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Old August 14, 2012, 02:55 PM   #1
browninghunter86
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Chronograph Help

I think I have a Beta Chrony I will be able to use next week. Few questions about chronographing.... I know to set it up 15 ft away and follow manuals set up but what about.....

1] Shoot at target for groups or not? Saw article online it says not to shoot for groups initail to do that next range trip out

2] Am I wanting low SD numbers the most and low ES numbers second? Read another article from a benchrest champion that he only looks at lowest SD to work with

3] 5 shots per group enough for usuable data?


4] Should I reshoot all loads or just the area I was getting my possible nodes?
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Old August 14, 2012, 03:27 PM   #2
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Heres what I do, others will vary.

Shoot at a target?
Yes, it's both cheap insurance to have a specific aiming point so you're less likley to hose a screen, & it gives a basic idea of how the load is performing. Just low numbers may not equate to actual accuracy.

SD & ES numbers.
Ideally you want low SD, meaning each shot is closer to it's neighbors, but odd "outliers" will cause the ES to open up. Your aim is consistency shot to shot so I go for SD, but if I get a wide ES then I have a problem with outliers.

5 Vs 10 shot strings.
5 shots is enough, but the more you fire the more representative your data will be in reality instead of in thoery. You can test this easily. take 15 identical loads. Fire a 5-shot string & note the data. Now fire a 10-shot one & compare the 2 results.

I only reshoot if I get contradictory data or unbelievable data, or re work something in the load.
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Old August 14, 2012, 04:13 PM   #3
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I always use a target when I'm setting up a chronograph, as I prefer to test for group size at the same time I'm checking velocity. As wogpotter said, it also helps alot to refrain from hitting the chrono by mistake.

5 shot strings are OK, but 10 is better, both for velocity and group size. One thing to keep in mind is that if you're testing an auto, it's not unusual for the first round out of the magazine to print slightly differently from the others which can affect group size. I believe it's due to how the gun goes back into battery after the first shot, but that's just my guess.

As far as focusing on ES or SD in determining the best load, I honestly have to say that I've seldom found a direct correlation between either of them and the smallest group size.

As far as re-testing goes, I usually retest the 2-3 best loads at least 2 more times, even over different days, and then compare all those results. Sometimes, it's surprising how a temperature or humidity change can alter the chrono results slightly. It usually doesn't alter what was the best performing load though.
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Old August 14, 2012, 04:30 PM   #4
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SD isn't really meaningful unless at least 10 shots have been fired. More is always better of course. My minimum is 15, max is around 30. BTW you can almost count on your SD being approximately 1/3 of your ES. Note that with more shots you can eye-ball the data and be more confident of them. If one reading is way out from the others you can toss it and still have a meaningful string. Accuracy is of course #1, ES is #2 in importance, SD being 'interesting'. Average velocity is nice to know too . Remember the more ES, the more your bullets will hit differently on target. Not so much at 15Y.... but more significant at long distance shooting. I strive to find loads that are under 50 ES. Over 100 is not acceptable at all.

If you read your manual, they suggest shooting 4-6" over the chronograph. I put black tape on my guides so I know about where I should be shooting. I do put a target downrange and shoot for groups (benchrest). Takes a bit of time to get everything lined up from bench, through chronograph and on target. Helps to have a adjustable tripod for the chronograph (lots of trips back and forth to get it 'perfect'). Once set though, you are good to go. I change targets for each load test. If you get errors or fast reads (says 1400, when the others have been ~900), move the chronograph a bit further out. Sometimes that helps.

Promising loads, I'll shoot again later without the chronograph to retest for accuracy.... just to see!

Hope that helps a little bit.

Note I shoot mostly revolver ... not rifle. Seems the rifle shooters don't shoot as many test cases.... I hear 2,3,5 at most .
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Old August 14, 2012, 08:24 PM   #5
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I use the chrono to find the lowest es and sd, then remove it and shoot for groups. You don't want any distractions while shooting groups.

No coffee or beer the night before. Heartbeat in the reticle is a pain and those make it much worse.

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Old August 14, 2012, 08:35 PM   #6
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I wish I could find the link again. If I do I will post it he only loads and finds the charge velocity range he is wanting and with lowest SD and that all he looks at for his loads.
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Old August 15, 2012, 10:49 AM   #7
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do you think SD or ES is more important to have lower?
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Old August 15, 2012, 12:30 PM   #8
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Both as I posted earlier, but if you have to pick one & ignore the other I'd go with SD.
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Old August 15, 2012, 03:14 PM   #9
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If you have the ES, you might as well compute the SD or visa-versa. But, I personally feel the ES is more important as the more velocity difference, the more POI is going to be changed... I've tested a lot of loads and you can just about bet on the SD being ~1/3 of the ES anyway.... The tighter your ES, the tighter your SD is going to be. Here are a part of one of my test tables as an example:

SD,ES,shots
18,55,17
17,59,20
19,62,20
13,44,13
17,58,36
12,42,12
25,81,16
10,30,15
13,45,30
5,15,13
8,32,15
8,27,15
7,23,15
31,118,28
8,30,15
12,33,14
10,38,14
28,115,30
...
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Old August 15, 2012, 04:29 PM   #10
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I use the chrono while doing OCW load development- which is 3 shot groups.
Certainly makes sense to use it while doing whatever type of load development you do...

