PRONE SHOOTING POSITION
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The information below is an extensive analysis of how to achieve the best set up and shooting position. It's taken from an ISSF guide - and although it's quite lengthy if you're serious about your shooting it'll repay your time in reading through it.
Biomechanical analysis
The prone position is the most stable shooting position. The reason is the largest support area of the body while the center of gravity is at the lowest height. This gives the best stability to a system shooter-rifle.
From the biomechanical aspect, the most important area of interest is the combination of shoulder, arms and head positioning. The highest stability of a position is achieved when the COG of the rifle is as close to the centre of this zone as possible. Therefore, the shooter’s body should be rotated no more than 20 degrees in relation to the shooting line. Higher rotations cause the COG of the rifle to move to the right and instabilities in the shooting position.
Straight forward App. 20 degree body angle Bigger body angle
The forces going straight back-forth should be equal, as should the ones going up-down. This means that the left-hand pressure on the rifle should be equal to the pressure of the stock in the shoulder. Based on that, the length of the stock and the sling is determined, as well as the balancing of the rifle.
In the sagittal plane, the pressure of the head on the cheek piece should be equal to the pressure of the right arm and hand. This acts as a parameter to determine the position of the right elbow.
The angles of the left forearm and upper arm should be the same according to the supporting area. In that case the force is going straight back.
The basic prone position consists of the following elements (right-handed shooters):
Upper body and legs
Body of the shooter should be slanting so that the vertical axis of the shooter and the shooting line is forming an angle of 0-20 degrees. The spine is straight. The spine and shoulders are approximately T–shaped. The left shoulder is drawn forward to slightly open the alignment of the shoulders. The right shoulder should be relaxed.
Slanting in this position is more comfortable for the shooter as the rib cage is not tight and provides freer breathing. It also provides the shooter with ideal conditions for leaning of the head onto the cheek-piece, and positioning of the butt plate onto the shoulder. With these adjustments, the shooter should have more correct aiming.
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Legs should be spread without any tension; the left leg should be leaned onto the ground with the tip of the toes. It is more beneficial to shoot in the shooting shoes because they provide the stability of the left leg with their flat front. The left leg is exactly in line with the rest of the body and is parallel to the spine. The right leg should be bent at the knee (about 45 degrees) and the right foot should completely lie on the ground with its inner side. Bending of the right leg makes breathing easier and avoids pulsation in the stomach as the shooters weight is primarily on their left hip.
Arms
Left arm is bent at the elbow and placed as far forward as possible to the hand stop, but to the limits prescribed by the regulations (the smallest angle between the forearm and the ground is 30 degrees).
Left elbow is placed slightly to the left of the rifle.If the elbow is placed directly under (or further to the right) the rifle, it will typically result in muscle pain in the shoulder area. When too much pressure is given to the left side of the body, balance is also affected. In order to maintain this position, the elbow has to stay exactly in the same place throughout the whole shooting session or a competition. Left arm has to be as relaxed as possible.
The wrist of the left arm is straight, with a straight line going from the shoulder to the upper arm. This straight line continues through the forearm to the supporting hand. The left wrist should have minimal bending and should be relaxed.
The fingers on the left hand should not be tight around the stock. The rifle is leaned onto the middle of the hand, a little toward the thumb.
Majority of the rifles weight is placed upon the left arm.
The placement of the right arm is very important in prone.
The right hand holds the pistol grip with a moderate grip. The wrist of the right hand should be straight while the base of the trigger-finger should be separated from the pistol grip. This provides the best feeling for triggering - the shooter should feel as though they are hugging the rifle with his right hand.
The right elbow should be neither pushed near the body, nor separated with effort aside. Once the pistol grip is taken, the elbow is freely put to the ground. The elbow must always be lowered to the same place in order to maintain alignment of the position.
Butt Plate and Length of the Stock

The butt plate is placed on the inside of the shoulder as close to the head as possible.

The length of the stock should be determined so as to allow good contact in the shoulder. The pressure in the shoulder should almost be the same as the pressure of the rifle to the left hand. If this pressure is weak, the stock should be extended - if the rifle pushes the shoulder backward, the stock should be shortened.
The hook should be between the back and the arm, and should not exert pressure on either side.
The hook should be between the back and the arm, and should not exert pressure on either side.
Head
The head is in front of the spine and leans on the front of the cheek-piece of the stock. The head must not be turned to the right or angled down as it will cause the shooter to aim astray or aim under the forehead (eyebrow). The head should be relaxed. The belt on the right part of the jacket should be tightened to avoid pressure on the neck.
Sling
The sling should firmly connect the left arm and the hand stop on the fore-end stock. The sling should form the firm triangle composed of the left forearm, left upper arm and the sling. This triangle should act as the artificial support for the rifle, which will release the muscles of the left arm while holding the rifle. The sling must not be loose or too tight. If it is loose, the stability decreases and the muscles of the left arm are included into holding the rifle. If it is over-tight, the weapon shakes and there is a pulsation due to the poor blood circulation.
The sling can be put on the upper arm at two places - at the lower part, near the elbow - at the lower position and high, near the shoulder - at the high position. The sling must not be positioned at the middle of the upper arm because then it directly lies in the middle of the triceps and causes the interruption of blood circulation. The sling should be placed as horizontal as possible.
Position Height
The prone position, concerning the position of the left forearm, can be high, low or medium - all three positions are correct. The only condition is that when using the low position, the angle between the forearm and the ground must be larger than 30 degrees.
Each of these three positions has its own advantages and disadvantages and the height of the position depends on the shooter's body proportions.
The low position is the most stable for shooting as the bodies center of gravity is the lowest. It is a less convenient position as it; presses the rib cage, affects breathing, creates pulsation disturbance, makes it difficult to keep the head correctly positioned, causes tension of the neck muscles. These all add up to the consequence of poorer visibility of the sights, because aiming takes place under the forehead (eyebrow). Because of the inconvenient shooting conditions in this position, but with the greatest stability, the shooter who uses this position should have a fast rhythm of shooting.
The high position relaxes the rib cage, makes keeping the head correctly positioned easier. This position is very good for aiming but it causes a disadvantage as the center of gravity of the system shooter-rifle is high. With this higher center of gravity, the stability of the rifle and shooter are considerably smaller, and the pressure placed on the left elbow is much stronger than other positions. This high center of gravity also causes the muscles to tighten, which causes the shooter to become fatigued more quickly than in other positions.
The medium position is most frequent with the shooters because it avoids bad and keeps good sides both of the low and high position.
The position modifications depending on the body constitution
Tall shooters
Tall shooters should adjust the position to a longer arm length. They typically assume the higher position, as it provides the most benefits to taller shooters. The sling is in the high position on the upper arm. The left elbow is more to the left, while the right elbow is closer to the body and the right shoulder is higher. As the hand stop is moved forward in this position, the balance of the rifle is shifted backwards, so it is advisable to use the weights on the front of the stock to move the balance of the rifle closer to the left hand.
Short shooters
Because of their shorter arms, short shooters should take a lower position. Position of the sling on the upper arm is set up on the lower position. The left elbow is placed closer to the rifle, while the right elbow is positioned away from the body and the right shoulder is lower in order for the shooter to reach the required target alignment.
Plump shooters and female shooters with big breasts
Shooters with this body type typically take a higher position. The right leg is bent more and they lean on the left hip, as it makes breathing easier and avoids putting the pressure and pulsation on – and pulsation in - the stomach.