vital zone radius

[shaunharkin]

looking for a answer what is it all about I zero my rifle at a 100 meters My sight height 2.1in
can anyone help me our explain to me

 

[Forum Boss]

The Vital Zone Radius (VZR) as used by JBM Ballistics program is defined as follows:

Vital Zone Radius
Radius of the vital zone for which the maximum point blank range is calculated. The vital zone is defined as the area from one radius below the line of sight to one radius above the line of sight.

Not sure how helpful that is, because it still requires more specification to be meaningful with a specific load/target.

 

[necchi]

For the purpose of explanation, a "Vital zone" refers to the heart/lung area of a game animal,
(there are other vulnerable areas but lets just use one)

So a Vital Zone Radius would be a circle that includes all or most of that heart/lung and some area near where if struck by a bullet would insure a quick and certain kill with the shot.

A Squirrel, Rabbit, or Ground hog would have a small area of vital zone radius as compared to a large animal like Deer, Moose or Elk, say 2-4" instead of 10-12"`s (follow so far?)

Now, when you use a ballistic program that asks for a VZR in the calculator you simply choose a size circle you feel your intended game will have.
(let's say you choose a 10" circle)
This data is many times used to determine a "Point Blank Hold" for your bullets travel, it's usually defined as a given distance,, like 214yrds,,,
Tha means your bullet's arc will be inside that 10" circle from the muzzle all the way out too 214yrds and you will not have to "hold over" with the scopes cross hairs unless your target is further than that 214 yrds,,,
Get it?

I load for a friends 223 WSSM, we've got a 55grn bullet screaming at 3860fps, the number cruncher program say's he has a 4" point blank hold out too 390 yards!!

 

[sscoyote]

Whatever you do be sure to calculate it for no more than 3/4ths anticipated VZR, due to the idealistic nature of ballistic programs. Always important to have some "wiggle room" for guns that don't shoot into the same hole at all ranges from all positions.

 

[wapiti25]

I would not use a point blank dia bigger than 10" for big game such as a elk, Mule deer less . That is 5" above or below your hold, smaller animals would have to be less for me. Maybe 6" for antelope and hogs maybe 5", You need to look at the anatomy of the animal you are going to hunt. The bull elk on my wall measures about 32" back to brisket. This is a very large bull 7X7 with a 354 Boone and Crockett score. A large mule deer I have is 18", I used to hear that the back to brisket was an average of 16" for big mule deer bucks. I have a "cheat sheet" taped on the side of my stock with the drop from my Zero, usually 200 yds. You can use inches down or MOA/clicks up for a dial up scope at each range on a "cheat sheet" if your turret's are not marked for range. I had the opportunity to see/use one of the G7 range finders on a trip to Wyoming in Sept., we used it on antelope and it is the best I have ever seen. I have not had the opportunity to use many of the high end range finders, I have the Leupold RX IV 1600 yd rated that has trouble beyond 400 yds on antelope. I wish I could afford the G7.

 

[K22]

Would like to add a few additional points regarding the concept of "point blank range" concept.

It's a useful concept for hunting when applied to the vital area of the animal you intend to hunt. While ballistic programs / calculations may get you close actual, your data should be verified by testing on the range at the distances you anticipate shooting.

In addition, as mentioned by a previous poster, you need to take into account the rifle's / load's accuracy capability (group spread) and the shooter's ability when shooting under field conditions. The affect of these two parameters will have the practical affect of expanding the zone beyond the vital zone of radius.

An effective way to determine the capability of the entire system, (Rifle, Load, Shooter) is to practice under field conditions to determine the vital zone radius you can hit. Use a target containiing concentric circles and measure your performance.

I use sheet of typing paper with 3", 4", 5", and 6" concentric circles with a 1 1/2 inch center orange dot. I shoot five shot strings at various distances, 100 - 200 - 300 yards off of shooting sticks (my preferred field hunting method). This gives me a good idea of my system's capabilities for varmints and big game. If I can connect 4 out of 5 shots on the circle I've chosen to represent the vital zone for the animal that I intend to hunt then I considered I have a reasonable chance of making the shot. e.g. 3" varmints, 6" big game.

Besides, it's a lot of fun if you enjoy shooting and testing yourself.