PACT MODEL 1 CHRONOGRAPH
I have been using a Model 1 Chronograph now for 3 or 4 years and thoroughly enjoy it. For years I had guesstimated velocities based on
numbers from the manuals. This approach works but if fails to tell you much about your particular load.
The Model 1 is the most economical model that PACT makes, it does not do everything the bigger models do, however for the average shooter, it is great.
It will record the velocity of up to 20 consecutive shots. Based on those velocities, it will show you: Low & High as well as calculate
Average Velocity, Extreme Spread, Standard Deviation and Average Deviation.
I am not a mathematical wizard so I won't attempt to explain too deeply.
Low and High are obvious, and are usually interesting numbers.
Extreme Spread is also pretty easy to figure out.
Standard Deviation, a measure of dispersion in a frequency distribution, equal to the square root of the mean of the squares of
the deviations from the arithmetic mean of the distribution.
Average Deviation, (mean deviation) a measure of dispersion, computed by taking the arithmetic mean of the absolute values of the deviations
of the functional values from some central value.
The "Deviations", what I comprehend, measure blah, blah blah blah central value.
In terms I do understand, Standard Deviation is accurate when looking at a large quantity of numbers but when you're talking a group of 5 to
10 shots, Average Deviation is a more accurate number. Low Average Deviations are a good thing.
Ok, now that we fully understand "Deviation", as we fire groups across our chronograph, our favored load should be one with a very low Average Deviation.
In last month's feature article I discussed the dramatic differences switching components could make. With a chronograph, they become even
Pact is not the only game in town, it just happens to be what I own. I chose it for several reasons. First and foremost, I did not want the
equipment in front of my barrel, one sneeze and, well you get the idea. The Pact has a unit that sits on the bench and the only thing the
bullet flies past are the sky screens. Having the unit on the bench also allows readability. It is right there, no squinting, no getting up
to go look at it.
The Skyscreens are big, and set up, they basically form a V shape that is 12" wide at the top and 14" tall in the center. You can mount them
on a board or purchase the accessory bar on which to mount them. The accessory bar can be mounted on a regular photo tri-pod, which makes a pretty handy surface. At the hundred-yard bench, you can shoot at several different targets and not have to move the screens. The screens
are connected to the unit with 2 cables, one for the "Start Screen" and one for the "Stop Screen". The bar and screens make the system a little
cumbersome, so you have to set it up at the range. I have not found an alternative approach yet.
Operation is simple, turn it on, wait a couple of seconds for it to initialize and you're ready to go. When done with a string, simply
review the fields by pressing the "Review" button. It has an "Edit" button to remove bogus numbers. For example; you set the screens too
close to the bench and get a muzzle blast reading or whatever. I only recall using the "Edit" button a couple of times but it worked.
The whole system runs on a 9 volt battery, yep just like the one in your garage door opener, which you will probably have with you at the
range, should you ever do something dumb, like forget to make sure you have a fresh battery in the unit. Of course none of us would ever do
In summary, this article is not intended to compare units. It is simply to tell you how the Model 1 works and what I think of it. If I lost it
tomorrow, I would buy another just like it. The system does what it claims it will do and I enjoy having the data available on which to
base my loading decisions. Quality, price and functionality make it a great piece of equipment.
Copyright Centerfire Central, LLC
Copyright Centerfire Central, LLC 2004