Chrono-madness!

[44Blam]

I just got a Chronograph and wow it's fun! Now I want to know - how fast is it???

I chrono'd some bullets I loaded for my .308 and tested out some loads. Got pretty good results, looks like I can drive a 178 grn bullet about 2500 fps before it starts showing pressure signs.
I also chrono'd some factory ammo - it was very consistent...

I chrono'd some 45-70 rounds I made and was AMAZED at how consistent it was with a min of 1803 fps and a max of 1831 fps -- with a 405 grain boolit out of my Marlin 1895...

I also chrono'd this little Russian CZ52 pistol - that thing was driving 80 grn 30 cal bullets at 1450-1500 fps!

That's some fun stuff right there. It also made me realize that I likely will not be able to push a lead boolit 2500 fps through my rifle, but my bet now is I should be able to get 2100-2300 should be pretty doable and will also work the action the way it is setup right now.

Next weekend's fun is 308 lead and chrono rounds from my Redhawk... I bet the Redhawk is chunking 240s at around 1400 fps...BUT We'll see!

[Hossfly]

Just be careful if its one that you shoot thru, and is 10’ In front of you. Don’t ask how I know.

[country gent]

Another thing to consider is to use a .22 rimfire with a good ammo or a spring piston air rifle and the same pellets to confirm set up and accuracy each use. Either will give consistant results over time. A tin of pellets or brick of 22s set aside for this lasts a long time proving the set up.

[Bzcraig]

Another thing to consider is to use a .22 rimfire with a good ammo or a spring piston air rifle and the same pellets to confirm set up and accuracy each use. Either will give consistant results over time. A tin of pellets or brick of 22s set aside for this lasts a long time proving the set up.

Good idea!

[MrWolf]

Replace the metal screen supports with wood dowels. Another trust me..

[country gent]

Weall it only takes a few minutes to fire the test rounds, and when done you know the set up is good and the chrono is reading correctly, with the test 22 or pellets. Just a way to save test rounds to know all is well before shooting them

[Jackpine]

And don't loan it to any relatives. (another "Trust me!")

[44MAG#1]

You didn't ask for advice so since this doesn't cost anything take it as you will. Here goes, ANYTHING you chrono only means one thing. It is a ballpark figure. It is not written in stone and never will be. Your velocities will be an ever changing thing to some degree or another. You can chrono a given load in a given gun today and test the same gun and load a period of time later and get another average velocity far more, far more , far more likely than not. Change one lot number of a component and that will change the outcome. change guns while keeping barrel length the same and that will change the outcome.
BALLPARK ONLY, no matter whether you use a five round string, ten round string, 20 round string or a 1000 round sting over the chrono. It is an ever changing thing.
That is the only fact you will have. Ever changing. Anyone that tells you it is isn't being truthful.

Again I mean no hurt, harm or anguish by my post. I am only making a statement based on my knowledge, experience and/or belief or opinion only. I am not trolling, baiting or calling out anyone by my post that I have posted on this posted subject.

[tazman]

You didn't ask for advice so since this doesn't cost anything take it as you will. Here goes, ANYTHING you chrono only means one thing. It is a ballpark figure. It is not written in stone and never will be. Your velocities will be an ever changing thing to some degree or another. You can chrono a given load in a given gun today and test the same gun and load a period of time later and get another average velocity far more, far more , far more likely than not. Change one lot number of a component and that will change the outcome. change guns while keeping barrel length the same and that will change the outcome.
BALLPARK ONLY, no matter whether you use a five round string, ten round string, 20 round string or a 1000 round sting over the chrono. It is an ever changing thing.
That is the only fact you will have. Ever changing. Anyone that tells you it is isn't being truthful.

This is correct. I have done the testing as 44MAG described and got the results he mentions. I also tried different firearms with the same length barrels and got differences on the same day with the same batch of reloads.
All you ever get is a ballpark idea of what to expect.

[Larry Gibson]

44Blam

However, keep in mind some loads can be played in a smaller "ballpark". It is those loads we seek, those that win the pennant over the "season"...... those that are the most consistent game to game or as we do with the chronograph; test to test.

If you are serious keep good records of the loads including the ambient temperature at the time of the test. Also set up the chronograph the same distance from the muzzle or bench each time. Average velocities will indeed vary test to test simply because the measured velocity of each shot varies. That's why there is an ES (Extreme Spread) and SD (Standard Deviation) calculation for each test string which give the average velocity. All three of those (ES, SD and average) are merely calculations of the measured velocities. The more consistent the load is the less the variation of those three calculations will be.

The fact you will have, if you are consistent in your testing, is that you have a 95% probability the average velocity (if a 10 shot test was used) of that load (same brass, same lot of primers, same lot of powder, same lot of bullets, etc.) shot out of the same test firearm under the same test conditions will be close to the same. As mentioned, change any one thing and...well....you have changed something so different results should be expected. Also mentioned, match loads shoot well in most any firearm made for them. Many "known" regular loads also shoot well in most every firearm made for them.

I have been using chronographs since the early '70s and have chronographed thousands of loads. It has been enjoyable and definitely a learning experience. Enjoy the trip ahead.

[dondiego]

And don't loan it to any relatives. (another "Trust me!")

Don't loan it to ANYONE, period! Trust me.

[44MAG#1]

44Blam

However, keep in mind some loads can be played in a smaller "ballpark". It is those loads we seek, those that win the pennant over the "season"...... those that are the most consistent game to game or as we do with the chronograph; test to test.

If you are serious keep good records of the loads including the ambient temperature at the time of the test. Also set up the chronograph the same distance from the muzzle or bench each time. Average velocities will indeed vary test to test simply because the measured velocity of each shot varies. That's why there is an ES (Extreme Spread) and SD (Standard Deviation) calculation for each test string which give the average velocity. All three of those (ES, SD and average) are merely calculations of the measured velocities. The more consistent the load is the less the variation of those three calculations will be.

The fact you will have, if you are consistent in your testing, is that you have a 95% probability the average velocity (if a 10 shot test was used) of that load (same brass, same lot of primers, same lot of powder, same lot of bullets, etc.) shot out of the same test firearm under the same test conditions will be close to the same. As mentioned, change any one thing and...well....you have changed something so different results should be expected. Also mentioned, match loads shoot well in most any firearm made for them. Many "known" regular loads also shoot well in most every firearm made for them.

I have been using chronographs since the early '70s and have chronographed thousands of loads. It has been enjoyable and definitely a learning experience. Enjoy the trip ahead.

