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09-08-2003, 03:16 PM

For those so interested, the following comes from AF Manual 335-25 FIGHTER GUNNERY, dated Dec 1950 -

QUOTE -

With an F-80 harmonized at 350mph IAS for a 1,000 foot range, the trajectory of the bullet will cross the sight line the first time at 1,000 feet. The trajectory will rise gradually to a height of 7 inches above the sight line and then will fall, recrossing the sight line again at 2,000 feet. (snip) With a cone of dispersion (the cone of bullet dispersion from a caliber .50 machine gun is about 4 mils for 75 percent of the rounds and 8 mils for 100 percent of the rounds) of 8 mils, or 16 feet at 2,000 feet, 6 guns (M2) firing 72 rounds per second give a bullet density of one bullet per 2.8 square feet per second, ...

- UNQUOTE

To put this in better perspective, the bullet density within the "75 percent zone" for 6 x M2 .50cal MG's at a convergence of 333 yards (about 300 meters) range will be about 1.1 rounds per square foot per second.

... and the bullet density for the "50 percent zone", which can will be roughly about 2 mils is about 2.8 bullets per square foot per second under the above-mentioned conditions. A 2 second burst would put 3 .50cal rounds into every square foot of an approximately circular target disk just shy of 13 square feet in area (4 foot diameter). For our European colleagues, this equates to 36 strikes per second within an area slightly larger than 1 square meter.

If convergence was set at 600 feet (200 yards) the effect on target would be about 1.67 times greater.

A P-47 with 8 x .50's would show 1.33 times better performance.

Also notice that, between 1,000 feet and 2,000 feet, the vertical separation between bullet path and line of sight does not exceed 7 inches. This remains ballistically true for some distance less than 1,000 feet and greater than 2,000 feet as well.

In terms of horizontal separation, assuming that wing guns are separated by an average of 15 feet on the airplane and are adjusted to converge at 1,000 feet, the bullet streams will be about 7.5 feet apart at 500 feet (167 yards) and 3.25 feet (1 meter) at 750 feet (250 yards).

Please note that all above discussions relate to the WW2 period M2 model of the .50cal. Pretty effective against a fighter target, I would say.

Blutarski

QUOTE -

With an F-80 harmonized at 350mph IAS for a 1,000 foot range, the trajectory of the bullet will cross the sight line the first time at 1,000 feet. The trajectory will rise gradually to a height of 7 inches above the sight line and then will fall, recrossing the sight line again at 2,000 feet. (snip) With a cone of dispersion (the cone of bullet dispersion from a caliber .50 machine gun is about 4 mils for 75 percent of the rounds and 8 mils for 100 percent of the rounds) of 8 mils, or 16 feet at 2,000 feet, 6 guns (M2) firing 72 rounds per second give a bullet density of one bullet per 2.8 square feet per second, ...

- UNQUOTE

To put this in better perspective, the bullet density within the "75 percent zone" for 6 x M2 .50cal MG's at a convergence of 333 yards (about 300 meters) range will be about 1.1 rounds per square foot per second.

... and the bullet density for the "50 percent zone", which can will be roughly about 2 mils is about 2.8 bullets per square foot per second under the above-mentioned conditions. A 2 second burst would put 3 .50cal rounds into every square foot of an approximately circular target disk just shy of 13 square feet in area (4 foot diameter). For our European colleagues, this equates to 36 strikes per second within an area slightly larger than 1 square meter.

If convergence was set at 600 feet (200 yards) the effect on target would be about 1.67 times greater.

A P-47 with 8 x .50's would show 1.33 times better performance.

Also notice that, between 1,000 feet and 2,000 feet, the vertical separation between bullet path and line of sight does not exceed 7 inches. This remains ballistically true for some distance less than 1,000 feet and greater than 2,000 feet as well.

In terms of horizontal separation, assuming that wing guns are separated by an average of 15 feet on the airplane and are adjusted to converge at 1,000 feet, the bullet streams will be about 7.5 feet apart at 500 feet (167 yards) and 3.25 feet (1 meter) at 750 feet (250 yards).

Please note that all above discussions relate to the WW2 period M2 model of the .50cal. Pretty effective against a fighter target, I would say.

Blutarski