Anyone know of a formula to calculate your hold under for depth shooting at distance? Trying to calculate what the hold under would be at distance for targets that have some depth in a room. Almost like a reverse loop hole but compensating for max ord. Not looking for someone to post the formula on the thread, just want to know if theres one out there and where I can look it up. Thanks
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Advanced Marksmanship Depth Shooting
- Thread starter drew1136
- Start date
Re: Depth Shooting
I'm not sure if this is what your asking for but here goes........
If you have all your dopes for let's say 100 to 500 yards and let's say they are in MILS ie;
100 zero
200. .3 MILS
300. .9 MILS
400. 1.6 MILS
500. 2.4 MILS
For example, if you have the above information, and all your targets are going to be within that 500 yards, I would set my dope for my 300 yard at .9 MILS. That is now my zero. Knowing that I can figure my holds for everything else.
Example;
300 yards -.9 MILS
200 yards -.3 MILS
.9-.3=.6 MILS
I would hold .6 MILS low to engage my 200 yard target with my 300 yard dope
300 yards - .9 MILS
100 yards - zero
I would hold .9 MILS low to engage my 100 yard target with my 300 yards dope
300 yards - .9 MILS
400 yards - 1.6 MILS
1.6-.9 = .7 MILS
I would hold .7 MILS high to engage my 400 yard target with my 300 yard dope.
Not sure if that was what your asking, but if it was, that's how you would do it.
I'm not sure if this is what your asking for but here goes........
If you have all your dopes for let's say 100 to 500 yards and let's say they are in MILS ie;
100 zero
200. .3 MILS
300. .9 MILS
400. 1.6 MILS
500. 2.4 MILS
For example, if you have the above information, and all your targets are going to be within that 500 yards, I would set my dope for my 300 yard at .9 MILS. That is now my zero. Knowing that I can figure my holds for everything else.
Example;
300 yards -.9 MILS
200 yards -.3 MILS
.9-.3=.6 MILS
I would hold .6 MILS low to engage my 200 yard target with my 300 yard dope
300 yards - .9 MILS
100 yards - zero
I would hold .9 MILS low to engage my 100 yard target with my 300 yards dope
300 yards - .9 MILS
400 yards - 1.6 MILS
1.6-.9 = .7 MILS
I would hold .7 MILS high to engage my 400 yard target with my 300 yard dope.
Not sure if that was what your asking, but if it was, that's how you would do it.
Re: Depth Shooting
Go to JBM and add the "danger space" information to the print out and it will give you the answer, you can then print and laminate it. It's free and very good and you can make it specific to your rifle / ammo combination providing you have good data to start.
Odds are, the room is not deep enough to matter if you look at the danger space, also it will give you the Max Ord heigh to work with so you can calculate the opening size, from there you can determine your information to clear the window.
The printout will be faster and easier than doing the math. Plus having the danger space is a nice way to set a BZO giving you the max information necessary to cover more ground. I used it this weekend at the K&M comp and engaged a series of UKD targets from 175 yards to 700 yards without ranging in a matter of seconds. It allows you to barely hold off the target without any thinking. I never had to calculate, just added after "X" distance, Very effective...
Go to JBM and add the "danger space" information to the print out and it will give you the answer, you can then print and laminate it. It's free and very good and you can make it specific to your rifle / ammo combination providing you have good data to start.
Odds are, the room is not deep enough to matter if you look at the danger space, also it will give you the Max Ord heigh to work with so you can calculate the opening size, from there you can determine your information to clear the window.
The printout will be faster and easier than doing the math. Plus having the danger space is a nice way to set a BZO giving you the max information necessary to cover more ground. I used it this weekend at the K&M comp and engaged a series of UKD targets from 175 yards to 700 yards without ranging in a matter of seconds. It allows you to barely hold off the target without any thinking. I never had to calculate, just added after "X" distance, Very effective...