While you are most certainly correct about the "smaller ballpark" what i am referring to is the braniacs that try to make it sound that what they find out in a chrono session is a "fact" which you and I know is never true.
Run out of your favorite powder, run out of your favorite primer and buy different lots of the aforementioned components and then see. One glaring proof of what I am saying look at the loading manual over the years. If it wasnt we would just need one the rest of our lives. We know they have changed. So nothing stays the same. Look at your photo in your high school yearbook and look in the mirror now. Wake up call.
I have been chronoing since one had to mount their own skyscreens on a piece of wood or some type of metal, "Tepeco Industries", im sure you will remember them.
That was certainly many many years ago when we both were much much much younger.
Just trying to keep both feet of the new chronographers on the ground. Where they should be.


Again I mean no hurt, harm or anguish by my post. I am only making a statement based on my knowledge, experience and/or belief or opinion only. I am not trolling, baiting or calling out anyone by my post that I have posted on this posted subject.

[Larry Gibson]

44MAG#1

Well the OP didn't come across as a "brainiac" to me. Actually I agreed with you ("As mentioned, change any one thing and...well....you have changed something so different results should be expected.")

Since we're talking about what irritates us let me mention what irritates me..... when someone posts something like; "I chrono'd 21 gr of 2400 under a Keith bullet out of my Ruger BH today and it gave 1230 fps....same load out of my S&W gave 1195 fps......" And they expect some sort of affirmation as to their "test" for whatever they think it means. No other information or details......irritating to me at least...... Know what I mean?

Let's not drift this thread, ok?

Or how about "average accuracy"... such as when 5 groups of 3 or 5 shots are measured then averaged for an "average accuracy" ....... how many really expect they shoot an "average"? Bet it's not just chronographers who don't have both feet on the ground over that one.......

[44MAG#1]

I used the wrong word and shouldn't have called anyone a brainiac.
I wasn't actually meaning any one particular person but I meant that as a generalized comment. Meaning me and anyone else that acts that way.
I made a mistake that people would understand what I meant. But I should have known that too.
All is my fault.


Again I mean no hurt, harm or anguish by my post. I am only making a statement based on my knowledge, experience and/or belief or opinion only. I am not trolling, baiting or calling out anyone by my post that I have posted on this posted subject

[44Blam]

LOL!
Why is it that every step I take to trying to shoot cast .308 in an AR cause an internet argument? :)

Anyway, it is an exciting step. I've chrono'd jacketed bullets from my .308 and have some data and I have a load for that bullet that I found to be accurate.

The next step is to see if I can get some cast boolits with a similar weight to run through the same rifle where it has enough power to cycle the gun and maintain accuracy and avoid leading. My expectation at this point is to be able to run boolits in the 2100-2200 fps range with accuracy, but I will work up to it.

The thing that REALLY made me happy is that I have a load for the 45-70 that is a load I have found to have accuracy in general shooting (eg, I can shoot clays at 100 yards consistently) ended up to have a spread of 28 fps over 5 rounds and is a 400 grn boolit trucking along at 1830 fps. Based on the load, I was estimating it at 1800 fps and it is "reasonable" to shoot. I cannot get the same kind of accuracy though because I cannot shoot it from a bench, it has too much recoil...

[Larry Gibson]

44Blam

No argument, just discussion. 44Mag#1 and I are further discussing it via PM......just different view points is all. Stay excited about your shooting and what the chronograph is telling you. You have received some helpful suggests most of which were learned the hard way..... like shooting the chronograph.....:roll: Hopefully you won't reinvent that wheel.......:drinks:

[Hossfly]

I’m just soooo happy we can have available a devise we can measure the speed of our projectiles, at the price of around $100. The numbers, not being perfect still mean something tho, just like thermometers you get different readings with different ones in the same pot of lead. I’m still amazed that chrono can time something moving at 3250 FPS, record,calculate,display,send to your phone etc. in that small of pkg. even tho I shot mine thru the top of back timer device it still works and very consistently. Still gives all data that it gave when new, lucky I quest.

[JoeJames]

I have learned a great deal from my chrono. For one thing it is a whole lot more important than I realized beforehand, that you should look very closely at what they were shooting when they got the published results, ie., what firearm, what barrel length, and of course what boolit? It really makes a world of difference. Example, in my Ruger BH 44 Special, I used the same weight of Unique = 6.8 grains, but with a Speer swaged .430" 240 grain swc it was @80 fps slower than with a .431" Oregon Trail 240 grain swc.

[rockrat]

Don't forget to buy another one. That way you can have one to use when you shoot and kill the first one (you will!!!, ask me how I know!!:))

[metricmonkeywrench]

Picked up a chrono for Christmas and recently got the Bluetooth add on for my chronograph and couldn't be happier, no more excel spreadsheets, and everything is recorded on the device society tells me I must have. Guess there is a reason to have a smart phone after all

With my cohort in crime/mentor I am learning to interpret the data, sometimes top speed is not the desired outcome if the load is not accurate or consistant.

Right now I'm working a .38 125g Power Pistol (4in S&W Mdl-10) load that seems to shoot ok as a plinking load, but when analyzing the data I have what appears to be a powder burn issue driving my extreme spread and standard deviation up. So something to look at in my reloading process and material selection to work on to drive these numbers down. Not to compare but to remove a variable the same pistol shooing a wad cutter load is almost boring for Chrono data low ES, SD and Av Velocity across the board which is to be expected with 3g of Bullseye indicating I don't have any barrel/cylinder issues.

[mdi]

Replace the metal screen supports with wood dowels. Another trust me..
Yep, BTDT! I was testing some 44 Magnum handloads and one of the metal screen holders just disappeared. I look for mebbe a half hour for that little guy, gone! Next day went to the hardware store and picked up some appropriate diameter dowels. Now if I hit one, it'll just break and I keep a spare or two handy...

[tazman]

Don't forget to buy another one. That way you can have one to use when you shoot and kill the first one (you will!!!, ask me how I know!!:))

I guess I'm just lucky. I haven't done that yet.I still have my original Chrony. I have a couple of others because the first one was difficult to make work but none of them have been shot.

[jimb16]

And remember that a scoped rifle has the bore well below the line of sight. (another believe me, I know)

[Forrest r]

Chronographs are the cat's meow for testing firearms for consistent ignition, bullet design & alloy.

Any firearm I want to use for competition or sd gets tested for consistent ignition. Get a firearm right & tight and the es's/sd's will drop which ='s consistency/accuracy. I've seen firearms cut their groups by as much as 40% when tested over a chronograph. Along with cutting huge swings in velocity out of short bbl'd firearms.

