Common rifle barrel lengths for 243 Winchester rifles, are; 20, 22", 24" and 26", all of which will show a variance in the ballistics of the 243 Winchester.
Variables such as riflescope choices, riflescope mounts and properly mounting your riflescope affect the line of sight above the bore centerline, which contribute to ballistic variances as well.
To achieve maximum accuracy from your 243 Winchester rifle for proper ballistic evaluation you need to, break-in your rifle barrel and then accurately sight-in your rifle.
External ballistics pertains to bullet velocity, energy and trajectory down-range. Bullet trajectory is the flight path of the bullet relative to some known and fixed points.
Bullet Trajectory And Sighting Plane:
1. Point blank range when sighting in a rifle is the first point at which the line of sight intersects with the bullets path in the bullets trajectory.
2. Mid-range rise when sighting in a rifle is the highest point in the bullets trajectory between the point blank range and true zero.
3. True zero when sighting in a rifle is the second point at which the line of sight intersects with the bullets path in the bullets trajectory.
4. Maximum point blank range when sighting in a rifle is the height of the mid-range rise and the bullet drop beyond true zero, both are equal in measure.
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Rifle Sight Height And Bullet Trajectory:
To properly sight-in a hunting rifle a person needs to know a little bit about their scope mount height of their rifle as this affects the sight plane that intersects with the bullet's trajectory.
Rifle Sight Height to Bore Center Line:
Open Sights = 1 inch sight height.
Rifle Scope Center Line to Bore Center Line:
Low Scope Mount And Rings = 1.5 inch sight height.
Medium Scope Mount And Rings = 1.8 inch sight height.
High Scope Mount And Rings = 2.0 inch sight height.
Rifle Barrel Length, Bullet Velocity And Energy:
Bullet velocity readings are generally taken from a rifle barrel length of 24 inches and using the following formula the bullets energy is determined; velocity x velocity x bullet weight = _ divided by 450,340 = bullet kinetic energy in foot pounds.
If your rifle barrel length is not 24 inches then you have to recalculate the bullet velocity and bullet energy.
Rifle Barrel Length Shorter Than 24 Inch You Subtract Velocity.
Rifle Barrel Length Longer Than 24 Inch You Add Velocity.
2,500 to 3,000 feet per second advertised velocity, adjust at 20 feet per second per inch from standard of 24 inch rifle barrel.
3,000 to 3,500 feet per second advertised velocity, adjust at 30 feet per second per inch from standard of 24 inch rifle barrel.
3,500 to 4,000 feet per second advertised velocity, adjust at 40 feet per second per inch from standard of 24 inch rifle barrel.
Bullet Ballistic Coefficient:
The bullet ballistic coefficient, higher B.C.s mean flatter trajectories and higher retained energy down-range on target. A ballistic coefficient is the measure of a bullet's relative ability to overcome air resistance. Each bullet is assigned a numerical value expressing this efficiency. Ballistic coefficient calculations combine both shape and sectional density factors.
Bullet Sectional Density:
Bullet sectional density is a mathematical factor expressing the relationship between the weight of the bullet and its cross-sectional area. Sectional density best describes a bulletís length as to its diameter, the higher the number, the longer the bullet. Generally speaking, longer bulletís of a given diameter (high S.D.) will penetrate deeper than will shorter bulletís of the same given diamter (low S.D.). Having said that, bullet construction ultimately determines its usage for hunting, always follow recommendations by the manufacturer.
Before the bullet is down-range and on target, you have to know whether the bullet will have enough energy retention to cleanly harvest the animal. A bullet's kinetic energy is measured in foot pounds, and this is a proxy for what's generally termed stopping-power. The higher a bullet's energy at the point of impact, the greater its stopping-power.
Target Size And Bullet Energy Needs:
Just as important is the size of target that a game animal that your hunting presents to you, typically standing broadside, exposing heart and lung area. Below are several hunting ballistics sight-in charts for 243 Winchester ammunition that categorize this ammunition to its practical use on various game animals for hunting.