I do think some guys get too carried away with velocity. Velocity is always a plus- but if it comes at the expense of accuracy, it's of no benefit. Very rarely has max load provided me with max accuracy.
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Old August 16, 2012, 04:07 PM   #11
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I certainly shoot over the chronograph at targets during load development. I do single shot ladder testing to start load development and I simultaneously plot a graph showing velocity for each small charge change as each load gets progressively hotter. It's been easy to see speeds becoming more consistant as pressure climbs up to the proper level and produces a more consistant burn rate. Velocities will begin to fluctuate again as pressure gets passed the normal safe area. IME, max velocity and lowest velocity variation generally comes when the loading density is around 90-100% in the max pressure range but accuracy may be poor even if the SD is single digit. Contrary to 'conventional wisdom', best accuracy is NOT directly connected to lowest ES/SD but if accuracy is poor when the statistics are good you'll need to try another powder.

To get an idea of the effect chance variability has on statistics based on small sample groups try this; fire 20 rounds of your favorite load over your chronograph and list the speed of each round. Then pick the three (or five) closest together and widest apart; look at the ES and SD of the worst and best groups and know that either group could be what random chance might produce if you tried to base your presumptions on those particular small examples of the same rounds. I know of nothing you can do that will better demonstrate the hopelessness of trying to use small sample groups as a statistical base.

Last edited by wncchester; August 16, 2012 at 04:13 PM.
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Old August 16, 2012, 07:57 PM   #12
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Quote:
Contrary to 'conventional wisdom', best accuracy is NOT directly connected to lowest ES/SD but if accuracy is poor when the statistics are good you'll need to try another powder.
True. But you certainly have a better chance if your shots are consistent! I've yet to find a load that has a high ES that shoots very well .....
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Old August 16, 2012, 08:13 PM   #13
browninghunter86
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another forum said his best accuracy was with ES of 130+. Don't see how

I have def learned more than I thought I needed over the last few days on here and researching on the internet.

Thanks to everyone who has helped out with information
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Old August 17, 2012, 12:19 AM   #14
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Low es = consistency.

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Old August 17, 2012, 06:29 AM   #15
browninghunter86
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and consistancy is your friend in reloading
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Old August 17, 2012, 07:31 AM   #16
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While SD & ES are part of the story they aren't the whole story. For example it's possible to get very low ES & SD, but with horrible barrel harmonics. This give poor accuracy with consitent velocity.

A chronograph measures speed & performs statistical calculations, nothing else.
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Old August 17, 2012, 12:24 PM   #17
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^^^^
This.

Velocity, and consistency are completely irrelevant if they do not produce accuracy.

Too much concern with stuff that may be relevant, but often is not.

It all boils down to how close you can put the little holes if we're talking precision shooting. Tiny variations in load results pale when it comes to barrel harmonics.

This is patently obvious when you consider that you can take the most accurate load from any factory rifle you choose- shoot it from the same model rifle and get completely different results.
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Old August 17, 2012, 03:03 PM   #18
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Before someone gets their knickers in a twist.
I'm not saying a chronograph isn't a usefull tool, I have one & use it a lot. My point was that you should be looking for both good barrel harmonics and good consistent velocities. I was trying to clarify the part about why consistent velocity isn't always indicative of good accuracy.
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Old August 17, 2012, 03:24 PM   #19
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good info. Find good barrel harmonics and accuracy then use chrono to help understand how your reloads are behaving and make drop charts
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Old September 10, 2012, 11:44 PM   #20
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Magnetospeed has caught my eye and been doing some research online and seems it is just as accurate as the more expensive chronys out there and alot easier to set up and use

Anyone use one of these units?
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Old September 11, 2012, 01:28 AM   #21
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Seems a but pricy compared to a chrony, but more importantly, what does that do to barrel harmonics? Can you attach to barrels with a front sight or a tube Mag like a lever gun?
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Old September 11, 2012, 08:38 AM   #22
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Quote:
Magnetospeed has caught my eye and been doing some research online and seems it is just as accurate as the more expensive chronys out there and alot easier to set up and use

Anyone use one of these units?
I ordered one and it should be here by the end of the week and I should be able to test drive it this weekend. I'll post something after I try it out.
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Old September 11, 2012, 10:51 AM   #23
browninghunter86
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1stmar: alot of info on accurateshooter about it affecting harmonics and it appears to change slightly. Most reported it move POI up ever so slightly when it is used.

here is my personal thought: me spending $100 for cheap chrono, then a tripod, then a laser bore sighter to make sure everything is set up perfect, I am right there at Magnetospeed price point. Then if using a more expensive chronograph add atleast $100 more then I am actually saving money for a unit that is foolproof and requires very little set-up and don't have to adjust tripod if you shoot a different position or worry about lighting or clouds
***From reading it appears it gives about 1% higher velocity reading than say CED 2 or the O35 unit but I believe that is due to those being set at 15' and this is at the muzzle.***

Bumnote: awesome. Do you have anything to shoot inline with to compare the data?
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Old September 11, 2012, 05:52 PM   #24
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As long as you separate activities (shooting for groups and chrono graphing) it looks like a good solution. I don't separate as I like to understand if there is a correlation between velocity, group size and poi. Interested to hear how you like it.
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Old September 11, 2012, 06:25 PM   #25
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+1
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