Can I trust my Magnetospeed numbers?

[JimSC]

here is a comparison between optical, LR, and MS that I did last summer

 

[D-4297]

Have a suggestion for you ; and please do not take it in any negative light , as it is not meant that way . Find a local shooter who can teach you about Brass preparation for competition use . I say this simply because I looked at your chart and graph, and the SD / ES was rather high across the board . This is usually a indication of Brass not being prepared with correct deburring , neck tension , etc. , etc. There are so many ways to get Brass prep wrong , but only a few ways to get it right . And it does have a major effect on load development .

 

[JimSC]

Have a suggestion for you ; and please do not take it in any negative light , as it is not meant that way . Find a local shooter who can teach you about Brass preparation for competition use . I say this simply because I looked at your chart and graph, and the SD / ES was rather high across the board . This is usually a indication of Brass not being prepared with correct deburring , neck tension , etc. , etc. There are so many ways to get Brass prep wrong , but only a few ways to get it right . And it does have a major effect on load development .

No offense taken but if you are referring to my post that was simply 20 rounds of ammo I loaded to test the accuracy of the Shotmarker's velocity info back when I first acquired the to see if it could be used to fine tune BC's I just loaded some 80 grain bulk bullets behind a middle of the range powder charges. I just happened to run into a friend who had a Labradar and he was kind enough to set it up for me. I am damn glad he did though because to me it proved an optical chrono set up on a sturdy tripod with sunshades at the proper distance is plenty accurate for load development. I also keep a MS sporter in my bag for quick spot checks to verify my scope DOPE.

I don't compete in SD contests anyway.I have a .223 80 grain load that shoots sub MOA consistently out to 800 yards. the ES last time i checked it was a 150 something ish.

 

[Doom]

How large of a sample size is needed to be able to draw meaningful conclusions from? I think the issue is time and money. If your barrel has a life of 2000 rounds and your loads cost $2 a round, is it reasonable to test in 20, 50 or 100 shot strings to have a sample size which might give stronger correlation coefficient and/or statistical confidence? Would that even be enough data?

Doom, let me ask you this. If you had a way to perform a controlled test, lab environment and a barrel that didnt wear out - you shoot 2000 shots of a match grade hand load. 2000 more shots exactly the same but .2 more powder, and repeated it increasing .2 for each 2000 shot string, do you think the scatter plot would show an average velocity precisely linear with the powder charge increase? Or would there be some variations (flat spots) like we see with 3 and 5 shot tests?

You've asked a question that is much deeper in detail than your basic assumptions. First off in designing such an experiment the goal is to change only one variable, in this case charge weight. Unfortunately in the case of multiple rounds being required that rule is violated because every bullet is different, every charge is slightly different, every case volume is different, every primer was different, every neck tension is different. Even the barrel is ever so slightly different. Most are small but they all contribute to velocity differences. Each variable that we cannot control would require that we determine the uncertainty that it introduces and requires that we attempt to quantify it if significant or ignore it if insignificant. If we don't then that variation shows up in the powder/velocity relationship. We also have to quantify the uncertainty introduced by each of the measurements (instrumental uncertainty).

If we take a cartridge/powder/bullet combination that has an approximate increase in velocity of 5 fps/0.1gr then at 0.2gr increments we would predict about 10 fps of increase. To keep the effect of the chronograph to a minimum it would need a total accuracy 4x greater than what we are trying to measure or an accuracy of +/-1.25 fps to minimize its effect on SD and velocity. That is about twice as good as a LabRadaR can do.

If we were to take your case of 2000 shots at each charge at face value for each load we would have a very good idea of the mean velocity and the standard deviation of velocity. Even if charge versus velocity is perfectly linear the test data would not in all likelihood be perfectly linear. In real world testing if that were to happen we would make the assumption that the data is not real but manufactured. NOTE: Charge and pressure/velocity are not necessarily linear but over a limited range can be represented as linear.

To the existence of flat spots. I have not heard anyone come up with a hypothesis or theory as to why a flat spot would exist. To do so requires that the energy input from the powder that should show up in the bullet is now going to either heating the case barrel or gases/residue, And with another increase go back to the way it was before. IS IT REPEATABLE? Did combustion efficiency get worse then better? Did the heat transfer suddenly get better then worse again? In science and engineering we call these types of effects discontinities. Nature doesn't work this way. It abhors discontinuities which is what would be required here.

