1951: Glossary

Angle of sight

The angle between the line of sight and the horizontal plane. The angle is said to be plus when the target is above the horizontal plane and minus when the target is below it.

Crest clearance angle

The angle by which the barrel must be raised above the line of sight to the crest to ensure that all the bullets will clear the crest.


A lateral displacement of the lines of any, or all, guns.

Direct fire

When the gun is laid directly on the target by means of the backsight and foresight.

Fixed line

A term denoting that measures have been taken for maintaining elevation and direction in darkness, etc, to ensure that fire will fall on the pre-arranged target area.

Flanking fire

Fire applied across the front of a locality occupied by own troops, or, if they are advancing, at an angle to their line of advance.

Ground angle

The angle between the line of sight to the target and the line of sight to own troops when using overhead fire.

Group commander

An officer or NCO commanding two or more machine gun sections.

Indirect fire

When a gun is laid to hit a target by other means than by laying on it direct.

Line of fire

The direction of the target from the gun.

Minimum clearance

A term used to denote the minimum height of the centre bullet of the cone above the heads of our own troops for the latter to be safe.

Near limit of arc

The nearest line across the arc of fire on which fire may be required.

Overhead fire

Fire passing over the heads of our own troops.

Pivot gun

The gun used as a basis for a calculation.

Quadrant angle

The angle which the axis of the barrel makes with the horizontal plane.

Quadrant elevation

The quadrant angle expressed in terms of a range and an angle of sight.


The recording of the direction and elevation necessary to hit any given target found by ranging.

Safety angle for flanking fire

The minimum lateral angle by which fire must clear our own troops for them to be safe.

Safety angle for overhead fire

The minimum angle which must be included between the axis of the barrel and the line of sight to own troops to ensure their safety under overhead fire.

Tangent angle

The angle which the axis of the barrel makes with the line of sight.

Zero line

A line of reference on which all guns are parallel and from which switches are measured.


DP Drill pattern.
IA Immediate action.
MMG Medium machine gun.
MPI Mean point of impact.
OP Observation post.
RAP Regimental aid post.
RV Rendezvous.
QE Quadrant elevation.


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