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Flatness of trajectory

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  #8  
Unread 06-26-2004, 10:58 AM
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Re: Flatness of trajectory

Newbie,
Interesting thread! My head demonstrated rather low bandwidth reading all this -had to re-read everything a couple of times to get the issues straight in my head!

Range (mis)estimation would appear to be the root of all problems that could arise in your scenarios. Determining the opening range shouldn’t be an issue if you have a laser; issues may arise if the target should move closer/further between obtaining the opening range and your 1st shot or between 1st and subsequent shots.

If range (mis)estimation –for whatever reason- is of concern to you, I think what you’re after is the round that gives you the ‘least plunging’ trajectory at the ranges at which you are likely to shoot (ie what you’re describing as the greatest ‘danger space’.)


GEG,
I must say that I too was a little confused by the use of the term ‘danger space’ here.
It is a military term used in the context of machinegun or harassing sniper fire.
It’s similar to the idea of ‘beaten zone’ but takes account of targets being vertical rather than horizontal; so (in very ballpark terms) with a centre hold on an avg 5.5ft man, the danger space for a 308 with sights set at 800yds would start if he was actually standing at 700-and-a-bit yds (ie the trajectory would start to clip the top of his head) and end if he were actually standing at 850-and-a-bit yds (ie it would clip his toes).
I think what’s being referred to here is ‘the ranges between which the trajectory will remain in the animal’s vital area at a given sight setting’ which is not the same as the military concept of ‘danger space’, but ‘danger space’ certainly sounds sexier! [img]images/icons/smile.gif[/img]

Dave,

Is this a warm-up for some more ‘Rotation of the Earth’ stuff?!

[ 06-26-2004: Message edited by: Brown Dog ]
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  #9  
Unread 06-26-2004, 03:54 PM
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Join Date: Jan 2004
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Re: Flatness of trajectory

Danger Space is the portion of the projectile's path before and after it's "zero" point where it does not rise or fall above or below the target by an amount in excess of the specified kill zone. For example, if the specified kill zone is 12 inches and the rifle is "dialed in" to hit approximately dead on at 700 meters, the Danger Space would be equal to the amount of distance on each side of the target where the bullet is no more than 12 inches above or below the target.

Edited: Sorry Brown Dog, I didn't see that you had already explained the concept before I posted my response.

[ 06-26-2004: Message edited by: Newbie_71 ]
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  #10  
Unread 06-26-2004, 06:46 PM
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Re: Flatness of trajectory

Brown Dog

How'd you know that???? Do I telegraph that openly??

I was out for a walk on the Appalachian Trail (AT) today thinking on this problem "Danger Space" and just might launch into a deep discussion at any moment... how about now!!

Like you state, for the military and their seemingly vertical targets there is more apparent danger space for the common shooter/rifleman. For hunters and the more horizontal targets (sorry, they're not really JUST targets but I'll call them that here for ease of discussion). I got to thinking I could put together a little program or spreadsheet that a user could calculate ballistic trajectory and also enter the targets' kill zone size and get an answer back for the Danger Space limits. Sounds like a worthy puzzle and deviation.

Newbie_71

Have we come close to actually answering your question?? If not let's finish that up and maybe continue on with this danger space thing. Thanks
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  #11  
Unread 06-28-2004, 02:58 PM
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Re: Flatness of trajectory

Dave King,

Do you consider "Danger Space" of much relevance at all to civilian long range shooting? Do you know if it of much significance in regards to sniping?

