I am soliciting general tips and advice on chronograph use and interpreting the data collected.
From some of the old posts:
1. minimum of 10 rounds for StdDev accuracy
2. use new cases ( is using 1x and 2x fired brass a waste of time?)
3. hand weigh each load
4. shoot ten rounds of 22 over the chrono to test setup?
5. ?
6. ?

I am particularly interested in what the data tells and how to grade the quality of particular load.
In different threads, members have done this with statements such as:
• they like to see SD below 20
• ES is good at 7-8% of average velocity

Personally, I think accuracy/grouping trumps chrono results, but I spend quite a bit of time prepping cases and measuring everything as I reload - so it only makes sense to me to get a little more info other than the targets to help learn about this craft.

Are there any good references out there? books, articles, software, etc
I've taken many college math courses, but statistics wasn't one of them.

thanks in advance

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I'd like to agree with you BUT

JMHO

I think too much is placed on Chrono readings. I use it to give me a general idea of what my loads are doing.
Other than that it is what it is.

For general range shooters the data is less important than big time Match shooters where everything matters!
"How many Angels can dance on the head of a pin"

A few 22 lr to see if the chrono is reading but that in itself means what? It is from the box of ammo that says 1200 fps out of what ? Probably a rifle.

No, you do not need to use only new cases. Same headstamp is fine. Yes, weigh the powder.. At least 10 shots.

I do like to see low SD and low ES. Others do not .

As with any statistics, the larger the sample the better.

Everything matters, heat, humidity, gun, etc etc.

One of our members here is a Statistics man, hope he chimes in.

I never use a target when testing with a chrono. All I want is data, I take a bunch of test loads and just record result.

Testing for accuracy is a different step without the chrono in the way.

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Still Running Against the Wind

I do clock my test loads while shooting them at a target. I don't see how the chronograph can be "in the way" unless it is in the line of fire.

I always prefer to see small deviation numbers but have become less obsessed with them. I have two rifles that shoot one-ragged-hole 100-yard groups with numbers that suggest the recipes should deliver poor accuracy. But if any load does shoot poorly with good numbers, I feel it deserves a retest as shooter error could have been at fault.

Ed

I really pay no attention to the std dev. It's kind of like shooting groups and not counting "fliers" in my opinion. The two numbers that I pay closest attention to are the average and the extreme spread. Loads with excessive ES don't get kept, even if the std dev was ok. I like to see loads with 5% or less ES, although in my opinion, any single digit ES percentage is ok. 10%+ ES means something about the load isn't quite right and it can get tweaked.

Responding to your points:
#1 is good
#2 I do sometimes but not often, I usually want to know what my actual reloads are doing, not the best case scenario.
#3 I make a point of weighing enough to get a feel for the charge, but I specifically do not trickle charges anymore. Once again, I want to know what the actual reloads will do, not the best case scenario.
#4 I don't have a .22 but I know die hards will shoot a load they know to make sure the chrono is "on."

Just saying I do not care where the bullet hits a target if all I want is how fast it goes.
I concentrated on kicking it through the uprights, left or right doesn't matter to me

When testing I also use a rest

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Still Running Against the Wind

I need one known round over the screens te determine it's working right, 10rds, waisting ammo IMO.
Set the screens the same distance form the bench everytime, I like 12ft min for handguns, 15ft for rifles.
Testing is testing, unless you only shoot 1x fired brass, why only test that way?
Interpretation is dependant on what you are trying to learn. LOW SD is nice, but means little if the load won't group well. You are right, accuracy trumps low SD. I like to use my chrono to show changes in a given load. All things being equal, vel increase often means pressure increase. So if switching primers, cases, OAL, etc shows a vel increase, I am getting some pressure increase as well.

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NRA Cert. Inst. IDPA CSO

Rule
I am not sure where chrono testing is going to take me - but I'll do it for awhile - I think it'll help me understand more of all that's going on - as for the 22 - I read it on an old post here - I shoot CCI std vel 1080 fps out of my Victor so far all the 22 readings have been around 980 fps - heck Victor goes to the range everytime anyway - today was my 4th time out with the chrono - I'm seeing that I probably don't need to do the 22 shoot each time
good to hear about not needing new cases - but I think I read that in one of Skip's old posts
what's a low ES? low SD? >10, >20 ???? and what's high?