Bullet design plays a huge role in performance/velocity. A bullets performance doesn't matter as much in high pressure/high velocity cartridges. Start getting into short bbl'd firearms or looking for a hot hv hunting load that's accurate, a chronograph and a bunch of different bullets come in handy. Awhile back I did some testing with some short bbl'd 38spl's & 357's with these bullets along with a hbwc turned backwards and a hbswc.
https://i.imgur.com/0A0Ga7O.jpg
The 2 1/2" bbl'd 357 didn't care what bullet I used, was looking for a 1200fps 357 load and all of them delivered. So I chose a sd bullet based on the hp's performance. The 2" bbl'd 38spl on the other hand had as much as 50fps difference in velocities between bullets. In a 4" or longer bbl'd 38spl, it wouldn't matter. In 1 7/8" or 2" bbl'd 38spl's a difference of 50fps by simply using a different bullet is huge.

I've always liked a chronograph for testing alloys. Find an accurate load and then test softer/harder alloys looking for gains in velocity or the accuracy to drop off.

Anyway, yes a chronograph will give you numbers. What you do with those numbers is up to you.

[nun2kute]

SEE ! I knew I started coming here for a reason. Learn something new every day. Never before thought to test my tester. But I don't currently own a .22LR or a spring operated pellet gun. Now I got a good reason to tho. I recently got to the end of a box of test groups, (ten groups of five) the wide spreads didn't seem to corilate with the holey paper when the Chrono started actually adding shots to the groups, and blinking out. I got a spare battery, now I just need a spare test subject.

Just so you know, I have my original Chronograph with all its original parts intact. :coffeecom knox on wood

[murf205]

Replace the metal screen supports with wood dowels. Another trust me..

What he said. I learned the hard way! BTW, while you are at the range, there will always be someone who wants to shoot across your clock. NOT a good idea. If you want to give them a reading, do the shooting yourself AFTER YOU take a shot with their weapon at a target to make sure it will not splatter your chrono all over the place because their rig was not zeroed properly.

[metricmonkeywrench]

A rubber band shot across the sensors generally gives a indication of operating, plus they are easier to keep on hand and cheap to replace

[GregLaROCHE]

I just got a Chronograph and wow it's fun! Now I want to know - how fast is it???

I chrono'd some bullets I loaded for my .308 and tested out some loads. Got pretty good results, looks like I can drive a 178 grn bullet about 2500 fps before it starts showing pressure signs.
I also chrono'd some factory ammo - it was very consistent...

I chrono'd some 45-70 rounds I made and was AMAZED at how consistent it was with a min of 1803 fps and a max of 1831 fps -- with a 405 grain boolit out of my Marlin 1895...

I also chrono'd this little Russian CZ52 pistol - that thing was driving 80 grn 30 cal bullets at 1450-1500 fps!

That's some fun stuff right there. It also made me realize that I likely will not be able to push a lead boolit 2500 fps through my rifle, but my bet now is I should be able to get 2100-2300 should be pretty doable and will also work the action the way it is setup right now.

Next weekend's fun is 308 lead and chrono rounds from my Redhawk... I bet the Redhawk is chunking 240s at around 1400 fps...BUT We'll see!

So what make and model did you get? One’s on my wish list, but haven’t decided which one to get. It seems prices are really coming down compared to a couple of years ago.

[lightman]

I've found my chronograph results to be pretty repeatable. Not exact, but close. Temperature, humidity and elevation make a little difference. What I don't know it whether a displayed speed of say 3000fps is really 3000fps? As far as clocking the same load in different guns, I would expect some differences. After all, every gun does not the share the same pet load.

[Larry Gibson]

"What I don't know it whether a displayed speed of say 3000fps is really 3000fps?"

With screen spacing of 2 ft or less it probably isn't. It will be relatively close though but still there will be some error. The higher the velocity the greater the error.

Most modern chronographs with "sky-screens" are quite accurate as such. However, there are some things many don't know. The shorter the screen spacing between the start and stop screens the less likely the displayed velocity is correct to the exact fps. All chronographs use essentially (Magno-Speed and LabRadar excepted) the same crystal timers. The crystal "timers" pulse only so many times per millisecond thus at a given velocity there will only be so many "pulses" in the distance between start and stop screens. The more pulses per distance the closer to the actual velocity the readout will be. The number of pulses is converted to time which is converted to fps. Shorter screen distances have less "time" between screens and thus when the time is converted to FPS the readout in fps is usually a round up or down. The longer the screen spacing the more "ticks" between screens so the closer to the actual fps the readout will be. A 2 ft screen spacing is more accurate than 1 foot spacing. A 4 or 5 ft spacing is more accurate giving very close to the actual fps if not the actual fps. A 10 ft spacing is about as good as it can get from a practical stand point giving the actual fps.

Also the chronograph read out is the fps at the center point between the screens, not the muzzle. That is why for any valid comparison (accuracy wise) it is necessary for the screens to be the same distance from the tested firearm muzzles (within reason, does not have to be exact down to the thousandth of an inch).

[swheeler]

I just got a Chronograph and wow it's fun! Now I want to know - how fast is it???

I chrono'd some bullets I loaded for my .308 and tested out some loads. Got pretty good results, looks like I can drive a 178 grn bullet about 2500 fps before it starts showing pressure signs.
I also chrono'd some factory ammo - it was very consistent...

I chrono'd some 45-70 rounds I made and was AMAZED at how consistent it was with a min of 1803 fps and a max of 1831 fps -- with a 405 grain boolit out of my Marlin 1895...

I also chrono'd this little Russian CZ52 pistol - that thing was driving 80 grn 30 cal bullets at 1450-1500 fps!

That's some fun stuff right there. It also made me realize that I likely will not be able to push a lead boolit 2500 fps through my rifle, but my bet now is I should be able to get 2100-2300 should be pretty doable and will also work the action the way it is setup right now.

Next weekend's fun is 308 lead and chrono rounds from my Redhawk... I bet the Redhawk is chunking 240s at around 1400 fps...BUT We'll see!

Have fun with it! Next thing you know you will have data from tens of thousands of rounds with temp ranges from 100+ degs to below zero, shelves full of 3 ring binders! :bigsmyl2:

[murf205]

I have often wondered about the differences in the strength of the batteries as to the accuracy of the read outs. In other words, does the slightly weaker battery result in the crystal timer running slower that a new "hot" battery, or, is there a voltage parameter built into the circuitry.

[44Blam]

So what make and model did you get? One’s on my wish list, but haven’t decided which one to get. It seems prices are really coming down compared to a couple of years ago.

I got the Caldwell G2 - it was on sale for $155.

[Land Owner]

I hear some gas checks have been known to shed at the muzzle and then pass right through a sky screen. Something to think about in that...though I have not yet experienced it...and am considering a very light gauge forward shield to reduce that inevitability. Cannot be too heavy a shield or blow back/bound back might be the result.