What I'm mostly been thinking about is which rounds will allow for the most tolerance in regards to distance approximation errors. For example, if the target is 500 yards away, what rounds will "forgive" the most in terms of how far away the approximation is. I've noticed that there are instances where a round with more actual flight time (and correspondingly more bullet drop) will actually allow for more error while still maintaining shot placement in the specified kill zone (even though this usually means you will have to crank your scope a little more) and whether or not others consider this to be as significant as total bullet drop and/or the number of click adjustments one must make on his scope.
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  #12  
Unread 06-28-2004, 03:19 PM
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Re: Flatness of trajectory

Newbie_71

I'll get back to you on this in a few hours. We do of course consider "danger space" when we hunt ( the use of the term "continuous danger space" could be loosely considered the MPBR term hunter typically use). We're not often concious of it when we hunt short range if there's considerable excitement but most long range guys adjust their data as the critter approaches or recedes from the hunter.


All

Here's an article on differing terms including "Cone of fire", Beaten zone" and "Danger space".
http://www.leatherneck.marines.usna....Pubs/b2107.pdf
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  #13  
Unread 06-28-2004, 06:47 PM
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Re: Flatness of trajectory

Newbie_71

Your question:

"Do you consider "Danger Space" of much relevance at all to civilian long range shooting? Do you know if it of much significance in regards to sniping?"

Because most folks aren't worried about being shot (or shot at) by the critters they hunt there often isn't a tremendous amount of concern about a first round hit. That's not to say that there isn't a group of us that are first round hit hunters but we do have the luxury of making a second shot in most cases. In sniping (in the military manner) it's of considerable importance IMHO.
We have the luxury of ranging our target(s) but there is some error in the system(s). Lasers that range background objects vice the actual critter are a problem, MilDot ranging on critters of estimated size also introduces an error in range. Once the range error exceeds the danger space things get a little dicey.

For example: That 308 round at 2580fps, 175 (.498 BC) @ STP. Use a 12 inch kill zone size (two dimensional target) and we have a continuous danger space (MPBR) of 340 yards with a 290 yard zero. (Pretty good so far.) BUT move that critter to 500 yards and you now have a danger space 55 yards deep (470 to 525). Now well head out to 650 yards (my max range) and the danger space is down to 30 yards deep (635 to 665). 1000 yards and well have just under 16 yards of danger space (991 to 1007) (for comparison a military sniper would have about 46 yards of danger space for a 36" torso hit).

The error rate for laser ranging 1000 yards is +-1 yard for instrument (as stated by manufacturer I believe). Making sure we've collimated our laser and are actually ranging the critter at 1000 yards is another matter but we only have about 15 yards to play with, 7.5 in front and 7.5 behind, pretty close measurement for 1000 yards. What does this mean??? It's pretty difficult to keep this in mind when shooting and it's just a little too much info for most folks. I guess it's like walking a tight rope, we don't care what's on the sides or how far down it is as long as we stay on the rope.

Little side note: If we push that same bullet to 3150fps the 1000 yard danger space opens up to about 26 yards...this is a good sell for a magnum chambering.


"What I'm mostly been thinking about is which rounds will allow for the most tolerance in regards to distance approximation errors. For example, if the target is 500 yards away, what rounds will "forgive" the most in terms of how far away the approximation is. I've noticed that there are instances where a round with more actual flight time (and correspondingly more bullet drop) will actually allow for more error while still maintaining shot placement in the specified kill zone (even though this usually means you will have to crank your scope a little more) and whether or not others consider this to be as significant as total bullet drop and/or the number of click adjustments one must make on his scope."

For any given BC the faster you push the bullet the greater the danger space you'll have. If it's dissimilar bullets you'll need to run the numbers but no matter the muzzle speed of the lower BC bullet the greater BC bullet at lower speed (within reason) will eventually beat it out in danger space.
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  #14  
Unread 06-29-2004, 05:01 AM
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Re: Flatness of trajectory

Wow, this is deep and meaningful stuff here . How about a .22/250 Ackley shooting 80gn VLD's at about 3300 fps or a .243 AI , 6mm AI or 6mm/.284 shooting 95gn VLD's at 3300 - 3400 fps. BC's in the .520's . Danger space is pretty long all the way out yonder . Barrel life should be o.k. (compared to big .30 cals + anyway). Plenty of grunt for varmints to 1000yds plus.
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