Avg Ed - I have been shooting at targets - but I'm shooting 1 round into its own target- 5 targets on one 8 1/2" x 11" paper - and keeping track which chamber it comes out of - I'm curious how each POI is with each velocity. but I am watching that I don't shoot the chrono too - so I'm a little distracted and it may show up in the groups


waywatcher - thanks - good point about actual reloads - instead of best case scenario - I can see starting out using high quality, time consuming reloads and then later testing - higher quantity production rounds - using the powder measure, etc
thanks for the percentages

Rule - I am spending so much time loading these rounds - I want the max info out of the testing - I can see as I get more experience loading and understanding all that's going on, including the chrono data - I'll probably just shoot for the stats

fred - one round? just the velocity of the load? I'm guessing you are comparing that one velocity to previous chrono tests, which makes sense if you've built up a database prior - other than that I am curious what you're getting from the one shot

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I'd like to agree with you BUT

Some stuff I've learned - hope it helps:

- There is no way to calibrate a chronograph - you simply do not have an object of truly known velocity to compare it to. And if you did, you don't have a way to adjust the chronograph.

- Firing 22LR is not very valuable - what (if anything) produced the velocity printed on the box? While useful for a less expensive "is it turned on, lined up, operating?" or "are measurements reasonable and consistent?" type test, you can do the same with your own ammo.

- The more data, the more statistically valid the conclusion. OTOH, if you fire a group of 5 and the ES is (eg) 15 . . . those 5 had pretty consistent velocities

- ALl chronos require setup, and one or more early shots may not be recorded. So its best to come prepared with "setup ammo". Also keep in mind that your standard optical chrono will periodically fail to record a shot due to light changes, wind, etc.

- Chronos measure the velocity of whatever you shoot across them. Doesn't matter whether the brass is new or used, it measures THAT stuff. How you apply the data to future loads is up to you. OTOH, if you measure fired and neck-sized ammo from the same rifle, you likely have minimized one of the variables that could contribute to variance from future reloads.

- At some point you (or a former best friend) will shoot your chrono. This is the only unconditional guarantee that comes with every optical chrono

I'll share my practices on chono use.

Set up:
- I always set the first screen 15 feet from my rifle muzzle (have a marked cord to make it easy)
- I replaced my metal rods with ones made of wood, so if/when I shoot one only the wood rod needs to be replaced.
- I marked the 4" to 6" position on my wood rods with bright tape. This is my area I want to keep the bullets going through.
- I use a cheap Bushnell laser bore sighter to set up the chrono. I have the rifle in a rest and put one of the safety flags in the chamber when I have the bore sighter in the barrel. Just helps me know the exact path the bullet will take. (Obviously I have the rifle in the rest sighted in the center of my targets when I start).
- I always use the diffusers since I always have a clear blue sky.
- I use a bubble level to adjust the tripod so the chrono is level.

Use:
- I am shooting groups when I use my chrono. The chrono just collects data for me as I evaluate loads. My view is that I am less likely to shoot the chrono if I am using a target as a consistent aiming point.
- Knowing the velocity is very useful to me to understand pressure. I know it isn't perfect, but it is another piece of data for me to utilize.
- Most of my loads are based on QuickLoad calculations verified as best I can with load data from manual. But rarely can you find the powder and exact bullet I am using, let alone seating depth. And I know my chamber, powder lot, altitude, and humidity are different. And usually the primer, brass, barrel length, temp. etc. may be different. So knowing velocity helps me establish where I am.
- I don't fire over mine with a .22 or other established load. I have enough confidence that the chrono will give me accurate readings within it's ability.
- I'm not trying to come up with the hottest loads, I am trying to find the loads that perform the way I want. And without knowing the velocity, you are missing one of the key variables.
- When I change a significant variable such as powder lot, I can adjust my powder charge to get me to the same point due to the differences in the burn rate of the old and new powder lots by knowing velocity.

Like you already mentioned, grouping/accuracy rules over SD.

