Getting the Most Out of Your Chronograph Data--Temperature variables.
Hi all and welcome back to our short form blog posts on long range shooting and firearms training. These posts are meant to be brief thought provoking snippets to jump you ahead whether or not you are planning to attend one of our firearms training courses.
It is debated, mainly amongst beginner long range shooters, as to whether or not a chronograph is necessary to get started. For us at rangetech.us we feel that they are a crucial piece of information gathering technology that you should have whether or not you own a Magenetospeed V3, Sporter, or the new Garmin Xero C1 Pro which we are now taking back orders for. We personally use the Magnetospeed which we have owned for nearly 9 years if memory serves us correctly but we will add the Garmin once we see how product quality control is overall. (Never trust a brand new product to market)
Getting at the gist of this post though...gathering velocity data...particularly in colder or hotter temperatures.
In a recent test of my new Mission Silencer Suppressor on my LMT Defense 224 Valkyrie rifle I noticed some very slight decreases in velocity between short strings of fire.
Here's an example to show you and what I want to point out to you is the anomaly we see with shot 03-06 (Shot #6 of current string)
Clearly we have good consistent velocity readings generally speaking so why did number 6 shot dip 20fps? The answer is of course that the ammo and powder were allowed to cool between shots 5 and 7 which allowed the marginally temperature sensitive CFE 223 powder's developed velocity to vary downwards.
The next three shots taken several seconds apart show the results of temperature stable conditions in which the warm chamber was allowed to raise powder temperature.
But let's go back little further to demonstrate the differences we see with even more clarity. In the first of this string of shots we see a much greater difference in velocity because the rifle and ammo were allowed to sit in the freezing temperatures before I shot the rifle. Clearly shot number 1 demonstrates a significant drop win velocity but what does this mean to the long range shooter?
It means that anytime you go out in lesser or higher temperatures without taking into account these temperature variables your chances of making a cold bore shot are dependent on luck past a point. Personally, I don't like relying on luck. I prefer knowledge.
To reiterate, what we have displayed here is a story of my shooting that day. I went out in cold temperatures, allowed the rifle and ammo to acclimate to the conditions as I ran other tests, set up the rifle with the Magentospeed V3, gathered velocity readings for the actual temperature., Then I watched what my velocity did as the temperature of the ammo and rifle chambered increased until it stabilized at 2852-2854fps.
Now, I can add these variables to my Kestrel 5700X or Elite under Muzzle Velocity Temperature Variations and next time I shoot in the cold, comfortable, or hot temperatures have an increased confidence in my first shot being precisely and accurately on target each time.