[northmn]

I have had questions about my chronograph as to accuracy and such. What has given me the most questions is the discrepancy between what my chrono gives me and what some of the loading manual get with their tests. However, I have used 22 ammo as a test and have other results that tell me there are discrepancies. If a powder company publishes a manual it seems like they are on the high side. I am taking barrel length into account. Also, I have a Speer manual that published some of their chronographed factory loads and I get within their ball park.

44mag is not all wrong. He mentioned lot number changes. Target shooters that used factory ammo would buy several boxes according to lot number. Same for reloader and powder lot #'s. When I talk about manual differences, I use the same components they list. You also have exterior factors like ambient temps and altitude.

Another issue. I have had more than a little statistical training in my college days. For some reason chronograph manufacturers now using calculators include standard deviation in their read outs. Sd is a mathematical concept used to compute t tests or z tests, etc to see at what level your results could be due to chance. In other words, if you go through all this you can determine if the results are 99% accurate or 95% accurate meaning there could be a 1% or 5% chance that they were just random. For our purposes, average velocity, average variation and the total difference are important. Also, a 5 shot sample is not all that accurate. Saying this I still often use a small sample and take my chances. You have to have something left over to shoot.

My chronograph has been fun and I consider it an important tool. I just used it to test the difference in results I might get with using Starline cases vs Winchester and for that load out of that rifle found them to be insignificant. Also I have loaded up some loads and wondered if they were giving me what I thought they should and have been either reassured or had my suspicions verified. I used it to test the differences between firing a muzzle loader with a clean barrel as opposed to a fouled barrel as we used to foul barrels in matches. It explained why. Even used my chrony to test shotgun loads.


As to other recommendations. Don't lend them out and don't borrow one. I bought one to replace one I borrowed. Take their advice seriously.


DP

[murf205]

I hear some gas checks have been known to shed at the muzzle and then pass right through a sky screen. Something to think about in that...though I have not yet experienced it...and am considering a very light gauge forward shield to reduce that inevitability. Cannot be too heavy a shield or blow back/bound back might be the result.
I have never had GC smack the front of my chrono but I have had a shotgun sabot shed the slug and hit the face on my 1st Chrony. Amazingly it still worked but it had a pretty bad dent in the face. Since then, if I am going to clock a saboted round, I use a piece of 1/8" steel plate that I fabricated in front of the chrono.

[44Blam]

One thing that was interesting was my friend was shooting his .223 near me and when he was firing, it would register but at relatively low velocity.
He was shooting 55 grn factory rounds which should be going in the 3000fps range and it would register in the 1500 fps range.
I am assuming it was somehow picking up the shock wave from the super sonic bullet or maybe the gasses trailing the bullet? Anyone know why this would happen?

[country gent]

What chronograph were you using? Sky screens the bullet has a some what narrow window to pass over to register. It may have been light angle throwing shadow on the sensors. Gasses tripping it would read faster. On the lab radar ive not had issues with shooters beside me being picked up, I do occasionally get a off reading from a wad being picked up in my BP loads. On my pact professional the smoke plume would give off readings or errors. Ive never worked with the Magneto speed but again a very narrow area for the bullet to be picked up.

[JBinMN]

One thing that was interesting was my friend was shooting his .223 near me and when he was firing, it would register but at relatively low velocity.
He was shooting 55 grn factory rounds which should be going in the 3000fps range and it would register in the 1500 fps range.
I am assuming it was somehow picking up the shock wave from the super sonic bullet or maybe the gasses trailing the bullet? Anyone know why this would happen?

I don't know, but it would be a Great question to ask Caldwell.
;)

I have a Caldwell, although not the same type as yours , but have not had that issue with it... yet...
;)

[Hossfly]

I’ve shot beside mine with it on and it doesn’t read anything.Caldwell or Chrono. I’ve shot thru both in series for test of readings and both are consistently on the money.

[Three44s]

One thing that was interesting was my friend was shooting his .223 near me and when he was firing, it would register but at relatively low velocity.
He was shooting 55 grn factory rounds which should be going in the 3000fps range and it would register in the 1500 fps range.
I am assuming it was somehow picking up the shock wave from the super sonic bullet or maybe the gasses trailing the bullet? Anyone know why this would happen?

I have a Chrony and have had trouble on days of part sun/part clouds with erratic readings. That would be my first pick as to the culprit. But I have not used Chronos a lot.

But it was always enlightening whenever I did include them in a session.

Best regards

Three44s

[scotner]

And remember that a scoped rifle has the bore well below the line of sight. (another believe me, I know)

Oh really? Thanks for that tip.

[northmn]

My chronograph works best on sunny days. If I remember I have seen some with light stands to accommodate that situation for cloudy days? I think that might explain the error in readings on the 223. Most of the differences I have seen between actual readings and data are within reason. As I mentioned, most of my readings are less than the loading data shows and I have heard others claim that. However, I remember one with the 38-55 where the data was way off. I was getting about 1650 with a load they claimed should have been at best about 1400 or so. I was shooting a cast bullet and the load did not shoot that well. When I used less powder and got lower readings it shot better. Other loads from that source with other powders were closer to the data. The data was based on a 30" barrel?


I had formal training in Quality Control and worked in that area just before retirement. In manufacturing, products are made that have "acceptable variation" In another words nothing is perfect. Todays technology permits more precise products, but there is still a variation. Generally speaking the less acceptable variation engineered in a product the more expensive it is. I have no idea what the variation is for the more inexpensive chronographs on the market. Some might be right on and a few might be a bit off, but within specs. The variation tends to follow a bell curve and most sent out will be within one SD of the target. Consistency in a chronograph is very important and most are probably consistent, such that one can teat a few shots and see whether the load tends to give the same velocities or is all over the place. Most of us like to do shot to shot comparisons.


DP

[Petander]

Congrats for the chrono,they can be addictive.

I chrono everything,all the time since -95. Pay attention to the angles you shoot through the screens. To repeat and compare you want everything straight.

I have a level table with marks for the chrono,always use the same target rock in the 75 m berm and I shoot from the same exact footsteps/position every time. Chrono & Quick Load have taken quite a bit of guesswork out of my reloading.

229367

[crackers]

Aim high.

[jimb16]

Erratic reading from chronos are often caused by weak batteries. Try changing them for fresh ones and see if the problem goes away.

[Larry Gibson]

Since my last post regards the accuracy of chronographs based on screen spacing I did a bit of research to get the exact amount of possible inaccuracy based on the screen spacing. We see here the smaller the screen spacing gets the larger the error. Short screen spacing of 1' along with minimal test sample are responsible for the multitude of very small SDs reported these days.