TO verify the chrono is setup properly. If you know the vel from your test round, it only takes one to determine the setup. WHy I said, from a known round. Continuing to shoot known ammo over the screens outing after outing is telling you nothing.

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NRA Cert. Inst. IDPA CSO

I used to fire 10 rounds of .22 Super-X at the beginning of each session to use as a baseline of chrono performance. When that ammo ran out I bought a brick of some other brand to use. The PACT chrono was sensitive to battery power level and by shooting a known ammo (sometimes at the end of a session too) I could estimate if my other readings would be good or trash due to a worn down battery. With my current chrono I don't have to do that but every once in a while I do just to check I'm getting expected results.

Another thing a chrono will let you know is how fast the same loads perform in different guns. Often you will find one gun shoots everything a little faster than the other horses in the stable. Other times it will be all mixed up, which leads to interesting speculation on forums such as this. Great for your free time. (the chrony made me do it honey, be there in a moment).

Since I still have a pretty easy time of shooting thru the chrono screens at 10' while looking at a target down range at the same time, I almost always test for group size and just record the chrono data for what it is. It DOES take a bit of setup time to get everything aligned in the first place, so this is not usually convenient at a public range and I can see why some would rather separate the speed tests from the accuracy reviews but then you won't know if that flyer was outside the normal load or not.

Like was said, use the same components and methods as you normally load. Only time to make something special is when your testing that special thing.

I put some little velcro tape attachments on the side of my screen supports and then stick a piece of zombie green surveyors tape across it about 2" or 3" above my sensors - that way if I see the green flagging I know I am aiming too low and might hit something.

Guns and computers are complimentary like bread and butter. Those of us that use them both are typically engineering types that are always asking the question...why?. With the use of a spreadsheet and some computations you can refine the basic data from your chrony AND with On-Target software analyze your groups.

I need to say right now that even though I did sleep at a Holiday Inn Express last week, I don't understand statistics very well. There are several here that can poke my statements full of holes, and I invite them to 'splain it to me Lucy'.

The following bits of data is what I have picked up listening to others and thru some Google foo and put then together as to what made sense to me - I could be partially, significantly or completely wrong. Remember you read it on the internet. So, just for interest in trying to get a little more precise information, other things I calculate for each load includes:
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Mean Absolute Deviation (MAD) - Defined as the median of the absolute deviations from the data median. that is... starting with the residuals (deviations) from the data's median, the MAD is the median of their absolute values. The median absolute deviation is a measure of statistical dispersion.

the Excel Formula to use: AvgDev(x..y) [x & y are the range of chrono fps readings, each numerically listed in a cell.]

Why we care... MAD is more resilient to outliers in a data set than the standard deviation is. In the Standard Deviation, the distances from the mean are squared, so large deviations (hi/low outliers) are weighted more heavily in determining SD than fps numbers close together, thus outliers can heavily influence the SD. With MAD, the deviations of a small number of outliers are irrelevant and the resulting deviation number is more representative of the total shots fired.
============================
% Relative Standard Deviation- (RSD) - The % RSD value is based on the spread of results compared to the average. The result is expressed as a percentage - A low percent (<2.5%) means that the spread of results is small while a higher value indicates a large spread of results.

One issue with % RSD is that a sufficiently large data set is required; Although RSD requires a minimum of 4 data points, 10 to 20 will give satisfactory results. Typically RSD= SD/Avg*100 but to convert to % don't *100 (picked this gem up here on the form)
============================
95% +/- SD confidence level - Since the normal SD measures a confidence level of about 62.5% there is a good probability that you will have several shots with higher and lower velocities. You wouldn't know if there is something wrong with the load, a charge was off or what. By calculating the 95% confidence level you can be more certain of the expected fps range your load should be in, thus eliminating some false speculation.

I winged it when I came up with the following method, so those who do know, please enlighten me and I will refine my spreadsheet... I reasoned that if I took my mean velocity and added/subtracted the 95% level, that I would have a reasonable hi/low fps expectation range for any given load. Frequent fliers outside that range would be indicators to look closer at the load or discontinue it.

