CED M2 Chronograph

I think you're confusing consistency with velocity, if that makes any sense. You make a good case for 'consistent velocity' as being important to accuracy, and I can agree with that in the sense that if you aren't consistent, you don't know where the bullet is going, and that's the very definition of lack of accuracy.

But is any one velocity, 1250 fps for instance, more accurate for a given combination of bullet, rifle, powder, lube and patch than say 1300 fps? I haven't seen any evidence to support that assertion. But maybe I don't understand your argument; maybe that's not what you mean when you say velocity is important to accuracy.

Or put another way: If I manage to obtain, say, a 5 shot 3/4" group at 100 yards with a given combination of variables, and then determine that all 5 rounds were measured at, say 1500 fps, and then let's say that I reduce powder and projectile weight to get another combination of variables that measure 1500 fps, consistently, does it follow that the second combination will necessarily produce 5 shot 3/4" groups as well? There may well be a second combination of variables that produce that accuracy, but I submit the velocity won't be the same. Or will it?

Velocity can be an indication of how closely the components of a given round matched those of another round, but in my opinion that's all it is: a metric. Perhaps we're actually in violent agreement.
 
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I'm not confused about barrel harmonics and how velocity affects it. Consistent velocity equals repeatable accuracy, but the barrel hamonics must also be tested for each bullet type/weight/length fired by reading the target results so that the optimum velocity range can be found. It's basically working up a load using a chrony and introducing velocity into the accuracy equation. Velocity is usually simply measured by the amount of powder loaded, but the FPS isn't known for when switching powders and neither are the deviations known. They are only guessed at without knowing about the amount of human error. Using a chrony is just a scientific and provable method of determining what the velocity is without simply relying on the amount of powder loaded. ;)
 
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arcticap - apologies. I edited my latest post to add another paragraph while you were posting your latest. It appears from the sequence that your latest responded to my latest, but readers should know I changed mine.
 
I edited for several minutes too.

I agree that consistent velocity can produce consistent inaccuracy. But that's why I mentioned above that velocity isn't measured in a vacuum. It's used as the reference when shooting groups at targets to determine what speed the accurate or inaccurate load was traveling at. It's simply a reference point so that there's a standard for when switching powders, or different lots of powders to reformulate the next optimum load, especially for competition shooters.

When trying to configure a new load or match a successful load, one of the things that can almost be guaranteed to be achievable is the velocity. Then at least there is a basis to tinker with a load to try to successfully match the velocity and accuracy of a previously accurate load, even if the powder has changed.
 
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If the projectile takes a different, longer path, for instance, a diagonal between the screens (either horizontally or vertically or both), then the calculation will be in error by the amount the actual path distance varies from the assumed path distance.
Click to expand...

That is the theory. In practice the difference is insignificant. I find the sensors work best when the bullet is near the bottom of the "V" of the skyscreens. I set them up to be shooting about 6 inches above the sensor apex (bottom of V).

You normally align the screen rail fairly parallel to the direction of the target as you do not want to be hitting one of the screen arms.

I would estimate at most you could be 3" off horizontally from one screen to the other. But when you calculate the difference in length it is only 0.77% more going at that diagonal. At 3,000 fps that would read about about 22-23 fps less than if it was traveling through both centers exactly. For me, 23fps is insignificant for my purposes.

Since I am intending to compare loads during the same shooting session then I would estimate my shooting through the screens only varies by about 1" horizontally, if that much, during the same session. That reduces variance from diagonal paths to about 7fps.

It is a mistake to try to be too precise with a consumer grade electronic instrument under field conditions. There are many other variables that have much more effect on variance than the chronograph: temperature, handloading technique, powder measure tolerances, etc.

For instance most popular powder measures have about a 0.1 gr variance. With a light handgun target load of 4.0 grains that is a 2.5% variance alone. Or, many rifle powders have been shown to vary as much as 100fps (at around 2,800 fps nominal) due to wide temperature changes (Hodgdon Extreme line of powders is designed specifically to minimize temperature variation in burn rate).

Like any tool you have to understand what a field chronograph is designed for an use it within those parameters. They are used widely in the shooting community and I have never heard of any brand being known for significant errors. My experience with the CED M2 is it either gets a good reading or it tells you it can't determine the speed at all. Some chronies have three screens so it takes two or three sets of readings and can determine if one of them is out of line.

I bought a boatload of reloading equipment before I considered getting a chrony. They certainly are not essential, but they do you give you another way to measure your ammo characteristics and compare them among others you measure under similar conditions.

Just a comment on the speed and accuracy discussion. Speed itself has nothing to do with accuracy, but consistency of speed usually does at some point. However, when a bullet drops below the sound barrier it can introduce greater variability. So a chrono can help you determine whether your bullet will remain supersonic or maybe dropping below the transition range and more likely to be less accurate.

Chronos are also used at some matches to determine the "power factor" of each participants loads. So it is handy to have one to make sure your loads will pass the testing before you show up on the day of competition.

If one is more interested in lab work than the shooting range then these are not the instruments for you and you should pan to spend thousands and not a couple of hundred dollars.