CRYSTAL OSCILLATOR FREQUENCY:
4.0 MHz oscillator for 0.25 microsecond time resolution.

ACCURACY:
The expected error on any one shot depends on both velocity and screen
spacing. Typical errors are shown in the table. The table assumes good light
conditions, dark bullets, exact screen spacing, and shooting through the
center of window.

Screen spacing 1 FT 2 FT 4 FT 8 FT

1000 FPS 5 fps 3 fps 1 fps 1 fps

2000 FPS 10 fps 5 fps 3 fps 2 fps

3000 FPS 16 fps 8 fps 4 fps 2 fps

4000 FPS 21 fps 10 fps 5 fps 3 fps

[44MAG#1]

Of course all of you know I sure dont know anything, but the more that chronographing is investigated the more varibles we have hence the more incaccuracies we have so maybe we should leave the chrono in the box on the shelf.
When one considers the amount of errors that can be had, especially starting with the operator (like me), to the inaccuracies of the machine itself, the shelf seems more attractive. That would save some more time for honing ones skills etc.

Again I mean no harm, hurt or anguish by my post. I made the post I made on this posted subject based on my knowledge, experience and/or belief or opinion only. I am not calling out, trolling, baiting or belittleing anyone here. Please take no offense to my post.

[Larry Gibson]

Have to politely disagree. Todays chronographs, even the ones with 1' spacing, are excellent tools. They can provide us with important information regarding the ammunition used in our firearms. Like any other tool, if used incorrectly or if the resulting data isn't interpreted correctly, perhaps they should be left on the shelf. It does not take "rocket science" to use a chronograph correctly. It is a matter of consistency of use, using sufficient input (# of test shots in a string and test conditions [ambient temperature and pressure]) and simply understanding the data measured.

Those 3 items are the reason many reported; not placing the start screen the same distance from the muzzle (within reason, does not have to be to the exact inch) test to test. Not noting the weather conditions as the temperature will affect the velocity. Not using enough shots in a test string and not using enough test strings of the same load to get a sufficient average velocity +/- for a given load.......one 3 or 5 shot test can give us an idea whether the load is worth pursuing but it tells us nothing about the true "average velocity" of that load out of that firearm. Lastly, we must interpret the most often used data most chronograph readings give us; the Extreme Spread and Standard Deviation.

The SD is the most often used indicator of uniformity of a load. The more accurate the chronograph measures the velocity of each shot the more accurate the SD will be given a sufficient # of test shots. Quite frankly, given the built in potential error, I do not give much credence to any reported SD with screen a spacing of 1'.....most of the Chroney's" and a few others, especially if only one test string is used of less than 10 shots. If three 10 shot strings are tested with a 1' screen spacing then a better indicator may be the ES of the lowest velocity to the highest velocity recorded in all 3 test strings. The SD of a 10 shot test string tells us that probably 2/3 of the shots fell within a +/- the SD of the average velocity.

So how are we to know? First let us remember we do not shoot "average velocity", each shot will probably be a different velocity. The trick is to get all the velocities close together. That's not to say using the "average velocity" as computed is not useful. With a good load we should chronograph at least 3 ten shot test strings under the same conditions. That will give us 3 "average velocities". We can then average those velocities and come up with a much better "average velocity" based on the 30 shot test sample. Then taking the lowest velocity and the highest velocity of any shot fired gives us the +/- velocity (ES) for that load. The benefit of that method is the average velocity obtained can be entered into several ballistic programs along with correct other pertinent data and the resulting down range ballistics will be very close. The SD can also be averaged but as noted with a 1' screen spacing it really isn't the best indicator of load uniformity.

The chronograph is indeed a useful tool, we just have to use it correctly.

[44MAG#1]

Larry Gibson,

I completely agree with you on your summary of the whys and the reasons one should do a test as completely as one possible can.
But how many actually want to do that? I wouldnt mind with pee ant cartridges etc. But me testing maybe 4 different loads in maybe three guns in 44 Mag by shooting three ten shot tests of each load back to back in the same morning is not going to happen. I dont spend a half day at the range much less a whole day. Now ramp that up to a 454 Casull on up and the likelyhood is even less. Just like the senario i posted in the last PM i sent you about my 14 inch Encore in 458 Win Mag.
I dare say if most are honest about it most are not going to do some long drawn out test. They will shoot five to ten shot strings and that is about it. Especially if they have several loads to test in a hard kicking gun it more than likely will be five or six. Powderpuff recoil may be different. And if someone wants to spend time to do it with powderpuff recoil guns that would be good.
I am all for as much accuracy in results as can be obtained whether it be shooting at a target or chronographing or the loading of the ammo. But with me reality rears its large head in every direction.
Ive see several people chronograph rifles and handguns, but mostly rifles and have never, never ever seen anyone put much attention to it except chronographing generally five rounds of each load, but sometimes ten rounds of each and that was far and few inbetween.
Again I am on the same page with you but I see a different reality in the same picture.

I guess I am really saying, trying to be somewhat of a diplomat about it is, no matter how little data one gives or how much there will always be someone to pick apart what one does.
One could give 99 pieces of information on what they did or how they did it and someone would be saying where is the 100th piece of information.
Just like most bosses one works for, no matter how much one works their behind off there is always some supervisor that says well you didnt do this and you didnt do that. What did you do sit around all shift? It is especially bad on night shifts. That probably where I have gotten my mindset on things.
Then supervision wonders why employees have the attitude they have.
I guess my mind has been colored by my perception.
Someone said one time: "Ones perception becomes their reality." That hits the nail on the head as far as Im concerned.

Sorry for my insight on my nearsightedness carry on. No more from me on this subject.

Again I mean no hurt, harm, anguish or turmoil by my post I have posted on this posted subject. I am not baiting, trolling or calling out anyone. I am making a post based on my experience, knowledge and/or belief or opinion. That is all.

[northmn]

I was a graduate assistant that helped to set up research for the phd's. Most of the issues in research is finding an appropriate subject size to be significant. Generally 10 was minimal and 15 was considered better. Also, another important issue is the control of variables.
For chronographing things like temperature and distance from the screen as well as adequate sun light would be variables.