Re: Depth Shooting
^^^^^^This^^^^^^^^
I use this on my ballistic cards as well. Very accurate if your input is correct, and takes the math out of it . I do recommend knowing how to figure it out on your own though.
^^^^^^This^^^^^^^^
I use this on my ballistic cards as well. Very accurate if your input is correct, and takes the math out of it . I do recommend knowing how to figure it out on your own though.
Re: Depth Shooting
He is looking to engage a target downrange on the other side of an opening with a target back some distance... hence the reverse loophole reference.
So he needs to know the impact point at the opening plus the distance beyond, then he can figure out the dope and hold necessary to clear the opening plus engage far enough back.
The danger space is the key, but there are other factors to consider. It's not straight hold over or under dope, and holding under is necessarily the answer. It can be solved without the formula.
He is looking to engage a target downrange on the other side of an opening with a target back some distance... hence the reverse loophole reference.
So he needs to know the impact point at the opening plus the distance beyond, then he can figure out the dope and hold necessary to clear the opening plus engage far enough back.
The danger space is the key, but there are other factors to consider. It's not straight hold over or under dope, and holding under is necessarily the answer. It can be solved without the formula.
Re: Depth Shooting
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">He is looking to engage a target downrange on the other side of an opening with a target back some distance... hence the reverse loophole reference.
So he needs to know the impact point at the opening plus the distance beyond, then he can figure out the dope and hold necessary to clear the opening plus engage far enough back.
The danger space is the key, but there are other factors to consider. It's not straight hold over or under dope, and holding under is necessarily the answer. It can be solved without the formula. </div></div>
LL, I'm picking up what your laying down
Wasnt entirely clear with his question, but you cleared it up. See, that's why you da boss man !
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">He is looking to engage a target downrange on the other side of an opening with a target back some distance... hence the reverse loophole reference.
So he needs to know the impact point at the opening plus the distance beyond, then he can figure out the dope and hold necessary to clear the opening plus engage far enough back.
The danger space is the key, but there are other factors to consider. It's not straight hold over or under dope, and holding under is necessarily the answer. It can be solved without the formula. </div></div>
LL, I'm picking up what your laying down
Re: Depth Shooting
che,
Look at the table from JBM, it explains it, a 308 175gr based off a 12" target, the better the ballistics the more forgiving the danger space.
che,
Look at the table from JBM, it explains it, a 308 175gr based off a 12" target, the better the ballistics the more forgiving the danger space.
Re: Depth Shooting
It has to do with your bullet drop and the range at which you can engage a specific size target without adjusting your dope or your POA.
If you are engaging a deer that has a vital zone with a radius of 3". If you type in your input into JBM with that vital zone, it will designate range in which you can engage that target without leaving that vital zone. I don't have my ballistic card on me at the moment, but JBM would give me a dope and a range. Let's say a dope of 2.5 MOA on my .308 with 175 gn SMK' on my rifle would enable me to engage a target with a kill zone of 6" out to 275 yards without having to adjust my point of aim or my dope.
That's why, as LL stated above, the flatter shooting the caliber, the less bullet drop you will have, and the greater the distance that can be engaged without changing your POA.
Does that make sense?
It has to do with your bullet drop and the range at which you can engage a specific size target without adjusting your dope or your POA.
If you are engaging a deer that has a vital zone with a radius of 3". If you type in your input into JBM with that vital zone, it will designate range in which you can engage that target without leaving that vital zone. I don't have my ballistic card on me at the moment, but JBM would give me a dope and a range. Let's say a dope of 2.5 MOA on my .308 with 175 gn SMK' on my rifle would enable me to engage a target with a kill zone of 6" out to 275 yards without having to adjust my point of aim or my dope.
That's why, as LL stated above, the flatter shooting the caliber, the less bullet drop you will have, and the greater the distance that can be engaged without changing your POA.
Does that make sense?
Re: Depth Shooting
Thanks guys I appreciate the help, Lowlight nailed it and is exactly what I was looking for. I just messaged you back on private mail as well.