Note: I have purposely not identified every possible use of a chronograph in the field of recreational, nor every possible factor that may cause variance. I have mentioned the ones I find interesting or notable. I assume others can point any others that are relevant to them. :)
 
I have an older CED chronograph. When I bought mine they had serial connections. I love it for what it does. I just wish it was setup with a memory card of a USB connection. I have never had a need to calibrate it. I tested it with factory ammo and a factory gun. I also tested it with subsonics and a suppressor. If it is off by 50fps, I would be surprised.

As far as use:
I think the #1 use is for competitors trying to have the least powerful load and still be legal for that level of competition.

For me it is more the scientific study of ballistics and reloading. There are so many different variables. One day the target shows, I am shooting great and the next day things are off. Was it me, or did I do something to my loads?

When I was trying to develop a subsonic suppressed 308 round. The first round warms the barrel and screws up the rest of the test, UNLESS I know what the first round should chrono in a warm barrel in which case I can guess at what might be working and what is going to be way too fast or slow. Then I can come back and do cold barrel testing. (This really means I need two loads. One for first round and one for everything after the first round.)

When I was developing 45Super loads, some of the time things looked good on paper, but the load didn’t perform well (not up to speed). I don’t know why, but that is what happened.

When looking at Black powder theory, I hope to re-adjust my load (back them down) to a load that has the most accuracy with the most velocity. Or maybe I will be going for the load with the most velocity and acceptable accuracy. It really depends on some other tests on terminal theory. (BTW, I am accurate for me, with irons at 100 yards, but I know I am past max load for my gun. This is a compound screw up, that would need 500 words to describe.)

Then there are the tests on terminal theory. I have gel. Where I could shoot gel, was a limited distance range. If I am going to test 9mm or 45ACP hits at 100+ yards, I will need to run the ballistic calculator for velocity numbers and then develop a load that simulates what a 9mm or 45ACP should be doing at 100+ yards.
 
Man! Never did I expect that asking a few questions would produce such a flurry of information!

First things first . . . . NWPilgrim and others who may have misinterpreted (or not) my original questions . . . . . I am not nor ever will make fun of or "knock" anyone who uses a chronograph nor for anything else . . . I'm not cut from that cloth . . . . . my questions, however poorly worded they might have been or possibly misunderstood were not meant to upset anyone. I have never had any experience with a chronograph nor even seen one used other than in pictures. To clarify my comments about not being "scientific" . . . I'm not! I'm a "right brained" fella who always had problems with chemistry and the other sciences such as physics - just not my "bag" and thank goodness I didn't need a lot of science for my degrees as I would have been in trouble. :D I was always under the misguided idea that what they tested were the fps. After reading the many posts, I see how wrong I was in their application and the various things that those that use them are concerned with and the data they can produce.

My questions were basically aimed at "Doc" as he and I have often gone back and forth on posts in regards to a number of topics and I know he is a person who likes to "explore" the why and how of things - whether it be rebuilding a pistol or designing a new range box. I personally learn a lot from the others that post on this site and their experiences. It's evident that each of you use a chronograph in your own way to collect data and try to make improvements in what you are doing - whether it be in regards to C&B shooting, cartridge shooting, powder loads, primer ignition or slugs, etc. with different variables. I honestly think it's great! Basically, I was trying to find out "why" a person uses one and what they can tell you. I was not doing this in a accusatory tone at all - I was curious and had questions. I probably will never own a chronograph as for the type of shooting I do - plinking, cans, targets - none of it in competition, I'm sure doesn't warrant the expense. I do "experiment" though with various powder loads, patching material, lubes, etc. as I like to see the different results and which one works best. Those of you that have a scientific tendency just take it a step further and use the technology available to answer the questions you have. I appreciate that as your findings help those of us who don't have the knowledge or equipment to learn more and perhaps change some of the things we are doing to get better results.

I enjoy this board because of the fact that others are willing to share their knowledge with each other. There is a great group of fellas here and I have learned a lot that I didn't know, even after having shot BP for 45+ years. The one disappointing thing though, is when someone takes great offense at someone else's thoughts or opinions and jumps on them with both boots and spurs. We all can learn from each other in a respectful way.

Once again, I apologize to anyone that my questions may have stirred up as anything I said was not intended to ruffle any feathers or criticize anyone who uses a chronograph and the information they can provide. I thank all of you who shared your comments as I now have a better understanding of what they are used for and why they are used. Many thanks! Sincerely, BB :)
 
BBB

I agree about 300 percent with everything you said...You are absolutely correct, especially all the nice things you said about me....:D
 
Doc, I have not cast my own bullets. It is something I have wanted to do, but I just have not had the time, location and money to do it. I did have someone do some custom casting for me a few years ago. That allowed for a different experiment.

bedbugbilly, don’t apologize. I didn’t get the hole chronograph thing for years. Then I got one and started munging the data. The more I played with the data the more I “think” I see patterns. If I can just get a little more data, I might have a useful theory to two to put my name on.
 
Sorry for the confusion Bedbug. My earlier post should have been addressed to Mykeal and not you. Mykeal pointed this out and I apologize to you for posting to the wrong person.

I agree this has been very informative thread and appreciate Doc's experience and posts, too. Keep asking those questions because that is how we all learn!
 
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