In the following Excel formula, Nn is the mean fps of chrono readings (aka avg fps), On:Xn is the chrono fps reading range and Yn is the SD of that range. Confidence is an Excel function calling for the 95% level and count is to only use the actual values in the data range and not skew the result with empty cells.
The formula to find the low velocity is +N20-(CONFIDENCE(0.05,Y20,+COUNT(O20:X20)))
The formula to find the high velocity is +N20+(CONFIDENCE(0.05,Y20,+COUNT(O20:X20)))

Here is an example of a recent 30-30 165gr LFP load with 9gr of 3N37...
Avg =1311
5 readings1309 1314 1299 1320 1312
SD=8
MAD=5
ES=21
low 95%=1304
High 95%=1318
%RSD=0.59%

We see that there are two values outside the 95% range. By extending the SD confidence range to 99% (change .05 to .01 in the formula) one of them comes into limit expectations but the other(1299fps) is still outside, so something was wrong with that particular load. it also may have been the flyer on the target.

As I shoot more of this load I will accumulate data and reevaluate the performance.

These methods will help you evaluate internal ballistics performance and help indicate stable loads vs erratic loads and if the results from one session/firearm to the next are consistent.

Accuracy of a load is a whole 'nuther aspect to the subject but when the two come together you have a weiner.

I had not heard or read about the "new" brass thing.

For consistency, the same head stamp or batch of brass all trimmed to the same length will probably make a difference.

It's all about repeatability and consistency.

Any scientific formula or test procedure relies on that.

Large variations in FPS could be caused by many things so if you have the same brass and length, that rules that out. Then it might be slight variance in powder charge. If you weigh each one then that is out. All bullets will vary a bit in weight so find 10 or more that are exactly the same.

Bench rest shooters probably spend hours mulling over this stuff.

Game shooters need the velocity of the bullet they are using to make power factor.

Of course check that mainspring screw to be sure the go BANG!

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Still Running Against the Wind

Thanks a lot, guys. Shooting just became a lot less fun.

Kidding!!! I recently purchased a chrono and this info is invaluable. The guys at the trap range were amazed at how their reloads and even factory loads varied.

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Fight socialism. Never stop.

Well I guess you can test the unit with 22 ammo............
I use a BB gun and it does just fine for me, a LOT cheaper too.

The longer the barrel the less ammo you need to find a good fps for a load. A 24 inch rifle reads a lot closer than a 2 inch snub nose with the way the powder burns and the pressures you get. I can see 10 test loads in pistols due to how the powder burns but the main reason for my 5-6 round test is to just get a "Ball Park" figure to see if it is close to factory ammo or what the recoil of the load might be in a given weapon. I some times toss out the low and high for a better average if things seem a little off and maybe shoot it again later on, if it looked promising, since most of the time I also shot at a target for accuracy test at the same time.

My chrony is touchy with lighting and some times does much better in the shade or on overcast days vs direct sun and the shields, even at ten feet where the muzzle blast of a pistol does not bother it.

I will retest a load that makes it to the "Finals" if it is a special load for hunting or SD work but usually with all my test with powders and bullets over the years, I get an idea of what the fps should be from all my notes. However a new bullet or powder gets a good work out.

I use NEW or once fired brass for my SD loads if not factory and no older than twice fired brass for my hunting loads. I will use 3-5 time brass for fps work if they are in good shape with no damage, 5+ is for my practice and target ammo.

Knowing a loads FPS is nice but I reloaded for 40 years with out a chrony and things still got done...........Accuracy is the name of the game but I do like my new "Toys".

I load for accuracy. The chrono is simply used to verify that my loads are within the desired velocity range.

And we have a winner!

Kinda makes it like work. Don't forget to bring the lap top and record all this data for future graphs, flow charts and spread sheets. I honestly hate (well dislike) setting up the darn thing, recording numbers, pondering them and yep. Then taking it down back in the car, Boy what fun.
Now this is out in the the heat and humidity. Not to bad if no one is around, then you gotta wait, cold range, set stuff up, other shooter giving dirty looks. Now that you brought it up, I hate reloading. I'd rather just buy and shoot like the old days.

OK I'm done now.

