johnsons1480

I use the CED Millennium 2. I like it, but I sure wish that Magnetospeed had been out when I was in the market. The CED does have relatively cheap replacement parts as well (ask me how I know lol)

RobertSubnet

I have a Beta Chrony by Shooting Chrony. It works well but I wish it held more shots. It holds 60 shots - 6 strings of 10 rounds.

Whatever you decide upon be sure to get a sturdy tripod - sturdy meaning it has some weight to it. A Bogen 3001 or something comparable is an excellent choice. I see people use light-weight tripods (IE "Slik") which may be easy to carry but once any wind blows their chrony gets knocked right over (those screens are very good at catching wind!).

JGFLHunter

How do chronographs actually work? When you put the chronograpgh 15-20 feet away from the muzzle, what information does it give? For example, does it provide 50 or 100 yard velocities? How do you figure out the energy at certain distances? I've looked at some youtube videos but I didn't find anything helpful besides setting it up and someone shooting.

ckell

It sees the shadow of the bullet as it passes over the sensors. The first sensor turns it on, the second turns it off. It calculates the time between.
I suppose you could set up a back stop at 50 yards or what ever distance you want. But if you are off a little you could hit the chrony.

Bullet Weight say 168 gr times Velocity squared say 2600 fps divided by 450395.

168x(2600x2600)/450395

168x( 6,760,000)/ 450395

1,135,680,000/450395

2521 fp of energy

Ridge Runner

a chrony can tell you things about your load that you will never know any other way, if you have the knowledge to interpret the info it gives you.
your ES, your SD, if you are close, at or above max pressure. but you have to know what to look for. I know to do what I do with a rifle, a chrony is a must have, without knowing your velocity, hitting a target at a grand is just grasping straws. a chrony can give you the info you need to set up your rifle to easily hit your mark at distances you never thought possible.
RR

RobertSubnet

I am doing this from memory so I may miss some things. My Beta Chrony will:

Report the bullet speed in feet per second.

If you save a group of shots ("a string") you can recall:
*The string number
*The highest velocity (in feet per second) shot of the string
*The lowest velocity shot of the string.
*The average velocity of the shots in the string
*The "extreme spread" - the difference between the highest and lowest velocities
*The velocity of each shot in the string.

What I use this data for is:

1. Compare a string against a particular target. IE: String #2, Target #2. How is the grouping?
2. Compare the "extreme spread" of the velocities of my loads vs. factory loads. (I am happy to report that my hand loads beat factory loads. That is the velocity difference of my loads is lower than factory rounds).
3. Check the average velocity against published data - are you close to published speeds?
4. Check for pressure spikes or rounds that are consistently faster than they should be.
5. Check the consistency of your rounds - are they close in velocity?

These are the things I typically use my chrony for. Others may have additional suggestions. When mounting a target to a frame I will write a target number on the target so I can correlate the target number with a string stored in the chrony - use a notepad for this.

The display/controller unit of the Beta Chrony uses a 10' cable so you can place the unit next to you. When shooting you can immediately look to see the velocity of the just fired round. Some chronographs have this display unit on the chronograph. I have not used a unit such as this but I would think that would be hard to see. With my Beta Chrony I can put the display/controller unit right next to me so it is very easy to see the velocities and control the chronograph from the shooting bench.

Another thing I will be using the chronograph for is load development. My 30-06 is a bit too powerful for me - guess I am recoil sensitive after all. Instead of selling the rifle for a .270 I have found a load that sends a 30-06 round at speeds similar to that of a 30-30. I think the powder is H4895. Anyway not want to completely gimp the 30-06 round I will start with the slower speed and work my way up to the point of where I begin to flinch - checking the velocities and making notes along the way. Eventually with the aid of the chronograph I will find the load that I am comfortable with.

Just some thoughts. I hope they are helpful.

RobertSubnet

RidgeRunner what is the standard deviation used for? That is a piece of data I am not sure how to use or what to do with.

Thanks.

Big Uncle

It is one of the most useful indicators. Very simply the standard deviation is the normal (not just the highest and lowest) distribution of data points from the average. The lower the SD the closer the points are to the average. Think of it as a measure of consistency.

Small SD numbers tell you that your velocity is fairly consistent, and high SD numbers tell you that you have high variations in your velocity readings.

The math behind the SD calculation is reasonably simple. The variations are squared to make all of the numbers positive, then the square root is used to bring the numbers back, and a standard (average) deviation is calculated. If this is not done the negative numbers (from the mean) offset the positive numbers making the result useless.

To boil it down - small SD is good, big SD is bad.

RobertSubnet

Thanks Big Uncle! I can see how that would really help when determining consistency.

homers brother

I set up my Chrony Alpha (@ $100) at 10' from the muzzle. It provides you an equivalent "muzzle" velocity. In order to determine velocities downrange, you're going to need some kind of ballistics program to plug the velocity into, along with the BC of your chosen projectile and other variables recorded when you fired the string (some use mm/Hg and altitude, I use Density Altitude). Some ballistics programs will give you a calculated energy value, but (IMO) that's a discussion that isn't relevant here.

In the context of reloading, you shouldn't worry about collecting any of that data (or not). If you're reloading for accuracy, neither speed or energy as a single value are at all relevant. You're comparing each single data point for velocity against the other data points.

What the chronograph gives you is exactly what RR and Big Uncle have already described. Consistency is the key. Extreme Spread and Standard Deviation are the metrics you should be focused on. Bottom Line: Smaller numbers in your variations are better. Think of it this way: A load with an average velocity of 2800 fps (+/- 100 fps, with a SD of 40 fps) is not as consistent as a load with an average velocity of 2800 fps (+/- 25 fps with a SD of 15 fps). Therefore, the latter has more potential for accuracy than the former. The chronograph will tell you precisely what those variations are.

You can spend as much on a chronograph as you're willing to spend. The Chrony Alpha is probably the least expensive version on the market, and I've found that while it might miss capturing a shot from time-to-time, I've probably saved what it cost me in conserving time and components in the first couple years that I used it. It lacks some of the "conveniences" (remote readout, etc.) that other models might offer, but I've not found that to be much of a liability.