Basically what I was looking for was a way to calcualte my hold under/over for a a couple of skeleton buildings in the area with rooms that are 8-10 feet tall and 20-30 feet deep ranging from 800-1000m. I was building a range card and wanted to try and calculate the dope for those engagments because they are a pretty high threat. I shouldnt have an issue getting the bullet on targetI just wanted to know roughly where I would be holding.
Thanks guys I appreciate the help, Lowlight nailed it and is exactly what I was looking for. I just messaged you back on private mail as well.
Basically what I was looking for was a way to calcualte my hold under/over for a a couple of skeleton buildings in the area with rooms that are 8-10 feet tall and 20-30 feet deep ranging from 800-1000m. I was building a range card and wanted to try and calculate the dope for those engagments because they are a pretty high threat. I shouldnt have an issue getting the bullet on targetI just wanted to know roughly where I would be holding.
Re: Depth Shooting
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dr Scholl</div><div class="ubbcode-body">Is this similar to point blank range? </div></div>
Yes
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dr Scholl</div><div class="ubbcode-body">Is this similar to point blank range? </div></div>
Yes
Re: Depth Shooting
In this case the key numbers are the size of the opening and the distance to the target from that opening. The actual question is, given a target at range X, 20 meters behind wall Y, with an open window of H x W, will my shot pass through the opening or impact the wall? It's like shooting under an overpass or tree at a target some distance beyond. You need to understand 'Where is the bullet along this path'.
A simple way to see this is to dial on the target elevation. Let's use my .308 and a target at 1000 yards. Let's say I need 10.6 mils up. The target is behind a bridge, but I have a full view of him under that bridge. The bridge is at 900 yards, so he's 100 yards past the bridge. What's the differance in elevation between 900 and 1000? If that point on the reticle is in the clear space under the bridge, we are good to go. If it's on the bridge, that's where the bullet will strike, no joy.
Adding vertical obstructions like the sides of a window or door frame, or the bridge pilings complicates issues by adding the windage hold as a problem. If I must hold 2.5 mils left for wind at 1000, where does that put the bullet at 900 as it passes under the obstruction? Now you need to figure how much drift is actually happening in that last 100 yards and see that you are clear on the left side of the obstruction. What's the wind drift value at 900? If that point on the reticle is clear of the left side of the opening, you should be good to go. There are some issues there with wind speed and direction, so I'd want some 'extra' room there to be sure.
If you know your dope and the ranges, and you have a calibrated reticle, you can do this on the fly without too much of an issue. Visualize the trajectory on the reticle and just keep the trajectory in the clear.
In this case the key numbers are the size of the opening and the distance to the target from that opening. The actual question is, given a target at range X, 20 meters behind wall Y, with an open window of H x W, will my shot pass through the opening or impact the wall? It's like shooting under an overpass or tree at a target some distance beyond. You need to understand 'Where is the bullet along this path'.
A simple way to see this is to dial on the target elevation. Let's use my .308 and a target at 1000 yards. Let's say I need 10.6 mils up. The target is behind a bridge, but I have a full view of him under that bridge. The bridge is at 900 yards, so he's 100 yards past the bridge. What's the differance in elevation between 900 and 1000? If that point on the reticle is in the clear space under the bridge, we are good to go. If it's on the bridge, that's where the bullet will strike, no joy.
Adding vertical obstructions like the sides of a window or door frame, or the bridge pilings complicates issues by adding the windage hold as a problem. If I must hold 2.5 mils left for wind at 1000, where does that put the bullet at 900 as it passes under the obstruction? Now you need to figure how much drift is actually happening in that last 100 yards and see that you are clear on the left side of the obstruction. What's the wind drift value at 900? If that point on the reticle is clear of the left side of the opening, you should be good to go. There are some issues there with wind speed and direction, so I'd want some 'extra' room there to be sure.
If you know your dope and the ranges, and you have a calibrated reticle, you can do this on the fly without too much of an issue. Visualize the trajectory on the reticle and just keep the trajectory in the clear.
