quick ballistic reference

[BU1(SCW)]

I found on Hornady's website their ballistics calculator and thought I would give it a shot and see how good it is. Actually, it was pretty close and beyond 300 yards could very easily be the trigger puller and not the calculator.Though, I still highly recommend that you try it at the range on paper before hunting with it. While the quick reference sheet was really handy, carrying the piece of paper to shoot prarie dogs and coyotes was really an effort in futility with wind, mud, and actually trying to shoot.
As I was putting away the luggage after a trip I remembered that my wife and I made our own luggage tags that are available at several big name shopping stores and that they were self adhesive and waterproof. I made one each for my .300 WinMag and my .204 and thought that maybe you guys would like a quick refernence sheet as well. If you dont like the Hornady site you could just as easily make your own on Excel and probably include more data. And, yes, for those worried about melting the plastic tag going around the .204's scope base, I will be replacing that with 550 cord as soon as I find where I put that.


Hope this helps some of you!

Dan

[Bunnybuster]

Dan the "inconsistency" at longer ranges could easily be the effect of temperature, humidity, and true barometric pressure.

The ballistic coefficient varies based on the air density. Air density varies by temperature, humidity, and barometric pressure. The ballistic coefficient given by the bullet manufacturers is derived by firing test rounds, while recording the temperature, barometric pressure, and humidity, and then adjusting the results for a standard temperature, pressure and humidity. If you are zeroed for a given distance, and know the muzzle velocity, temperature, humidity, and barometric pressure: Then you can calculate the BC for those conditions. It is then a matter of algebra to adjust from the BC under those conditions to a BC at standard conditions.

The BC is higher when the air is less dense: caused by such things as low humidity; lower barometric pressure; and higher temperatures. This results in less drop, and less wind drift.

The BC is lower when the air is denser: caused by high humidity; higher barometric pressure; and lower temperatures.

The Hornady manual has a pretty good discussion of the topic, and gives the equations. Don't know if it is on the website or not.

[OldTurtle]

The luggage tags are a great idea.

They would keep the info protected from the various elements, and can easily be changed to meet the change of ammunition being used...

Since I'm usually shooting up to four rifles and a couple of different loads each, it will be much easier to pull up the tag that goes with the ammo, rather than trying to keep notebook pages stable in a breeze...

[Rick in Oregon]

Dan, Bunnybuster is right, and to try to counteract the effects of BC changes due to the environmental conditions he outlined, I try to work up my loads in as close to the same conditions as possible, including altitude, which varies as much as 1,500' from my range to my favorite varmint patch. Although not perfect, it eliminates some of the variables we have to contend with when shooting at extended ranges.

Your luggage tag idea is a good one, although for me at least, the issue of the thing flapping about from the scope in the wind would drive me nuts, and I hate things taped to my rifle stock, which is why although about the same end result, I use the method shown below, which is also shared by some of our excellent Spec Ops guys in theatre at present. All 'come-ups' are expressed in MOA to correspond with the .25 MOA scope adjustments.



Easly to change for reuse, able to have thin plastic laminated over it if wanted, static, and is always easy to see when the caps are open. It's just another way to accomplish the same end. This type of thing is what these forums are really good for; sharing very cool ideas, and thanks for sharing yours.... I hadn't thought of that one.

[BU1(SCW)]

Bunnybuster,

You are absolutely correct! I am actually using Robert McCoys Launch and Flight dynamics of symmetric projectiles and the guys at Hornady turned me onto that book. It utilizes several methods including a breakdown on the Siacci method and is absolutely amazing. Its a little pricey, about the cost of a good Redding competition bullet seater, but well worth it to understand what is actually happening to the projectile once it leaves the tube. I am working my way through the differential equation calculus in the 6 degrees of freedom section And Rick hit the nail on the head, for now the Hornady site really is consistent enough until I have several shooting logs compiled to draw my data from to reduce variables and make a clean one shot kill.