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Range Report Danger space vs Hit Threshold

Timo Turl

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Full Member
Minuteman
May 24, 2010
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What is a Hit Threshold and how does it differ to a Danger Space ? I'm confused about how you employee these two and if they relate at all to one and other. Thx
 
Re: Danger space vs Hit Threshold

Danger space is a way to express how precise the range need to be for a shot to be usable. For a given target size, Danger Space is the range where the bullet path is no higher than the top edge of the target to the range where it is no lower than the bottom edge.

For example, given a .308 175gr Match, nominal DS for a 1000 yard target 12" in diameter is 995 to 1009, -5/+9 yards. For a 500 yard target, 465 to 530, -35/+30.

I presume Hit Threshold is actually Hit Probability, which is rather complex to determine. You need a good value for the CEP (circular error probable), which is YOUR NOMINAL GROUP SIZE at that range. This includes all the "flyers", it's not jut the best groups you ever shot. It includes the DS problem and your ranging precision for the range, plus your wind call precision and the drift +/- for that precision value. Now you can plot your true nominal shot placement and determine hit percentage by the area of the target compared to the area of the group. If you do it correctly, you'll have a pretty good idea of the percentage chance you'll hit a given target at a given range on the first shot. Most people would find that number to be shockingly low at any appreciable range for a realistic target if there is much more than 5 mph of wind involved.

Just as an example, the REAL Hit Probability of an 800m 1 MOA target with a .308 in 10mph winds is around 5-10%. Most will deny that, and think they do MUCH better.
 
Re: Danger space vs Hit Threshold

What you are calling danger space was taught years ago but dealt more with machine guns then rifles, althought during the trench fighting of WWI it was also taught to rifleman.

I use to run Machine Gun schools for the NG where we used the M-60 as a medium machine gun instead of an light machine gun.

Basicly you compute the angle of departure/angle of fall to get your rounds over the manover troops you are supporting. Back then the heavyand medium machine guns were pretty much static.

The best text on the subject is "MACHINE GUNS" 1915 by (then) Major J. Hatcher, Major G. Wilhelm, and Major H. Maloney.

There is a lot of math involved.

An Example: The range to the target is 1750 and the treme limit to which the troops may safely advance.

Angle of departure 1750 yards = 42.5 mils
Angle of safety = 21.o mils

Range whose angle of departure = 21.5 mils is 1250 yards. Therefore, 1250 yards is the nearest approach that may be made to the target under the circumstances.

This can be done also with the rifle but it would be easier if you had something along the lines of the 1905 sights (ladder sights) they had on the 1903 Sprngfield.

It can be done, but not practical in the the real world of the rifleman, by the time you got it all figured out, everything changes. It's not like the days of trench warfare.

If you feel its needed, then go talk you you're Red Leg people, they can figure it out on their fancy computer fairly quickly, and all you have to do is add it to your range card.
 
Re: Danger space vs Hit Threshold

The reason i ask is Loadbase just came out with a free upgrade with below sent in the mail. I was trying to figure out what it all means :)

New “HIT THRESHOLD” feature

The Hit Threshold solution is quite different than Danger Space, since it does not account for the Max Ordinate (for both the ascending and descending branches) thus the Zero Range is of no consequence, and:


ü Its calculation is not limited by any Slope angle (thus not limited to level fire).


ü For a given Target Distance, the Hit Threshold is expressed as “value pairs”, indicating the Minimum and Maximum range for a hit, given a center-mass POA. RED VALUES (null) indicate NO value for a given Target Distance, also called Dead Space


ü Since for the calculation of the Hit Threshold, the Zero Range is of no significance, to yield a solution is always possible. Therefore it’s a more suitable solution for indirect fire on low height targets, as opposed to the Danger Space, which is especially practical for tall targets, on typical HTI scenarios.


ü The proprietary algorithm implemented in this program yields the EXACT value and is not an approximation.


ü The Target Size (vertical dimension) must be equal or greater than 10 inches (or equivalent units)



ü The Hit Threshold is a concept, which finds its roots in the Hitting Space, as defined in Artillery.


NOTE : Unfortunately is very common to see some authors using the term DANGER SPACE in a completely wrong way. As a concept derived from Naval Artillery, it has a very narrow and well defined meaning, which is rightly implemented in LoadBase 3.0© and ColdBore 1.0©, so beware of some programs “featuring” Danger Space, when they are not even close.
 
Re: Danger space vs Hit Threshold

Ok, I confess not understanding the above text. I've got no idea how zero range is not considered. If I zero at 100 yards and hold center of a 500 yard target I can pretty tell you the "Hit Threshold" is zero, whereas if I zero at 500 I'm getting a hit.

As far as indirect fire on low targets with small arms, who's even considered that since WWI? Even if it produced a usable solution, what user of the program would implement it?

