Tag: chronograph

September 29, 2022 – ‘Tacticool’ Thursday

September 29, 2022 /

Rolling around to another Thursday, today I am going to finish off the conversation that I started last week on the ballistics of my reloads for .357 magnum. This was my first trip to the range with my chronograph. Look at all the junk I have to take, I am thinking of getting a larger range bag since mine is chronically full.

Since I provided the raw data last week, I am going to skip entering it this week. But, below I am going to provide the calculations from that data. What I can tell from the data is that charge weight makes very little difference in velocity unless it is the highest charge,

I think that it is worth pointing out a couple of things. Given the choice of charges and based on this data, I would choose the smallest load of 5.8 grains just based on performance. This actually ignores one variable that I didn’t test and that is accuracy. It is possible that one of the four charges is more accurate than the other three. The truth is, that would be the true choice. So, I will have to test that in the future.

5.8gr5.9gr6.0gr6.2gr6.3gr
Velocity9499329259431055
3 sigma327284161131168
Energy316305300312391

What I didn’t get was close to the published velocity. The data suggested that I should get 1050-1150 fps. It could be because I substituted components. I really don’t think so, but it is possible.

Now, theirs was measured on a 10″ barrel. However, I had a 16″ barrel and would expect to get similar to better velocity. To show what a difference barrel length makes, I also shot some factory .38 special on my range trip.

2″16″
17841031
27511094
37731131
47881131
57621154
67831159
77621143
87781143
97761113
Average7731122
3 sigma35117
Energy172363

What is the difference between .357 magnum and .38 special besides case length? It is pressure of cartridge during ignition 35,000 vs. 17,000 psi respectively. What I didn’t say with this data is the bullet is slightly lighter at 130 grains. Granted, this is a lighter bullet but the equalizer number is the energy.

Looking at the energy of 363 ft*lbs for .38 special versus 391 ft*lbs for .357 magnum I would deem this load as inadequate. Energy and velocity are not everything there is something to be said for accuracy as well. At least on the surface, I am definitely not getting the full potential of .357 magnum with this load combination.

If you remember a pound of powder is 7000 grains. And if I loaded 100 rounds averaging about 6 grains each for 600 grains I still have 90% of a pound left. It is good enough to make plinking rounds but given the choice, I would look for another powder.

End Your Programming Routine: I have done this exercise with several different powders and bullet weights. So, expect more of this in the future. Given our current state of reloading component shortages, it is unlikely that I am going to readily find a replacement to try any time soon. Of course, I am going to focus on what I currently have to get the most information on what I have on hand. I found the process enlightening, I hope that you did.

July 7, 2022 – ‘Tacticool’ Thursday

July 7, 2022 /

During the holiday weekend, I finally got some time to mess around with my chronograph. My initial test was not very favorable. I wasn’t able to get any readings the first time I messed with it (before vacation). But, I spent some time last Saturday to try and figure out what was wrong.

Today, I am going to talk about math again. I know, I know it is less fun than watching paint dry. I want to talk about looking at the dataset, calculating average with standard deviation and energy as a result of my velocity measurements. Should be fun.

A quick aside about math. We use math to describe physical behavior. I am not just solving problems for problem sake, like sudoku. I am looking at the data so that I can compare certain behaviors like 1) how consistent is the rifle 2) is a lighter faster pellet better than a heavier and slower pellet (when I look at the energy)? 3) Does pellet shape make a difference with the same weight?

Maybe it is the cold medicine talking but I came up with this idea this morning. Art and math are very similar. Both are attempting to describe life in different ways. One is by representation and the other is by description. One is subjective by interpretation and the other is deterministic, using concrete laws and methods. What I am trying to say is that you don’t have to know how to do math (like art) to appreciate what it does for us. Unlike art, I can show you how I got to my final numbers.

I went about this in a pseudo scientific way. I shot a bunch of times and recorded the data that I liked the best. In all seriousness, I need to spend more time with this device to understand what a good reading looks like. However, I had a lot of readings that were similar and some that were way off the reservation. I threw out those measurements as outliers. In science, those would have qualified reasons to be excluded. There are mathematical ways of proving those outliers, but that is super advanced math. That being said, I am just going to ignore them as bad measurements.

Here is the dataset I ended up with (feet per second or fps). I think you can see why excluded the results in the images above.

  1. 942
  2. 946
  3. 966
  4. 959
  5. 953
  6. 952
  7. 973
  8. 947
  9. 951
  10. 966

The first thing that we need to calculate is the mean. Another word for that is average.

What I have calculated is the average pellet velocity is 955.8 fps. We will need that number to calculate the standard deviation. It looks reasonable so far but I think that I will save that calculation for next week. Before I end, I will plug the average velocity into the energy calculation because that is the number I am looking for to compare everything in the future.

