welcome.
joe b.

From John Bischoff (he must be wrong!)
I only acquired my first Chrony a couple years ago. It gave me a window into what was really happening with my handloads. The various handbooks list x grains of y powder and a z grain bullet for w fps - but one never knows if one is actually GETTING what the books say. Then too, if one wants to use a non-standard powder (H4831 in 222 Rem with a 60 grain cast bullet) to achieve a gentler smoother acceleration, the Chrony lets one know how well the stuff is working (2375 fps, a small SD, and 2 MOA). 
One can use a chronograph judiciously to develop a load that is close to max with a powder for which there is minimal data, such as the surplus stuff available from GIBRASS and others. Or, one can verify that a moderate load with such powders really IS moderate.
I love chronographs.
John

  
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boats
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Re: On Chronographs
Reply #1 - Nov 24th, 2005 at 4:58pm
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Joe

We are of a like mind on the speed clocks.  It's good to know how fast your bullet is going but other than that not much meaningfull information is produced by all the calculations.

Thing that always struck me was the velocity is taken so close to the muzzle while I was intrested in performance 200 yards or more out.   

A bullet could leave the muzzle pretty consistent but according to many factors could be considerably different as it arrives at the target.  Those factors are mostly bullet related while the cronograph measures mostly ignition and burn factors. The least likely things to affect accuracy.

Boats
  
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dick_norton
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Re: On Chronographs
Reply #2 - Nov 24th, 2005 at 5:12pm
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Has anyone setup the chron. at 200 yards and tested our plain base lead bullets?

Dick
  
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PETE
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Re: On Chronographs
Reply #3 - Nov 24th, 2005 at 5:49pm
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  Well, for people who have their minds made up it's probably not much sense talking about it. But for those wanting to know a little about their usefulness, here goes.

  I think we can all agree that what Joe says about SD's to 2 places are not the best criteria. They are only a small part of what makes a good load. But I disagree that this figure is completely useless.

  I think we can all agree to that without a low SD/ES there is no possibilty of accuracy. The chronograph is useful in finding these loads.

   I think we can all agree that we have all shot those very small groups that can never be duplicated, yet we keep trying, proving that the definition of insanity is alive and well.  Grin

  A chronograph helps us separate out these factors, by showing us that that "fluke" group was just that by showing large SD/ES's. I have NEVER seen a load with an SD of 50 or 60 that would shoot well consistently, but have seen many loads under 10 that would.

  A chronograph is not a panacea, and like Boats says, it only gives the results of internal ballistics. But, you also have to remember without low SD/ES's at the muzzle there is no possibility you will get small groups at any range.

  Personally I feel a chronograph has saved me a tremendous amount of time and money by showing me immediately which loads might work and those that don't have a chance at all. Then further testing of the good loads over the chronograph will show me which of several will be best.

  The other side of the coin is to use Statistical Analysis, which if you followed that thread a while back, will show you that to reach a great deal of certainty you need to fire a great number of shots. A chronograph will show you in ten shots or less.

Dick,

  I haven't done any chronographing at 200 yds. but have done a little at 100 yds. while determining BC's. Will be doing so this Spring with the .40/65 and a friends .40/70.
  
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KWK
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Re: On Chronographs
Reply #4 - Nov 25th, 2005 at 3:06am
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An accurate chronograph gives you some clue as to the pressures being generated. A 2% shot to shot variation in fps usually means pressure is swinging about 10%.  If you're near the velocity limit for your cartridge, that sort of pressure swing is taking you 1/3 the way to a proof load. For me, that means it's time to look for a better combination of powder and primer.
  

Karl
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PETE
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Re: On Chronographs
Reply #5 - Nov 25th, 2005 at 9:35am
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  Here's a some more points to consider....