Step back a minute and look at some of the things Larry G has presented. Error for a 1' screen is about +or-.5%. Is that all that important?
The distribution of shot to shot variances exceeds that, usually to a large degree. The error itself may be somewhat of a constant. I am darned if I want to set up an 8 ft screen spacing just to get minor difference in so called "true velocity". The use of average variation or extreme spread is about as good as we need. ES is probably as useful as any. A sample like 5 shots is taken to give an idea of what you might get out of a total population. For instance with factory run of a lot number of ammunition is a population. A 5 shot sample may or may not be close to the actual results if we tested all the ammunition manufactured in that lot. Unfortunately what we are doing is called destructive testing. Once shot the sample is no longer available for use. So if we shot up the whole lot it would not be a practical project. Larger samples are then used to get a more comfortable indication of the population. Note I said more comfortable. A 5 shot sample might be adequate. If put to a statistical test it may give a 90% probability that it represents the whole lot size (been a while and I don't remember the numbers, it probably is less). A 15 shot sample maybe better than 95%. This goes for any tests, from accuracy to Chronographing. Handloaded rounds could be based on a can of powder, a box of primers or a box of bullets.

What we choose as a minimum sample is based on how much effort is desired and how important to us the results are. A target shooter looking for the absolute best accuracy may want to shoot more samples than a hunter looking for an indication of how effective the load may be. I have never seen any one publish a t test for their results in testing ammo, just results. For instance a 5 shot group of 1" may or may not be representative of what you could get from the whole lot size. It is only significant at a lower level and 9 more groups might give a much different spread or might be within that parameter. One of the groups may not be. The whole game is based on probability and our desire to test for an adequate chance of being correct. This has been somewhat of an egg headed explanation, because basically the 5 shot tests have made most folks happy.


DP

[Larry Gibson]

44Mag#1

As to the reality of chronograph use obviously, as the old adage says; you see the glass as half empty, I see the glass as half full.

"I completely agree with you on your summary of the whys and the reasons one should do a test as completely as one possible can.
But how many actually want to do that?"

Many of us do, but most don't. Why? The reason is simple; they read posted average velocities on forums like these with no details as to how the test was conducted. They read of 3 and 5 shot tests in gun rags and think that is the best way. The instructions received with their chronograph are generally rudimentary on the operation of the chronograph with no explanation or maybe just a hint of what a valid test might be. There aren't any books on how to properly chronograph/test ammunition. Where on this site or any other is a proper methodology of chronographing/testing ammunition to be found for most to read......how many really read and study the available information anyway?

Dr. Oehler's White pages are published on the Oehler website which gives good information. SAAMI's website also has good information. Some of us have posted lots of test results and methodology on this forum. My tests have also included numerous test loads in "hard kicking guns" including numerous "back to back" tests. I have to ask; If one can't handle the recoil maybe one should question the validity of shooting them? There are also numerous methods to mitigate recoil when bench shooting for a proper test. Perhaps a little research as to how on your part may ease the recoil situation?

Short answer is many use 3 and 5 shot test strings (sometimes even just 1 shot) simply because they don't know any better or, as you state, because that's all they want to do. That's fine with me....they do what they want and I do what I want....fair enough?

[Larry Gibson]

northmn

"A 5 shot sample might be adequate."

To the gun rag writer, the casual shooter or to those who don't know better it may be. However, industry standards (including ballisticians) do not believe it is "adequate" to predict any level of "surety". A 10 shot test with multiple tests to confirm specific loads is the considered adequate. A read of the SAAMI Manual would provide the why's.

If may quote Dr. Oehler;

"Chronograph systems with inadequate spacings between skyscreens often
give passable readings of average velocity, but questionable readings of
standard deviation. Whenever you use standard deviation, remember there is
an important corollary of Murphy's law. Its regular use can replace many
mathematical theorems and complicated statistical procedures.

Large groups usually repeat;
Large groups with large standard deviations always repeat;
Small groups caused by luck never repeat."

[44MAG#1]

I made the statement that I would post no more on this subject but let me say this. Recoil? At one time I could handle just about anything out there and shoot groups that would be far better than most with lighter recoiling handguns. Not bragging just telling the truth. I could keep going up until others aould finally drop out. Stupidity on my part cetainly. I could do it it. Could I do it now at 66 years old? I dont know. The 44 Mag is about all I shoot now but that is not heavy recoil. A couple months ago I shot my BFR 45/70 with the 7.5 inch barrel using 515 gr bullets at a (now remember I chronoed this load which is very suspect) at slightly over 1400 fps and did very very well offhand. Its been close to 2 years since I shot my 458 Win Mag Encore. But still did well offhand. Not as well as I did years ago. But I will go a round or two with anyone that wants to have a contest with the two aforementioned guns. Out to 100 yards offhand.
Many years ago I had a 460 Weatherby and it wasnt one that a person would want to sit at the bench and crank out round after round after round with that gun. Not in one morning of testing. I would take a couple Bufferin (remember those) before leaving to go to the range.
While not engaging heavy recoil much at all now I could still be stupid enough to do it..
Maybe Ill load up a few 45/70's for next week.

Now I am absolutely through with this thread. Because my perception hasnt changed when it comes to chronographing
Maybe some day Ill change but i doubt it since I dont have as long to go as I have gone. Time is moving faster and getting involved in the idiosyncrasies of chronoing is not in my daily log.
Maybe some younger person can get fully involved in it. I will be happy for them.

Again I mean no hurt, harm, anguish or turmoil by my post I have posted on this posted subject. I am not baiting, trolling or calling out anyone. I am making a post based on my experience, knowledge and/or belief or opinion. That is all.

[jonp]

Just be careful if its one that you shoot thru, and is 10’ In front of you. Don’t ask how I know.

Hmmm...I posted a thread a while ago on the order of "I got a new chrono, I just shot my new chrono". :p

Just used my Caldwell today to check some Unique loads in my 32 H&R Mag Rugers. Velocity is far lower than it should be for 100gr RNFP. The great thing about the Caldwell kit I bought on sale during Black Friday last year is that is has a direct cable hook-up to my Galaxy phone and I can save then download the data. Very nice.

[jonp]

northmn

"A 5 shot sample might be adequate."

To the gun rag writer, the casual shooter or to those who don't know better it may be. However, industry standards (including ballisticians) do not believe it is "adequate" to predict any level of "surety". A 10 shot test with multiple tests to confirm specific loads is the considered adequate. A read of the SAAMI Manual would provide the why's.

If may quote Dr. Oehler;

"Chronograph systems with inadequate spacings between skyscreens often
give passable readings of average velocity, but questionable readings of
standard deviation. Whenever you use standard deviation, remember there is
an important corollary of Murphy's law. Its regular use can replace many
mathematical theorems and complicated statistical procedures.

Large groups usually repeat;
Large groups with large standard deviations always repeat;
Small groups caused by luck never repeat."

^^^+1

I'm interested in velocity for what I do as it relates to either what is needed for proper expansion in the jacketed i'm using or cast performance. Keep in mind that velocity is one piece of the puzzle.

[northmn]

northmn

"A 5 shot sample might be adequate."