End Your Programming Routine: If I assume that the outlier measurements were problems measuring and not exactly irregularities firing the rifle, I am pretty impressed with the consistency of the velocities. I did ignore values that did not change after firing. Again, I don’t know if the velocities were the same, but I assume that the pellet did not measure. Give me some time with this device and I can have more confidence in the actual results.

May 12, 2022 – ‘Tacticool’ Thursday

May 12, 2022 /

I hate to start out this way, but I didn’t make much progress with my chronograph work. I did give it a shot, but I couldn’t get a viable reading. Mind you, I only shot some pellets in the basement.

My current operating theory is that the light is too dim and the projectile is too small to register. I understand this device to work with two optical sensors. I think that it sees the projectile pass over each sensor and then calculates the time difference. So, if it is not being seen then it doesn’t calculate.

There were some warnings about using it in low light, and this situation definitely fits. My particular model actually has LED lights on the background reflector (the white plastic strips). I think that the lights are an attempt to extend the useful light and projectile size. Yet they didn’t seem to work on my initial attempt.

I have plans to test my son’s nerf gun just to see if something will register before I get too carried away. If I can get some measurements, then I can experiment with the light conditions. There is also technical support because it is supposed to work with pellets.

End Your Programming Routine: Due to the fact that I am out of town this week, I am not going to make any progress while I am gone. I haven’t totally decided but this would be a good weekend to also go to the range. Likely, since I am just getting back I will need the time to do stuff around the house. But, I could probably squeeze in some trigger time outside, if the weather permits.

May 5, 2022 – ‘Tacticool’ Thursday

May 5, 2022 /

It’s been a while since I did some math. For those of you that don’t remember, don’t care or are not interested, that is fine. These are real experiments and real life applications of physics and mathematics. Guess what, they are pretty simple as things go too.

I picked up a chronograph this week. This is a tool that measures how fast a projectile is travelling. From that, I will be able to calculate energy and measure the consistency of my reloads. I think that I am going to get some interesting data from this. Energy is the real life equalizer when comparing different calibers like fast and light versus slow and heavy or bullet to bullet size.

Sir Isaac Newton figured it out a long time ago. The formula for kinetic energy is 1/2 mass * velocity * velocity. At the risk of being boring, mass and weight are not the same thing. Mass is really how much space something takes. Weight is mass plus gravity (really mass times gravity). So, when we measure something in pounds or grains, we need to divide by a constant of earth’s gravitational pull as well. If we were to use the metric system, we wouldn’t have to do this extra conversion.

This describes the energy calculation above.

Essentially, all I have to do is know my bullet weight in grains and measure my velocities and plug it into the formula above to calculate energy. I am going to demonstrate some more math later when I get more data but I will talk about it when I get there. I don’t want to get too heavy too quickly.

You don’t have to understand my math to use it, just plug in values into the formula and calculate. My math was proving that the formula for kinetic energy was applicable to my situation. The actual scientific unit for energy is a Joule. You will have to convert all those units to metric to look at it in that unit. That is a whole different post, but it can be done.

Here are some quick examples for perspective

  • 22LR – 130 ft lb
  • 9mm- 355 ft lb
  • 357 magnum – 583 ft lb
  • 30-06 – 2913 ft lb

The above are just examples with nominal weight bullets and velocities. Energy can change with different weight bullets and particularly more velocity (because it is a squared value). This mean shooting a 22lr from a handgun and a rifle are going to have dramatically different energy values because in theory, you are going to get a more efficient powder burn from a rifle and have significantly more velocity.

I do have some planned experiments in mind first. I want to measure velocities of my pellet rifle. The first thing I am interested in is how consistent are the velocities shot to shot. The second thing I am interested in are how much the velocities change with different pellets both weight and design. I am also interested in velocities at the muzzle vs the target or how much loss there is over distance.

I have some other experiments planned for my BB/Pellet rifle. It takes 10 pumps to get to full power. I want to see the velocity difference in each pump and the consistency of that particular rifle. Or said another way 1 pump = x fps, 2 pumps = y fps, 3 pumps = z fps. I plan to use that data to tell me how much difference there is (or isn’t) for follow-up shots and accuracy.

Finally, I want to do some checking of my reloads. I want to know how consistently I am making ammunition. I would be interested in checking factory loads and comparing my work to the published data. There is a ton on science and information that can be gained from this tool.

I definitely don’t see myself using this each time I go to the range. However, I do see myself using it until I get a comfort level of consistency. Once I establish a baseline that seems to be predictable, I will be an informed shooter with data rather than what I think I know.

End Your Programming Routine: It has been a long time since I tried to type math equations into a word processing program. I had to do it routinely in college, but I really haven’t had much use since then. Word has improved quite a bit in twenty-five years. I know, it is kind of hard to get excited about reading someone else doing math, but for me it is like reviving old brain cells. I wont have a data set this week, but soon.