Establishing a Firing Point

Establishing a firing point isn't just throwing down the base plate, pointing in a general direction, and letting it eat. 

Location, Location, Location. 

Whether it's direct or indirect fire the same principles apply. If you pick a bad piece of ground your baseplate jumps. If you misread your M2 compass your initial gun target line is off. If your stakes are off your optics are just expensive window dressing. Here is exactly how to select a position, find your azimuth of fire, and put out your aiming stakes the right way.

In military operations mortars usually try to set up in a defilade position because of tactical considerations. That's not always practical or safe in the civilian world. 

Do not just throw the baseplate down at the first open clearing you find. A mortar doesn't just push down when it fires. it shears back and down at an angle.

• Steer clear of loose sand, marshy topsoil, or ground choked with heavy root systems. Roots act like springboards under heavy recoil, kicking the baseplate after every shot.
• Look for firm loam or clay. If you are stuck with dry, rocky soil, you will need to clear the loose surface rocks down to the solid sub-layer so your baseplate spades can actually bite.
• Clear away all loose organic matter, soft topsoil, and root networks down to the hard sub-surface loam, clay, or hardpack. 
• Look up. A high-angle system needs a clear sky. A single overhanging tree branch 30 feet up won't just deflect your round, it can send it off in any direction, including back at you. 
• Look out. Even though a mortar is a high angle system you still need a clear line of sight and room to set out aiming stakes. 
• The rule of thirds. When selecting a firing point use the rule of thirds. Take your maximum range and divide it into thirds. One third of your range should be between the gun and the target and two thirds should extend behind the target.  

Orienting the Gun Target Line with the M2 Compass

The M2 compass is an exceptionally precise instrument graduated in mils (0 to 6400) rather than degrees, allowing for highly granular angular measurements (1 mil ≈ 1 meter of lateral drift at 1000 meters). However, its magnetic needle is highly susceptible to local ferrous interference.

• To prevent a corrupted reading (known as magnetic deviation), the operator must step away from all metallic and electrical structures. You must maintain these minimum clearance distances:
  • High-voltage power lines: 100 meters
  • Vehicles, artillery pieces, or generators: 10 meters
  • Mortar tubes, equipment, and radios: 5 meters

Before taking a reading, ensure your compass's local magnetic declination constant is manually dialed into the index scale. This ensures your magnetic readings align perfectly with your grid map data.

• Stand a minimum of 10 meters directly behind the designated weapon hub, facing your primary direction of fire. Raise the compass cover to a 45-degree angle. Flip the rear sight up. Center the circular level bubble. Look through the rear sight groove, align the cover mirror centerline with your target azimuth, and project that visual line forward and set out an aiming stake or select a distant, immovable terrain feature. This is your Gun Target Line.

Dialing It In

Your aiming stakes do not just give the gunner something to look at. they form an optical reference system designed to flag and measure weapon migration during firing.

The Assistant Gunner (AG) takes two stakes and walks out on the established azimuth line. The Gunner stands at the weapon position, looking through the sight unit (or tracking with the M2 compass). The Gunner hand-signals the AG left or right until the Far Stake is driven in at exactly 100 meters.

The AG walks back to exactly 50 meters. Looking through the crosshairs, the Gunner directs the AG to plant the Near Stake so that it perfectly aligns with the Far Stake.

As rounds are fired, the gun will inevitably shift. When the gun migrates the near and far stakes will appear to separate in the gunner’s sight.

If the stakes drift apart, do not simply crank the traversing handle to align on one stake. This introduces a catastrophic angular error. The gunner must utilize the sight's internal micrometer dials to measure the gap between the stakes, compute the displacement value, and physically reset the bipod legs to re-align the entire weapon system back to the original Gun Target Line.

The Takeaway

Precision gunnery is won or lost in the mils. If your position selection is lazy your baseplate will move. If your compass work ignores ferrous interference your Gun Target Line is off. Take the time to clear your firing point, anchor your platform, lock in your stakes, and let the mechanical system handle the rest.