To the gun rag writer, the casual shooter or to those who don't know better it may be. However, industry standards (including ballisticians) do not believe it is "adequate" to predict any level of "surety". A 10 shot test with multiple tests to confirm specific loads is the considered adequate. A read of the SAAMI Manual would provide the why's.

If may quote Dr. Oehler;

"Chronograph systems with inadequate spacings between skyscreens often
give passable readings of average velocity, but questionable readings of
standard deviation. Whenever you use standard deviation, remember there is
an important corollary of Murphy's law. Its regular use can replace many
mathematical theorems and complicated statistical procedures.

Large groups usually repeat;
Large groups with large standard deviations always repeat;
Small groups caused by luck never repeat."

You misunderstand what I wrote or missed my point, or I did not make things clear enough. Tests are based on probability. There are standards that you have mentioned that are standard sampling procedures. Because you are dealing with probability a 5 test might be a fair representation of the population or it might be in left field. I have yet to read a test in a gun rag using proper significance testing to explain at what level of probability their results reflect the population. When people shoot a group it is a 5 shot group and then publish it. When they pattern a shotgun they do 5 patterns. SD does is used to determine the variance from the mean. On smaller samples for purposes of shooting the average person is best served using Extreme spread and forgetting about variations as they are based on finding the mean which on small samples may be quite a bit different from the actual population mean or "real mean" .

Every thing you have presented is standard to what I have been trained in. And is what I thought I said earlier. The point I was making is that if one buys a pound of powder to reload and wants to test loads out of that can he may want to have some left over to use instead of running so many tests that it is used up. I would have to go back and recheck but the probability a 5 shot test may reflect the real population is somewhere above 80% Which leaves a 1-5 chance it is not. Sometimes people get fooled by the 5 shot results that are the result of pure chance. Often they go back for a retest.


Just because someone has a Dr. in front of his name does not mean he what he writes makes sense and that is his "questionable readings on standard deviation" I would like to see more elaboration on that as I have stated SD is a tool for more advanced tests and by itself may not mean anymore than average deviation. Many statisticians call the SD a statistical fudge factor.

All of this has to be applied to practical applications of use. If a hunter tests a rifle and gets a 1 inch group chances are that he is going to hit a big game animal where he wants to at under 200 yards. A varmint shooter might want a more thorough test or more likely to come back and recheck his results.

As I also mentioned, you have to control variables. I used a powder and loaded for a 300 Savage bolt action I had. The manual stated it should be 2700 fps. Something about its general performance made me curious so I chronographed it. It was lucky to give me 2600 using the same components and the same barrel length as the data. However I tested it after deer season and the outside temp was below 40 degrees. I made sure the cartridges were at that temp. Its very likely that the data was taken in much warmer weather. Saying that it was an accurate load and it took a deer. So what did the test really prove?

DEP

[Larry Gibson]

northmn

I didn't make my self clear apparently, I was not disagreeing with you. I was elaborating on what you said. Your explanation of testing based on probability is spot on.

"Because you are dealing with probability a 5 test might be a fair representation of the population or it might be in left field. I have yet to read a test in a gun rag using proper significance testing to explain at what level of probability their results reflect the population. When people shoot a group it is a 5 shot group and then publish it."

"or it might be in left field." Exactly.....the point is with just a single 5 shot test you just don't know whether it is a fair representation, maybe kind of close or "in left field". Unfortunately many here and on other forums just post the average and we have no idea of which it may be. Having pulled the test sample information out of a few I find the resulting "average" is still in the ambiguous category.

"Just because someone has a Dr. in front of his name does not mean he what he writes makes sense and that is his "questionable readings on standard deviation" I would like to see more elaboration on that as I have stated SD is a tool for more advanced tests and by itself may not mean anymore than average deviation. Many statisticians call the SD a statistical fudge factor."

I certainly agree that a "Dr." in front of a name does not mean a person knows what he's talking about. However, in the case of Dr. Oehler we can expect he knows what he is talking about given his reputation and expertise in the field of chronographs, their development and in the field of the measurement of internal and external ballistics. He developed chronographs, including the use of radar, for long range ballistic measurement of not only bullets but cannon and artillery projectiles. If you read his white papers you would find an elaboration of SD. And yes, SD is a fudge factor. Over the years having tested thousands of tests of velocity, TOF and psi I have seen enough SD "fudges" to not trust a low SD alone as a real indicator of a "uniform load". I've come to believe there s a direct correlation between the SD and ES in the most uniform loads.

Most published tests these days are the result of multiple 3 or 5 shot "groups"....usually 5 such "groups". That gives a reasonable sample of 15 or 25 shots for the "averages". But, again, we don't shoot "averages"....each round fired will have it's own velocity which most likely will not be the "average" velocity. In our "probability" measurement of the average velocity (assuming we had a sufficient test sample) the SD means that about 2/3s of the shots we fire with that load will fall +/- the SD velocity of the average velocity. That also means that 1/3 of the shots fired will be outside that SD range and with a probable 90 to 95% surety their velocity will be still within the ES velocity range. So how do we know which round is in the 2/3s SD range (the assumed most uniform and thus accurate) or the 1/3 range of the remainder velocities.......we don't. Thus we want a load with a small ES and an SD that is about 25 to 40% of the ES.......along with excellent grouping for the firearm type. That is what the results of my own extensive testing over the years is demonstrating.

"Saying that it was an accurate load and it took a deer" answered the question as to "what did it prove". In my estimation not knowing the parameters of the test, the reason for the test and not seeing the results of the tests it is difficult to offer a specific answer. However, sometimes it's just difficult to doubt success and perhaps that is the best answer......:drinks:

[northmn]

It is said that communication is at least 60% non verbal which I see leads to misunderstandings on these sites. I enjoy a good conversation and I see that we are using different backgrounds to discuss the same issue.

I have done shotgun pattern work probably as much or more than rifle work. Due to the work involved that gets tested with a lot less formality than rifle testing. There was an individual on a shotgun site that would post his 5 shot pattern averages and the discussions on what made a "better" load were amusing. Most of the time the patterns showed that the major ammunition manufacturers were making about the same product and one could just about grab blind off the shelfs. But using percentages can be somewhat misleading and the highest percentage got the best accolade. As I preferred to let him do the work and could do some review of it I preferred not to be too critical in comments.

There is a direct correlation between SD and ES. SD is an application to the normal curve that statisticians believe exists for most populations and covers the 67% or 2/3 you are talking about. If the range of the normal curve (ES) is smaller then so is the SD.