When you test 3 or 5 or even more the flat spots you see in the test data are real because the data is the data. But they are not the result of the change in charge but are the results of the influence of the items listed above and the statistical probabilities associated with those influences and also with the limited sampling.

 

[CacheCropp]

You've asked a question that is much deeper in detail than your basic assumptions. First off in designing such an experiment the goal is to change only one variable, in this case charge weight. Unfortunately in the case of multiple rounds being required that rule is violated because every bullet is different, every charge is slightly different, every case volume is different, every primer was different, every neck tension is different. Even the barrel is ever so slightly different. Most are small but they all contribute to velocity differences. Each variable that we cannot control would require that we determine the uncertainty that it introduces and requires that we attempt to quantify it if significant or ignore it if insignificant. If we don't then that variation shows up in the powder/velocity relationship. We also have to quantify the uncertainty introduced by each of the measurements (instrumental uncertainty).

If we take a cartridge/powder/bullet combination that has an approximate increase in velocity of 5 fps/0.1gr then at 0.2gr increments we would predict about 10 fps of increase. To keep the effect of the chronograph to a minimum it would need a total accuracy 4x greater than what we are trying to measure or an accuracy of +/-1.25 fps to minimize its effect on SD and velocity. That is about twice as good as a LabRadaR can do.

If we were to take your case of 2000 shots at each charge at face value for each load we would have a very good idea of the mean velocity and the standard deviation of velocity. Even if charge versus velocity is perfectly linear the test data would not in all likelihood be perfectly linear. In real world testing if that were to happen we would make the assumption that the data is not real but manufactured. NOTE: Charge and pressure/velocity are not necessarily linear but over a limited range can be represented as linear.

To the existence of flat spots. I have not heard anyone come up with a hypothesis or theory as to why a flat spot would exist. To do so requires that the energy input from the powder that should show up in the bullet is now going to either heating the case barrel or gases/residue, And with another increase go back to the way it was before. IS IT REPEATABLE? Did combustion efficiency get worse then better? Did the heat transfer suddenly get better then worse again? In science and engineering we call these types of effects discontinities. Nature doesn't work this way. It abhors discontinuities which is what would be required here.

When you test 3 or 5 or even more the flat spots you see in the test data are real because the data is the data. But they are not the result of the change in charge but are the results of the influence of the items listed above and the statistical probabilities associated with those influences and also with the limited sampling.

I thought this is what you would say. Thank you for taking the time to provide such a thorough answer. I know everyone has their own opinions on this, but I believe what you’re saying to be true and accurate. I also believe there are lots of correlations observed by shooters. Some of those correlations may be too flawed for some of the many reasons you stated, but there’s no mistaking that some shooters manage to sift through the wood pile of information and shoot match winning scores again and again. I think what we have in precision rifle shooting is more of an art than a science despite all the numbers and data we deal with. The human brain can, through experience, piece together tons of data points coupled with observations, trial and error and it’s more akin to painting a picture than a research lab.

 

[Doom]

I didn't start shooting and reloading until about 13 years ago but have spent a lot of my time studying what is going on with reloading, ballistics, and testing. I started out with Dan Newberry's load development and found that it worked. No chronograph, just a target and find a POI that seemed consistent for neighboring charges. NO Chronograph. Test was the entire firing system including the shooter. System worked great for me. Smallest possible group? I don't know. But with the availability of the Magneto speed and LabRadar Scott Satterlee came up with his Velocity Ladder and it worked for him. All of a sudden we were looking for flat spots and smallest SD's. Pick flatter powder charge range (one shot Ladder) and find seating depth. Scott has since worked his system differently and picks a charge, finds a seating depth and further refines his charge. There are others that say pick a charge and find a seating depth.

When you look there are known "nodes" for a given cartridge they tend to be roughly the same independent of how they were arrived at. I personally think, but haven't tested that you can literally pick a charge and there will be a seating depth that will work consistent with pressure limits and maintaining sufficient case fill.
Somehow we find something that works. It makes me think that we often overcomplicate this process, often based on insufficient data or incorrect analysis.

As for me, I'll stick with Dan's system because I doubt I can outshot the results. Chronograph? I use it to see how consistent my reloads are for velocity and to verify my drops.