  We know that barrel vibration has a lot to do with accuracy. If the SD/ES's are to large then you'll get dispersion. So the closer you can get these figures, with accuracy, the less you'll have. This is very important the further out you go and I've read where Shilouette and Long Range shooters like to keep their SD's under 10. In Schuetzen I figure I want my SD's as close to 5 or under as I can get. In this way when you hit the right load the bullet will exit the barrel at very close to the same point in the vibration cycle. Preferably at the top or bottom of the swing where there will be a fraction of a seconds pause.

  Then we have the point about rifle ranges. It's pretty well established that you SHOULD do your load testing at the distances you want to shoot at. I will imagine everyone on here has easy access to at least a 100 yd. range or they wouldn't be shooting much at all. About five minutes for me to get to one. What about 200 yds.? They're kinda scarce. Mine is about 35 minutes away. Shilouette shooters need 500 meters, and LR shooters need up to 1000 yds. Now you're getting to where there are mighty few of them around. I'm lucky in that these are about 45 minutes away, but the last I heard you can't just go there anytime you want to. Only during match days.

  So.... A chronograph used at your local range will do two things. One, give you a muzzle and downrange velocity so you can figure BC, and with the MV you can plot trajectories and sight settings so you can be reasonably close to the target when you do get up there. And, of course, as mentioned previously, get you a selection of loads to try when you do get a chance to go.

  Then when we do get to that extended range we have to deal with wind and mirage. Unless you're a top wind & mirage reader.... which I'm not..... how do you know that the loads you're working up are really showing you what they can do? At least with the chronograph you'll have several loads to try that you know should work. Without an experts knowledge of wind & mirage reading, and how to apply it, you could spend a whole Summer trying to figure out which load MIGHT be the best.

  KWK,

Good points. Didn't think of that angle, but you're right!

  So Joe..... There's some opinions for you, but like a certain anatomical feature we all have, everyone has one...... Opinion that is!  Grin I don't expect this to change your mind, but might give some a better understanding of why a chronograph is not really necessary, but sure is a handy tool to have. I've had one, or another brand, for going on 40 yrs. and would say it's saved me their cost many times over.

PETE
« Last Edit: Nov 25th, 2005 at 9:45am by »  
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Jim_Borton
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Re: On Chronographs
Reply #6 - Nov 25th, 2005 at 11:37am
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You can not get a bc at 100yds and use it for 200yds because it isn`t the same! You lose about 3/4 of your 200yd vel. for 100yds to 200yds! Each yardage has it`s own BC.
Thingy Norton
Yes we are doing a lot of testing with the chono at 200yds, Barry Darr and I! And the things we have learn is unbelieveable! Barry has plans for a book if and when the testing ever ends. Our goal is to be able to send information out with each bullet mould we make!
And as far as  chono go if you think you allready know it all then you don`t need one. But I learn something everytime I shoot over mind. So when ever I shoot I shoot over my chono. It will tell you in a second if you had  a bad load or you miss read the wind or you just screwed up. What out a chono you will just keep making a same mistake over and over.
And what we have found out is "YES" Low SD and EP make for great group and accuracy. the lower you can get them the better.
  

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feather
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Re: On Chronographs
Reply #7 - Nov 25th, 2005 at 12:17pm
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John,

Before I got my chronograph, I considered my self a reloader.  I loaded what the books told me was a safe load and I shot it to see how accurate it might be.  When I got my chronograph, I felt that I had become a handloader because now I could get information that the books couldn't give me.  Are they really necessary?  I guess the answer to that question depends upon how much you want to learn.

feather
  
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PETE
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Re: On Chronographs
Reply #8 - Nov 25th, 2005 at 4:19pm
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Jim,

  You are right in that the BC varies as you go down range. It also varies with the muzzle and remaining velocity the further down range you go. BC is not a static thing and will vary with every 1 fps drop in velocity.

  But I have found that BC's calculated from a muzzle and 100 yd. reading will give you trajectories and sight settings very close. They will not be perfect as you suggest, but as I also mentioned, they will get you close enuf to the target to be useful when getting your final sight settings.