I had to help set up experiments as a grad assistant and also evaluate many of the writings in the obscure publications that phd's had to get published in to keep their jobs. Many of their "research articles" were of poor design and while may not have been false were not proven to a comfortable level of significance. Another issue about doing these experiments which chronographing, shooting groups or patterns are, is variable control. When an experiment gets published it has to include a description of possible variables or outside influences. As an example if one was to properly describe a series of velocity tests one might say that the temp was x, the humidity x, sunny day/cloudy day, altitude at x etc. The results are for those conditions and anything taken other would be a "generalization" Generalizations are considered a kind of common sense interpretation of the results.


Gets kind of complex and setting up true experiments a lot of work. As I do this for fun I don't do a lot of it. By the way the individual that did the patterning. I tested some loads also with a different gun, same choke at a measured 40 yards and duplicated his results. So most of the time what he presented was a good indicator. One test of a study is replication.


DEP

[Larry Gibson]

"There is a direct correlation between SD and ES. SD is an application to the normal curve that statisticians believe exists for most populations and covers the 67% or 2/3 you are talking about. If the range of the normal curve (ES) is smaller then so is the SD."

That is the correct generalization regarding SDs.......but the devil is in the details, especially when testing loads and interpreting the correlation between the ES and SD. Here is what I have seen all to often. Lets say we have 2 loads for the .308W for 1000 yard match shooting which we've shot a 10 shot test string with. Both loads shoot consistent moa 10 shot groups at 100 yards.

We get the following data from the first test;

Hi; 2580
Lo; 2520
Av; 2550
ES; 60
SD; 10

That is telling us 7 of those shots were in the 2540 to 2560 fps range for a 40 fps spread while 3 of those shots were below and above that range by as much as 20 fps for the ES of 60 fps. May not sound or look like much of a difference but at 1000 yards, if you're X ring capable, those 3 shots can easily put your bullets into the 10 ring or into the 9 ring. If just ten ring capable then you're looking at dropping upwards of 3 points or more just because of the "probability" of that load......that's if all else goes well during the 10 shots.

Then let's say we have the 2nd load with another powder that gives the following data;

Hi; 2575
Lo; 2525
Av; 2550
ES; 50
SD; 20

However, with the 2nd load 7 shots would be in a 40 fps range (same as the range of the 1st loads 7 shots) with the remaining 3 shots only a possible 10 fps higher or lower. The 3 shots of the 2nd load are thus closer in velocity to the 7 velocities within the SD. As we can now see the 2nd load is actually a more uniform load if we consider all 10 shots regardless that the 1st loads SD is half the size.

Those that chase the SD god would tell us the 1st load is the better and more uniform load because the SD is 10 and the 2nd loads SD is 20 regardless that the 2nd load has the smaller ES. Yet in actual practice the 2nd load will hold X ring or just into the 10 ring at 1000 yards. I know because I "been there, done that" with both loads. So yes there is a "direct correlation between SD and ES" but, in reality on target, there is more to it than "the normal curve (ES) is smaller then so is the SD"

As to "variables" during a test I refer to them as "conditions" because that's how I was trained to call them in my sniper/high power match shooting days. If you've looked at any of the Oehler M43 PBL data sheets I've posted you will note the "conditions" such as temperature, atmospheric pressure, humidity, altitude are all entered along with a plethora of other "conditions" such as screen set up distances, wind velocity and direction, etc. Also, as I've mentioned, I've tried to get posters to at least give some information on those "conditions".....many times it's like pulling teeth though...... Also, I have many times suggested to users of chronographs to at least set the start screen up the same distance from the muzzle, note the ambient temperature, to shoot a sufficient sample of shots and to retest at least 2 more times any promising load. It's really not that difficult to do.

Some, if not most, use the chronograph to simply tell them the average velocity of their loads. That is fine and still useful to them because the answer applies directly to their gun and load. However, if comparing the test results of various loads against one another or is reporting them for comparison to what others have done then the "conditions" (variables) must be known for any accuracy in the comparison to be valid. Again, even then, certain of those "conditions" must be consistent for any valid comparison other than a generalization.

[northmn]

In the book "How to Lie With Statistics" (sorry can't remember who wrote it) the use of variance measurements was explained when he stated that the average yearly temperature in Montana or Colorado? is the same as that of Hawaii. True but the variance is what is most important. The SD for Montana is probably larger than the ES of temps in Hawaii. To be precise the 67% for a SD is actually 2 SD's one on the plus side and one on the negative side. We presume that a variation of 25 fps has the same effect if less or more so we talk of 1 SD of variance.

The proper term for SD is "the standard deviation from the mean" Some forget what that truly entails. When you chronograph smaller samples you get a SD readout on some models and a mean. That SD is unique to that mean, but is that mean the "true Mean". Same for the Average deviation from the mean. What you have in say the pound of powder I mention is a Mean velocity given you use it up on the same load. Your samples will give an average or mean that distribute similar to a normal curve around the Mean of the whole can. The deviations are however from that Mean the sample statistics are hopefully close enough for an adequate representation. But some of the SD variations one encounters is due to the fact what you are seeing is the regular deviations from a different mean than the Mean

Jonp made a point about using the chrono to test for bullet performance itself. I often do that also. I look at tables etc and desire a velocity that will work well with a given bullet just as he mentions. That does not take a lot of effort.

You are properly setting up experiments the way they should be done. I can imagine the frustration, Note I mentioned that an experiment is considered good for the conditions or variables in which they are completed. I could easily decide that I want to take a control load and see what effect temperature may have on that load. Is it consistent at 70 degrees but does it get squirrely (I like that as a technical term) at 90degrees. Then if does is it the powder or the primers? So another experiment. The amount of experimentation gets pretty overwhelming.

As to terminology temp and barometric pressure would be conditions, and distance from the screens are controls. All are variables. Looking at your procedure you can call them what you want as you are doing about as well as you can and better than most. Component change such as production lots could also enter in. I just read where a new 1000 yard record was set. Everything came together that day including maybe a little luck? By luck I don't mean to belittle the achievement on skill but on the fact that the sample he shot to score may have been one of those that did not have the same variation he might have had with Murphy's sample.


DEP

[northmn]

I did not quite expect to get into this type of discussion. I would get amused when someone lists say the results for a 10 shot or 5 shot series over a chronograph and kind of smugly comments on its small SD. Very few understand what a SD is and what it is for. Mostly I set back and read the results and appreciate the work and take note of them. If impressed enough I will see if I can duplicate the results. Those of us who play with a chronograph do so for different reasons and have different goals. Someone shooting at 1000 yards and developing loads is going to have to be more rigorous than an old deer hunter like I am. If I shoot a nice group, even if it is a bit of a fluke the load will likely work to hit the pie plate kill area on a deer. Its also one reason I don't like to get fancy and shoot just for the neck or make overly long shots. Each to their own and I respect that.


DP