 

[Webster]

That is the question.

in my load development I’ve been using a new magnetospeed. So far I’ve only been testing for SD/ES. Next step is to do some seating depth testing. I have a number of questions and concerns and am looking for help in finding the best path forward. I’ll number them to keep it simple:

1. using two powders, one bullet over 15 different loads, I’ve had one (lowest velocity) group with an SD of 0.8 and ES of 2.0 and 6 groups between 4 and 8 SD. Can I trust these magnetospeed numbers going forward? NOTE: my Magnetospeed did slide forward on the barrel several times requiring me to slide it back and tighten it some.

2. related to the first question, if I can trust those numbers, is the consensus wisdom to then do bullet seating depth testing WITHOUT the magnetospeed attached and test purely for groups And impact locations?

3. I may look for a better mount, like Wiser, but currently I test with an adjustable front bench rest and haven’t seen another mounting option that would work with that. Also I don’t want to spend more money if I’m just going to end up with a Labradar.

4. Will a Lab Radar work even when you have to shoot through a metal tunnel? Many shooting ranges require you to shoot through these. So will the rifle barrel and Lab Radar fit into the same 2 foot wide space and work?

Comments - I like the convenience of the Magneto Speed and the ability to import the data to a laptop. I am not impressed with the cheap plasticky mounts and spacers. It does not meet my expectations of a $300 product. More in line with some knock-off Chinese copy you might buy from Amazon. Still like the product overall, but not if I can’t trust my load development process.

You never described the rifle and what it's used for. I hope your not going to tell us it's an off the shelf deer hunting rifle. To repeat if the groups are small it doesn't matter what the ES is. Buying more chrono's to compare their accuracy just means you have more numbers that are not related to accuracy. The top shooters just look at targets and interpret the results. Now you want to test seating depth and collect meaningless chrono numbers.

 

[Badhabit]

This might get me banished but I have 2 mentors that have coached me through my journey into becoming a better shooter and reloader. One of the first things I was told was a chronograph and borescope was the two worst things to purchase. Well now I have 2 chronographs and a borescope. And no longer use either. The scope did teach me how to properly clean and the chronographs taught me it was a waist of time money and frustration. The very first thing I was told was to let the target tell you. Then I go read all the forums and start second guessing myself and everyone else. Well after thousands of rounds on fired I had to apologize to them and go back to letting the target do the talking. Now I will say they can show you a problem with your process but so does listening to them old timers trying to teach us kids something.

 

[D-4297]

No offense taken but if you are referring to my post that was simply 20 rounds of ammo I loaded to test the accuracy of the Shotmarker's velocity info back when I first acquired the to see if it could be used to fine tune BC's I just loaded some 80 grain bulk bullets behind a middle of the range powder charges. I just happened to run into a friend who had a Labradar and he was kind enough to set it up for me. I am damn glad he did though because to me it proved an optical chrono set up on a sturdy tripod with sunshades at the proper distance is plenty accurate for load development. I also keep a MS sporter in my bag for quick spot checks to verify my scope DOPE.

I don't compete in SD contests anyway.I have a .223 80 grain load that shoots sub MOA consistently out to 800 yards. the ES last time i checked it was a 150 something ish.

I was posting to the Original Poster . Thought it read clearly enough to indicate so

 

[Sniperhandle]

This might get me banished but I have 2 mentors that have coached me through my journey into becoming a better shooter and reloader. One of the first things I was told was a chronograph and borescope was the two worst things to purchase. Well now I have 2 chronographs and a borescope. And no longer use either. The scope did teach me how to properly clean and the chronographs taught me it was a waist of time money and frustration. The very first thing I was told was to let the target tell you. Then I go read all the forums and start second guessing myself and everyone else. Well after thousands of rounds on fired I had to apologize to them and go back to letting the target do the talking. Now I will say they can show you a problem with your process but so does listening to them old timers trying to teach us kids something.

You need a chronograph if you are going to shoot competitions, You need it for drop charts Etc.

 

[Badhabit]

You need a chronograph if you are going to shoot competitions, You need it for drop charts Etc.

We do shoot competitive benchrest, short-range and long range . Matter of fact I just won a 1000 yard match with a barrel that only had 46 rounds through it and never been chronograph. And drop charts need varification. I would never really solely on a chronograph and ballistic program. Im not trying to be argumentive but believe me when I say I've been there done that. I've been enough ocd to use 3 chronograph at the same time. Have a good day I'm done rambling

 

[Webster]

You need a chronograph if you are going to shoot competitions, You need it for drop charts Etc.

The target tells you what the drop is.