XyZspineZyX

10-10-2003, 02:52 PM

Gentlemen,

Pursuant to US M2 .50cal MG dispersion, the following data is taken from Department of the Air Force AF Manual 335-25: Fighter Gunnery, dated December 1950. It covers the following a/c - F47, F51, F80, F82, F84. I invite you to read the following and draw your own conclusions regarding accuracy and lethality of this weeapon in aerial gunnery.

The 100 pct dispersion value of the M2 .50cal was 8 mils in aerial gunnery application. In USAF parlance, an angular measure of one mil is equivalent one foot at 1000 feet.

At a range of 1000 feet (333 yards), 100 pct of the bullet strikes from a .50cal MG will therefore fall within a circular area 8 feet in diameter centered upon the point of aim. By the law of ballistic dispersion, if 100 pct of strikes fall within 8 mils, then 50 pct of bullet strikes will fall within a circular area of 2 mils (2 feet) diameter. 75 pct of bullet strikes will fall within a circular area of 4 mils (4 feet) diameter.

In the case where all guns of a fighter are point harmonized, then all the individual gun dispersion circles will be super-imposed upon one another at the point harmonization range. Assuming a 2 second burst of fire from eight x M2 50cal firing at 720 rpm each at a point harmonization range of 333 yards, 96 rounds of .50cal will strike within the two foot diameter circle of the 50 percent zone, i.e. - about 30 rounds per square foot within that circular area. To put this in perspective, it would equate to about 25 .50cal bullets coming at you through the glass screeen of your average 17-inch monitor. See below regarding the opinion ofthe USAF that this degree of fire concentration was overkill.

The USAF appears to have frowned upon point harmonization for the generality of their fighter pilots, who were not necessarily skilled marksmen. Here is what the manual says about harmonization -

QUOTE -

Although point harmonization results in a heavy concentration of bullets at a certain range, it produces excessive dispersion at others. The heavy concentration of bullets at a selected range is not always desirable, because the density of the concentration is in excess of that required. This is inefficient use of available fire power and requires too many refinements in aiming.

For a superior fixed gunner, point harmonization is probably the best type. For the average pilot, a pattern-type harmonization is more desirable because it compensates for minor sighting errors.

-snip-

Such a harmonization fixes the sight line approximately in the center of the projectile pattern throughout the effective range when the aircraft is flown at the basic harmonization speed. This relieves ths pilot of the need to calculate the projectile drop within the limits of effective range. The most effective range for harmonization purposes is considered to be 2,000 feet.

- UNQUOTE

To get a sense of the nature of a pattern harmonization, imagine six overlapping circular dispersion areas whose individual centers would form a regular hexagon when connected by straight lines.

Blutarski editorial comment -

This same gun, in 6 or 8 gun batteries, proved lethal at ranges up to 700 yards with the K14 gunsight. IMO, the M2 50cal was an accurate and powerful weapon.

Blutarski

Pursuant to US M2 .50cal MG dispersion, the following data is taken from Department of the Air Force AF Manual 335-25: Fighter Gunnery, dated December 1950. It covers the following a/c - F47, F51, F80, F82, F84. I invite you to read the following and draw your own conclusions regarding accuracy and lethality of this weeapon in aerial gunnery.

The 100 pct dispersion value of the M2 .50cal was 8 mils in aerial gunnery application. In USAF parlance, an angular measure of one mil is equivalent one foot at 1000 feet.

At a range of 1000 feet (333 yards), 100 pct of the bullet strikes from a .50cal MG will therefore fall within a circular area 8 feet in diameter centered upon the point of aim. By the law of ballistic dispersion, if 100 pct of strikes fall within 8 mils, then 50 pct of bullet strikes will fall within a circular area of 2 mils (2 feet) diameter. 75 pct of bullet strikes will fall within a circular area of 4 mils (4 feet) diameter.

In the case where all guns of a fighter are point harmonized, then all the individual gun dispersion circles will be super-imposed upon one another at the point harmonization range. Assuming a 2 second burst of fire from eight x M2 50cal firing at 720 rpm each at a point harmonization range of 333 yards, 96 rounds of .50cal will strike within the two foot diameter circle of the 50 percent zone, i.e. - about 30 rounds per square foot within that circular area. To put this in perspective, it would equate to about 25 .50cal bullets coming at you through the glass screeen of your average 17-inch monitor. See below regarding the opinion ofthe USAF that this degree of fire concentration was overkill.

The USAF appears to have frowned upon point harmonization for the generality of their fighter pilots, who were not necessarily skilled marksmen. Here is what the manual says about harmonization -

QUOTE -

Although point harmonization results in a heavy concentration of bullets at a certain range, it produces excessive dispersion at others. The heavy concentration of bullets at a selected range is not always desirable, because the density of the concentration is in excess of that required. This is inefficient use of available fire power and requires too many refinements in aiming.

For a superior fixed gunner, point harmonization is probably the best type. For the average pilot, a pattern-type harmonization is more desirable because it compensates for minor sighting errors.

-snip-

Such a harmonization fixes the sight line approximately in the center of the projectile pattern throughout the effective range when the aircraft is flown at the basic harmonization speed. This relieves ths pilot of the need to calculate the projectile drop within the limits of effective range. The most effective range for harmonization purposes is considered to be 2,000 feet.

- UNQUOTE

To get a sense of the nature of a pattern harmonization, imagine six overlapping circular dispersion areas whose individual centers would form a regular hexagon when connected by straight lines.

Blutarski editorial comment -

This same gun, in 6 or 8 gun batteries, proved lethal at ranges up to 700 yards with the K14 gunsight. IMO, the M2 50cal was an accurate and powerful weapon.

Blutarski