Maybe i can help clarify part of this.
Part of my basic skill set as a artillery officer in the 1980s & 1990s was knowing how to calcuate the safety zones around the target area or impact area for all sorts of live fire training. We had a Safety Order that was litterally three cm thick with all the details for this. The zone width of margin varied according to the type of ammunition and the range. In general the higher weight the explosive charge and the longer the range the wider the safety margin. Even for 105mm ammo it was seldom the safety buffer width got down to 1000 meters. I can recall one instance where it was only 1200 meters. That nearly guaranteed a short round from a error of one propellant charge would still not land on the heads of anyone near the impact area. Outside that buffer there was little problem firing over the heads of anyone along the gun-target line.
With that in mind we often fired artillery at targets the manuver units would subsequently attack. Of course a 2000 or 3000 meter buffer would ensure a twenty or thirty minute walk for a rifle unit on foot, but we were usually practising air or mechanized assualt tactics, so the buffers were not extremely unrealisitc. For air strikes the safety zone was similar however the safety for dropping air ordinance was keyed on the Forward Air Controller eyeballing that the aircraft was pointed at the correct direction and attitude before releasing the bomb.
There were usually trenches, bunkers, silloutte targets, fake tanks or APC made up from piles of old tires and cardboard in the target area
That was how we did the manuver training with the explosive ordinance in the 1980s & 1990s. The decriptions of WWII veterans both told directly to me and from the books or magizine articals do not sound much different. maybe thery we a bit more particualr or sloppier about safety depending on the inclination of the commander.
I did occasionally run across old antiquated documents from the 1960s and earlier which decribed the procedures for training artillery observers much closer to the target or impact area. These involved building bunkers with X ammount of concrete Y ammount dirt berms Z aamount of angles slope, and using the tripod mounted periscope like binoculars. With that the safety margins were reduced to less than 500 meters. At the US Army Artillery School Ft Sill and some National Guard camps I ran across old abandoned bunkers built to the layout in the old training and safety documents. Also in a 1920s issue of the Field Artillery journal I found a artical describing training artillery observers with bunkers of this sort. Again I’ve run across WWII veterans describing using this same setup for training to adjust artillery fires at extremely close ranges.
So my best guess is the items decribed in New Zealand were similar to one or both of the methods we used. Did we have casualties in this training? Yes. Occasionally someone screwed up and one or more of us was maimed or killed. I cant recall every incident during my 20+ years of service but here area few that stuck in mind.
Circa 1980 Camp Lejune North Carolina. A propellant charge error (of multiple charges) caused a 105mm projectile to land far out of the impact area. It hit directly in front of a car on a public road, killing the driver and wounding her daughter (spouse and child of a Colonel). The gun section chief went to prison for manslaughter, the battery and battalion commanders were found negligent on numerous accounts, fined, relieved of command, and effectively had their career ended.
1985 Camp Pendelton California. While practising direct fire with 155mm howitzers the base plug from a exploded projectile struck a gun crewman in the chest. His flak jacket prevented penetration, but his ribs & breast bone had multiple fractures, and his internal chest cavity was sort of a mass of ruptured tissue.
1996 Ft Sill Okalhoma. A squadron of A10 aircraft were practising dropping laser guided bombs on the west target range. In midafternoon a A10 of the second flight of the day released, but the bomb did not remain locked on the laser dessignated target. Instead the 500 lb bomb went down at a extreme steep angle and hit the vehical used by US Army air control team doing the laser designation. Both team members were less than 50 meters from the vehical and both were dismembered by the overpressure of the explosions and fragments. Two US Marine artillery observation teams were on the same hill top between 100 & 200 meters from the impact. Fortunatly they only suffered hearing loss and mild concussions. Bizzarely we also had two Marines struck by lighting near that same hilltop a week earlier. Fortunatly they only suffered minor burns.