I guess I'd have to see some results to get an idea of what's being proposed here, as I don't grasp the signifigance from the given explanation.
 
Re: Danger space vs Hit Threshold

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">As far as indirect fire on low targets with small arms, who's even considered that since WWI? Even if it produced a usable solution, what user of the program would implement it?</div></div>

It is a valuable tool or tactic. I taught it in my Machine Gun Schools, (and sniper schools to a point).

Let's say you have friendly troops in a small valley, your guns are on one side, and the indians are on the other. Now we know you don't set up on a crest of a ridge, but you use the "military crest" or just down from the top.

Ok you recon plt spots the indians staging on the far ridge, the far military crest. You don't have access to arty or mortors.

You can engage the indians with indirect "small arms fire", machine guns and rifles.

We're not talking pin point accuracy but grasing or searching fire. This disrupts the indians protecting the friendly's in the valley.

It's not really that hard to figure out. You have to know your angle of departure and angle of fall. Just takes a bit of math to be able to engage the bandits yet not put your friendlies in danger.

 
Re: Danger space vs Hit Threshold

Sounds to me like they are referring to a new twist on what has always been called Point Blank, but shedding the word maximum, as a zero distance is not now part of the equation.

Every target has a error factor, that even a hit at the max error factor, will still damage or kill the target.
 
Re: Danger space vs Hit Threshold

Maybe I misunderstood the OPs ideal of "danger space".

I didn't look at Point Blank Zero, I was thinking of overhead fire, such as shooting over friendlies.

Lets say you are covering advancing troops and to do that you fire over their heads.

As we know the bullet path is an arc. It goes up and comes down.

That means there are two points where the troops are in the "danger space", where the bullet is climbing and where the bullet is falling. Between those two points is a safe zone.

What you need to do is calculate the Maximum Ordinate. To do that you need to know the time of flight for the bullet to reach a certain distance.

Sight graduations are calculated that the drop of the bullet during the time of flight will be compesated by the height to which it rose above the target by having the line of departure directed upwards.

The law of falling bodies tells us the distance in feet through which a body falls from rest in a given instant of time equal 16 times the square of time in seconds.

Knowing the time of flight we can compute the two points in the arc where the troops will be safe from overhead firing and the point where firing can commence and stop whereby not putting the troops in danger.
 
Re: Danger space vs Hit Threshold

Kraig, I do understand all the MG stuff, I've got a slide rule and firing tables along with the clinometer for my Vickers. Excepting military free fire areas, it's not really a good idea to be lobbing rounds at something you can't see. Even then, without an FO can you really say you are having an effect?

I can see this being used by G's that have neither arty, air or explosives for a MA, where you could register a gun onto a crossing point and fire on a signal.

None of this seems to answer what the heck is meant by the description of "Hit Threshold". Gunfighter seems to be onto something, but the "value pairs" is still an issue, and you still need to set a particular zero to actually get PBZ, and I don't see the description stating that as part of the solution. I'd expect to enter target size and be given back a zero setting and the max range.
 
Re: Danger space vs Hit Threshold

Target-Danger space, was also a goal that was not truly achieved with the M-198 Duplex ammo, when shot at max range. With a 60 on the ground it was so/so, but a mounted or free gun(60)on a bird it worked very well. The dispersion of the second projectile, (do to air speed I believe), made it a better round than issue ball. It had to be hand linked, but was more than worth the effort.
 
Re: Danger space vs Hit Threshold

I don't know if this is any help, but "hitting space" as it was (is?) used comes from naval artillery. If I have it right, it was often but not always the same as danger space, and could be used to calculate the probability of a hit, which helped determine the size of a salvo.

NAVAL ORDNANCE AND GUNNERY VOLUME 2, FIRE CONTROL See <span style="font-style: italic">18A2. Definitions</span> through <span style="font-style: italic">18A9. Spotting MPI to center of hitting space</span>

From UNITED STATES NAVY EXTERIOR BALLISTICS 1935, 17B11. Danger space and hitting space and also the entire Appendix B - hitting space formulae and how to construct hitting space tables.
 
Re: Danger space vs Hit Threshold

Many years ago talking to both a F4 and A-1 Sky-Raider, Jocks. They both made comment to the Circular Error of Probability and how it changed back an forth between X flight level an/at X speed.
 
Re: Danger space vs Hit Threshold

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">What you are calling danger space was taught years ago but dealt more with machine guns then rifles, althought during the trench fighting of WWI it was also taught to rifleman. </div></div>

I did a little googling and came up with a book by CPT Eames of the 10th Infantry, where danger space was taught to US Infantry riflemen starting in 1907 at the Army Service Schools at Ft. Leavenworth, based on European work done 10-20 years previously.

CPT Eames apparently favored swept space over danger space.

CPT Eames' book, The Rifle In War, is available as a free pdf.