Somewhat belatedly answering some questions

Reader Beach Bum Bill (not BillT and hereinafter B3) sent me a list of questions in response to this video I posted, showing a Canadian gun crew servicing their M777 in Afghanistan. B3 asks interesting questions – ones we take a few months to answer in detail in the various schools gunners attend to learn their trade. I decided if B3 is asking these questions, others of you might be wondering, too – so I decided to make it a weekend post.

I’ll intersperse the answers among B3’s

John,
I just looked at the Red Leg vid that you've posted and I've a bunch of questions as I know literally nothing about howitzers and big guns...  * How do you designate targets? Crosshairs, map coordinates, GPS ??? Which  generates another question: Are the trajectory calcs all done in a computer or do the  crews have to do it manually?

The answer to this series depends on several factors and varies from country to country, and era to era. How Lieutenant Donovan did it in 1980 varies from how Lieutenant Donovan would do it today.
When firing direct, the gunner lays the reticle of the direct fire telescope on the target.

When firing indirect, i.e., at targets the gun crew cannot see, the crew gets a series of commands. First is what type of shell, what type of fuze, and what charge (also known as zone). That tells them what they’re going to shoot and how much propellant they will use. Then they get a fuze setting (if appropriate) to set on the fuze; a deflection, which is the direction to aim the tube; and a quadrant elevation, which is how high to point the tube. There are other commands they will receive, which includes how many rounds to shoot, whether or not they will be adjusting or firing for effect, and whether they will shoot when ready or on command. This gives the crew the data they need to send the projectile on it’s way. That data will either come to them displayed on the Gun Display Unit (GDU), or via telephone, or even shouted out across the battery position. The GDU is the preferred method. This data is also recorded on a form at the gun by the gun chief.

That data comes from the Fire Direction Center, where 99% of the time it has been calculated by computer, though we do have manual means for computing that data. Whether done by computer or manually, the data takes the target location and the gun location, and calculates basic trajectory data based upon what are termed “standard conditions” for the projectile type, weight, type of trajectory desired or required (low angle or high angle) and environmental conditions of altitude, temperature, humidity, and wind direction and standard muzzle velocity.

Then you apply factors that account for all the differences (which are legion). The projectile data is modified by a correction factor if the weight deviates from the standard. The muzzle velocity is modified by continual measurement of actual muzzle velocity for the gun in question, and a factor applied to account for the variation which accounts for wear of the tube. The same is true for altitude differences between the gun and the target, the effects of weather, the effect of temperature on the propellant (colder than standard propellant doesn’t burn as fast – so you lose muzzle velocity), and for long range shooting they’ll account for the spin of the earth, and even crossing the equator or shooting in the polar regions. It all sounds complicated, and it is, but we’ve got pretty refined methods for simplifying the data and the processes. That process generates the data that ends up at the gun.

* Does the gun crew turn dials or push buttons to aim? I ask because as a kid I got to sit in/on a gun on the USS New Jersey and that gun had handwheels to aim it.

Towed guns use handwheels to traverse and elevate. Towed guns require the crew to actually lift the trails (the legs behind the gun) to make large shifts in deflection if they're going to do so quickly. Self-propelled guns use hydraulics with a manual backup, and use a joystick-like handle to control the movement of the turret and gun. The Gunner sets the quadrant elevation on his sight and then cranks the tube until his bubble is level. When firing multiple rounds, he keeps an eye on his bubble to ensure the tube isn’t moving, and levels as needed. The Assistant Gunner sets the deflection on his panoramic telescope and then sights through the pantel and moves the gun left or right until his aiming reference point (another class in and of itself) aligns in his sight. The tube is then pointed where the FDC has determined. How and when all this happens depends on the elevation of the tube – if you are firing multiple rounds at high angles, you might have to bring the gun back down to “loading elevation” so the crew can load the piece. You might not. 

Actually, that description above dates me and marks me as an old self-propelled artilleryman. In many, if not most, current towed gun systems, the elevation and deflection are set from a sight mount that combines both functions and are handled by one crewman.  Only the direct fire telescope is separate.  On guns like the Paladin, the gun is laid on target via computer, with the human crew there to spot-check and as a back-up.

* Is there a rule/reg that you have to have the target in sight? Meaning can you shoot over a hill where you cannot directly see the target?

The full answer to your question is really driven by the rules of engagement, the famous ROE. As far as the crew is concerned, for indirect fire, they never see the target. In fact, gun crews are pleased to never, ever, see the target in combat. Because that means the target can see you. The ROE usually requires that *someone* or *something* (a sensor of some type) or whoever is calling for the fires, have eyes on the target, for all the same reasons we do in direct fire engagements, so that you know what you are shooting at. In the “Big War” scenario, that may not be true, you may be shooting a series of pre-planned targets according to a schedule or plan, but in today’s environment, there are eyes of some sort on the target area. Just not the gun crew’s. There are always exceptions, but that’s the general rule.

* I imagine that you have to work with aircraft in the area so that they don't get hit by rounds going up or coming down and how does this impact joint ops? I'm thinking of a/c strafing afterwards.
 
We have a whole set of procedures set up to “deconflict” airspace – most often by not allowing indirect to be fired while aircraft are present and vice versa. We have a raft of graphical and time control measures designed to ensure that airplanes and projectiles don’t share the same space at the same time. It’s a little easier to do in today’s fighting vice the “big war” scenario, but everybody gets nervous and pays attention when airplanes are around, even unmanned ones. No point in shooting down your own UAVs.  Pilots, for some reason, do not ascribe to the Redleg credo of "Big Sky, Little Bullet."  Apparently, in the air, everything is magnified in size...

* In the vid, two of the crew carry a round up to the gun and turn away for a second pointing the nose of the round to another crew member before loading it. What are they doing?

The gun chief is personally responsible for every round that departs his position. The gun dogs are showing him the round and fuze so that he can personally verify that it is the correct round and correct fuze. Just as the powder monkey was holding up the zone charge so that the chief could verify that it was correct. He’s also going to verify the initial sight picture and that the bubbles are level on the sights – and keep an eye on them as a mission progresses.

* This last question is kind of stupid (please excuse) what is the proper term: Cannon, Gun or Howitzer? I know enough that my AR-15 is not a gun but a weapon.

A cannon is a generic term for anything bigger than a rifle, really. The tube of a mortar or the gun on a tank are properly referred to as cannons. In artillery parlance, a “gun” is a long-tubed, high velocity, flat trajectory weapon, whereas a “howitzer” is (generally) a shorter-tubed, lower velocity, arced-trajectory weapon. Guns were used to get long ranges, howitzers were used to get behind hills and walls and such – as well has they used to be cheaper. With the advent of the 50+ caliber tubes, we’re starting to blur the distinctions as we’re really building cannon that can do both jobs. Caliber is a term that can cause confusion, too. In small arms, caliber generally means bore diameter, as in .22 caliber or .50 caliber. In artillery, tube length is measured in calibers, meaning the length of the tube is expressed by dividing the length of the tube by it’s diameter. So the length of an artillery piece of 54 calibers is 54 times the bore diameter. In the case of a 155mm, that means a tube length of around 27 feet.