Danger Space is one of those terms that’s been around shooting for many years but rarely seems to come up these days in defining how effective a particular load combination is. This may in part be as a result of the increase in the use of laser range finders which can pin-point the exact range to a given target for Danger Space is particularly important to the shooter aiming at an unknown or uncertain distance such as the military sniper or hunter.
To many, Danger Space is the ultimate measure of merit for a trajectory where that measure is the likelihood of hitting the target that one is aiming at.
So what is Danger Space and why is it important? In short, Danger Space is the distance over which, a given target of known height, is in danger of being hit by the trajectory of the bullet.
In the diagram above the dashed lines represent a target of known height, say 10 inches. The highlighted arrows show where the trajectory of the bullet first crosses into that 10 inch zone (after initial firing) and then also where the trajectory takes the bullet out of the 10 inch zone. It can be seen from the plot that the bullet enters the zone at say 580 yards and leaves it at 620 yards. This means that a 10 inch target would be in the Danger Space of this trajectory for 40 yards (580 to 620). Naturally the longer the Danger Space the higher the likelihood of hitting the target and this is where Danger Space starts to become critical for the shooter shooting at unknown or at least uncertain distance targets.
Let’s take the example of a military sniper. The option to laser range find is not an option. Passive surveillance, a non-reflective target, there may be any number of reasons as to why the laser range finder is out of play. So the sniper goes back to basics and starts to range the target using one of the options open to him such as using the mil-dots on his scope or bracketing or whatever it may be. What the above graph means is that with that round the sniper could be 40 yards out with his range estimation and still record a hit on that 10 inch target. This is why Danger Space is crucial to the unknown/uncertain distance shooter but of less impact to the target shooter who is invariably shooting at a known distance target. Having that latitude or leeway in calculating the range could be the difference between a hit and a miss.
So once we start to consider Danger Space and the impact, quite literally, it can have on our ability to hit a target the trajectory of the bullet and therefore the bullet’s Ballistic Coefficient (BC) start to take on a much greater significance.
A bullet with a high BC will tend to have a flatter trajectory out to a given distance than will a bullet with a low BC out to the same point, thus increasing the Danger Space. At that distance therefore, the Danger Space for the high BC bullet might be 40 yards but the Danger Space for the low BC bullet might be only 20 yards due to its much steeper angle of attack. In short, the shooter has to be much more accurate with his ranging to ensure a hit with the low BC bullet than he does with the high BC bullet.
In recent years we have seen the introduction of Very Low Drag (VLD) bullet designs with extremely high BC’s that have given some of the more traditional rounds such as 50 BMG a new lease of life when it comes to a longer, flatter trajectory. Many of these VLD bullets have extended the effective range of these calibres by increasing the Danger Space at longer ranges.
Where Danger Space becomes interesting is to understand how it changes over the course of the trajectory. A fast flat light round at 300 yards maybe dropping like a stone at 600 yards whereas a slow heavy round, with a higher BC, may have a relatively worse Danger Space at 300 yards but a relatively better one at 600 yards. In his book Applied Ballistics for Long-Range Shooting; Bryan Litz illustrates this by comparing the 220 Swift round to the 243 Winchester. At 700 yards the .243 Winchester has a Danger Space of 37 yards compared to 27 for the 220 Swift. A 37% difference in favour of the heavier, slower round.
So what does all this mean? Well, if you only shoot at known distance targets, not much to be honest, but if your shooting entails engaging targets that are at unknown or uncertain distances, then knowing the Danger Space of the trajectory of the round you’re shooting could make all the difference.
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Figure 14 Ltd is a partner of THOR Global Defense Group and Knesek Guns importing large calibre precision weapons from THOR and EDM into the UK.