  Figuring out the sight settings for my .50/90 is a good example of this. After getting a BC, and using the MV, at 100 & 200 yds., settings gotten from a computer program were right on. At 300 yds. I had to go up a point. At 400 yds. it was right on again, and at 500 yds. I had to come down two points. I thought that was pretty good!

PETE
  
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MikeT
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Re: On Chronographs
Reply #9 - Nov 26th, 2005 at 11:11pm
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One other point about chronographs is that I have found different brand primers are not necessarily the same hardness.  When you have a velocity to compare various loads and now you are contemplating a slightly flatter primer with a given load; was it a higher pressurre load or a softer primer material, or both?   
keep on hav'n fun!
  
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PETE
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Re: On Chronographs
Reply #10 - Nov 27th, 2005 at 8:33am
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MikeT,

  Another good point!

  Different primers, and different lots within them, give different SD's. Schuetzen shooters seem to prefer Rem. 2 /12's, but in a lot of cast bullet instances this isn't so. Some loads I shoot require LR primers to show their best. Without the chronograph you'd never know this since the variations are small.

  In BP Shilouette shooting there seems to be a movement to the large pistol primer...... Quite a change from the "You gotta have mag. primers or you ain't in it!" attitude a few years back.

  A good accurate load is not decided by just one factor. It's a combination of all of them and a chronograph shows you which combinations work the best.

  I have read where the old timers could take as long as several years finding the best load for a rifle. Well, I've had a few stubborn ones that took a month a month or two, but mostly a coupla weeks of testing over a chronograph gets the best for me.

PETE
  
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Cat_Whisperer
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Re: On Chronographs
Reply #11 - Nov 29th, 2005 at 6:03am
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I do not have a chronograph - not within my desire to know exactly how fast a load is going.  (Although I did borrow one once.)

BUT, being a test engineer, and having had 6 or 7 graduate level courses in statistics, I know the value of instrumentation.

Simply knowing that the variation in velocity is large or small is good enough - especially in comparison to MY variability, when going for very small groups - control of both are necessary.  Measuring allows one to get that control.

Coupled with a strain gauge, one can develop highest speed loads with known pressures.

Do I get small groups, yes.  Can I do better, yes.  Do I persue it, obviously not.  Pennies as targets at 100 yards are OK, asprins are not.  Minute of beer-can accuracy is a more useful measure to me than MOA.





  

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dick_eesley
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Re: On Chronographs
Reply #12 - Feb 3rd, 2006 at 4:34pm
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thanks for your comments    I have come to the same conclusion regarding chrony readings predicting anything. my principal use is checking load speed as my ballard wants to be at 1440  dickeesley
  
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MartiniBelgian
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Re: On Chronographs
Reply #13 - Feb 4th, 2006 at 3:21am
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My main use is for BP shooting - I don't have the luxury of  longer ranges to do my load development, but I do like to shoot LR...  So I test my loads both for accuracy and MV at 100m.
When a load gives me :
- good group
- good ES
- high enough MV
I do consider that load good for LR shooting - without chrono, I was just guesstimating MV's (like from the rifle's recoil  Grin ), but now I KNOW where I am - that makes a lot of difference.
Another instance is shooting a .30-20 with a 150gr spire point bullet - try finding those in the loading manuals....

So yes, I do consider them quite useful indeed.  Now OTOH if you're shooting .22lr, you might go without...
  
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rimfire
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Re: On Chronographs
Reply #14 - Feb 4th, 2006 at 1:12pm
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I don't have a crono but I was shootin a 22lr match last fall - had a nice 10 shot group goin (just a frog hair over 1/2 MOA at 200yds) w/ a lite breeze right 2 left and had a shot go 3in high 4 no apparent reason - the only one of the group that varied more than 1/2" vertically - I would have liked to have a crono sittin in front of me that day just to give me a point to start ponderin from - instead of just sayin #*&@% ammo.

rimfire
  
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