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Still Running Against the Wind

I should retract the new brass thing - I based it on what I thought I read - but after searching for it again - I can't find it

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I'd like to agree with you BUT

The Rifleman's Journal: Basics: Chronographing Effectively

http://www.precisionshooting.com.au/...phaccuracy.pdf

Chronographs and Pressure

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Still Running Against the Wind

Yeah I don't think I'd bring it out if there were other's at the benches - but I've been real lucky at my range with the no one around scenario. But if they showed up after I started - I got my stick

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I'd like to agree with you BUT

thanks fred, sorry - I read that wrong before

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I'd like to agree with you BUT

thanks Rule - I read the first one before I bought the Chrono - it'll help more now i have one and have used it a little
hadn't seen the other 2

gonna print them out for my night reading

some of you all have been doing this for awhile and it may not be as exciting as when you first started - but I'm eating this up

even now I'm writing up and charting today's completion of a chrono test that I started weeks ago

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I'd like to agree with you BUT

Wow 125JHP - thanks for all that - great stuff - I hope you wouldn't mind if I get back to you after I've been through all this info

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I'd like to agree with you BUT

thanks Nevada - how many lows or highs can I throw out??
just kidding

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I'd like to agree with you BUT

"Of course check that mainspring screw to be sure the go BANG! " ( post 12 )

Replaced a spring in my M19, M49 and a firing pin spring in my Win. mod. 70, due to weak primer hits.

The Old 1903, 30-06 is still going strong........ out lasted Three of my Timex !!

I don't understand how chronographing your test loads interferes with shooters using other benches on the same range. We do it all the time at our local club's rifle range and it makes no difference to the ones not chronographing. We all shoot and allow our barrels to cool at our own pace but pull targets together. The only effect having a chronograph sitting in front of my bench has on other shooters is prompting them to ask if they can run a round or two over it!

Ed

This is an older book that showed me just how serious one can get in
the pursuit of perfection. It also impressed the heck out of me and
I have read it more than once. I know no one who actually does all
this because I don't know any real accuracy champions.

Precision Handloading: John Withers: 9780883171325: Amazon.com: Books@@AMEPARAM@@http://ecx.images-amazon.com/images/I/618aMnFQ-pL.@@AMEPARAM@@618aMnFQ-pL

You don't have to buy from Amazon but I do recommend this book.
Get a used copy. I do that for a lot of the out of print stuff like
P.O. Ackley's gems.

As far as the interfering with others at the range issue, I do shoot
at a pistol range where it would be next to impossible to set up
a chrono (they even looked at me weird when I asked). I am getting
a Magnetospeed but it hasn't come yet. This should allow me to
get some data without leaving the bench. As it attaches to the
barrel, grouping and speeding will have to be done separately.
I mostly use the speed to make sure I am at a safe pressure and
cross reference it to as many load manuals as I can especially if
they use a similar gun.

Have fun! One can never have too much data in reloading. It's what
you do with it that counts.

---
Nemo

There are several inconveniences of trying to chrono at a public area... to Me not them.
First is the setup time - since it is in front of the line, you have to wait until a cease fire-range clear to do any setup, adjustments etc. AND set your targets.
Then there is the shorter time required for shooting test strings, so you will have to wait for another cease fire to change or check targets. Then if something unexpected happens, like wind blowing your target loose/over or the chrono or someone else shooting at your target, you wait some more and that string is hosed. It takes a lot of extra time working at an open range.

Working at my secret spot in the desert,I might test 10-20 different loads during a session. Without any interruptions, it keeps me busy 3-4hrs avg. I don't know how I'd get anything done on a public range. Depending on what I'm shooting, I use several targets for the strings which have to be changed out frequently or if I am using one big target for several loads, I like to go down and mark the holes after each string. I couldn't easily do that on a public range.

Is that my stick you are talking about? It's patented ya know.

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Still Running Against the Wind

I guess if you are chronographing at a public range as opposed to a members-only gun club, it might make a difference. I hang four to six targets at a time on one 4'x4' backer so I only have to make two trips down to them and none of us have any opposition to another shooter setting up a chrono or pulling targets during a lull in the shooting. Firearm ownership and shooting them is a hobby, not a job, so none of us are in a hurry and up to 12 of us can shoot at the same time.

