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Like A Brick Wall By: Lyndon Combs

When loading a flat nose bullet pushing the bullet too fast may not be the best of ideas.  In this article I am going to touch on a little known fact concerning loading for certain bullets profiles.  You see when the bullet hits the air outside the barrel it is going to hit resistance from the atmosphere that the shooter is pulling the trigger. When using a flat nose bullet like with a .30-30, or other lever action rifles the blunt nose doesn't slice through the air like many pointed bullets, but actually due to the flat surface smacks into wind. It is not as catastrophic as actually hitting a brick wall where the bullet would more than likely be deformed, but it still can cause the flight path of the bullet to be affected, and in some cases cause the bullet to slow quicker further down range.  The harder it hits the air outside the barrel, or the faster it hits the air the more violent the flight will began. Another factor in this is the size of the meplat of the bullet nose because as with killing power the larger the meplat the more surface hits at one time. This is true with wind just as it is with an animal or any object.

You see the bullets flight starts in a violent way that causes the bullet to lose steam as it fights to overcome the resistance of the wind wall.  As with any disturbance in the path of flight it affects the trajectory of the bullet, velocity, and accuracy.  Just as with using fire formed cases that are fit to a specific rifles chamber anything that reduces the violent nature of bullet flight is important.

The next time you are out driving with your window down put your hand out into the wind, (please watch the road while you do this) and point you fingers into the wind. You should feel some resistance that would require you to push into the wind to hold your hand in place that will increase some as you speed the car up. This represents a pointed bullet hitting the air after leaving the bullet. Now hold your fingers to the sky your palm exposed to the wind. You will see now that as you increase your speed it causes your hand to move more violently requiring you to apply more pressure to hold your hand in place.  A bullet will fly better at a particular speed, and that is not always the highest velocity.  The easier a bullet leaves the case, fights its way through the barrel, and faces the  world outside the barrel the more accurate the shot down range.

The transitional period

Transitional ballistics is a complex field that involves a number of variables that are not fully understood; therefore, it is not an exact science[3]. When the bullet reaches the muzzle of the barrel, the escaping gases are still, in many cases, at hundreds of atmospheres of pressure. Once the bullet exits the barrel, breaking the seal, the gases are free to move past the bullet and expand in all directions. This expansion is what gives gunfire its explosive sound, and is often accompanied by a bright flash as the gases combine with the oxygen in the air and finish combusting.

The propellant gases continue to exert force on the bullet and firearm for a short while after the bullet leaves the barrel. One of the essential elements of accurizing a firearm is to make sure that this force does not disrupt the bullet from its path. The worst case is a muzzle that is cut at a non-square angle, so that one side of the bullet leaves the barrel early; this will cause the gas to escape in an asymmetric pattern, and will push the bullet away from that side, causing shots to form a "string", where the shots cluster along a line rather than forming a normal Gaussian pattern.

Most firearms have muzzle velocities in excess of the ambient speed of sound, and even in subsonic cartridges the escaping gases will exceed the speed of sound, forming a shock wave. This wave will quickly slow as the expanding gas cools, dropping the speed of sound within the expanding gas, but at close range this shockwave can be very damaging. The muzzle blast from a high powered cartridge can literally shred soft objects in its vicinity, as careless benchrest pistol shooters occasionally find out when the muzzle slips back onto their sandbag and the muzzle blast sends sand flying.

 

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