Also, most of us "regulars" make it a point to arrive 30 minutes or so before our club's 9:00 a.m. shooting start time to do things like hang targets, set up a chronograph, drool over each others' guns and shoot some serious bull. It has to be a social event, you know...

Ed

no, no, no,
nothing like "YOUR STICK"

mine is an extendable "utility" pole and an eraser tipped "dowel" "rubber banded" to the end

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I'd like to agree with you BUT

It used to be that way several years ago, and I used to enjoy the 45min drive just to get there for some socializing. I was a RO for a couple of years but more idiots started showing up and that is a separate story. Now it is choked like a bus station, and the RO's have become like TSA, and you now also have to always watch your guns and your flank... it's no longer a fun day. The IDPA matches up there are a different story and i do enjoy them.

My peaceful & quite SSITD is about 15 minutes away, has a shady table to shoot off, has backstops at 50, 100 225 & 325yds.
You just have to keep an eye open for coon-tails.

I've read the above posts, and there are a couple of things to add.
1. STATISTICS: I teach statistics in college (yeah, one of those; my field is physics) and there is very little understanding of the staistical output from a chronograph for most users.
a. Why take 10 or more shots as the sample if you want to use SD? To have statistical confidence the average and SD of your sample actually is representative of your total ammo output, and not just a fluke. In other words, the SD from a small sample MIGHT be right, but you just can't be sure from a small sample. If you wanted to be 100% sure, you would have to shoot ALL your ammo over the chronograph (not practical). DON'T OBSESS ABOUT SD; it is more a gross error check.
b. How can I have a large SD and still have an accurate rifle load? Well pilgrim, if the vibrations of your barrel are such that the change in bullet speed does not change the position of your barrel when the bullet exits, then the change in speed does not change bullet impact. For handguns, I hear people fretting over speed variation that will produce only 1/4" difference impact at 50 yards when their skill is 6" groups at 25 yards. Of course you can't see the difference.
2. Chronograph setup: Most chronograph problems are due to setup errors, such as sunlight directly in the sensors, shooting too close, screen spacing incorrect, uneven lighting, looking into deep blue sky, etc.
3. Positioning the powder the same in the case for low loading density. For you light target load, try shooting a 10 shot string positioning the powder at the front of the case, and then shoot a 10 shot string positioning the powder at the back of the case. The average speeds will be different.
4. Calibrating chronographs. You can't. Sophisticated lab timing equipment is needed.
5. Why chronograph? If you compete, you have to make power factor or be disqualified. We get a lot of practice running chronographs at matches. If you reload, it is the way to know what YOU get in YOUR guns--and guns vary a lot!

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Science plus Art

Well I am suing based on patent infringement! But yours is clearly inferior, as mine has DUCT Tape (black), no rubber band to brake!

OKFCO5 was who I hoped would reply.

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Still Running Against the Wind

I agree with Rule 3 that too much is placed upon the chrono.
the 10 round min is reasonably valid.
hand weigh each charge .... sometimes yes, if your loading a batch of super duper uber match competition ammo where you'll hand weigh each charge for the whole run, while performing pagan rituals over each round to the deity of precision, under a full moon, with the usual accompaniment of 12 virgins, goat leggings and all else in accordance with the prophecy.

its better to test strings out of each batch exactly as run.
thats what you'll really be using.
that is, thrown charges, and loaded at production rate.
this lets you establish a real world set of standards where you can measure future runs against.
this practice lets you check to see that each run is up to those standards.
all the hand weighed, new brass, with all the voodoo trimmings does not reflect your run.

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it just needs more voltage

Just look at what a chrono has done to 125JHP

A monster has been unleashed!

MAD is Mutually Assured Destruction

Grow up in those days and you were more nervous than today.

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Still Running Against the Wind

I want to thank all of you for taking the time to share. Its great help to me and I hope many others too.
There a few people I still need to respond to regarding their posts. I have a set of data for 10 different loads I just finished testing that I will share very soon. I am applying quite a bit of what I just learned here to that data.

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I'd like to agree with you BUT