Effective target size given bullet apex

[chootem]

That title may not end up being accurate, but it's the best I could come up with given what I'm interested in understanding better. I know there are some super smart people here who probably know this already or possibly some folks who have wondered what we were pondering. Similar conversation to the PRS guys wanting flatter caliber choices, but I've not heard any of them talk the math out other than 'flatter and more hits'.

A few of us were shooting the 2k steel the other day and afterwards we brought up the same old discussion about the 'effective' target size from a pill coming in at say a 150ft apex for example on to a 60"x60" target. When we are all over 20mils regardless of calibers available to the various guys on the 2k line we got to wondering what the actual difference was b/t a 6.5 or a 300NM/338/375 etc

To put it another way let's say you are a bug riding the nose of that bullet from apex as is begins it's trip down to the 60x60 steel.....seems to me he would not be seeing a full 60"x60" steel target but something that looks a lot smaller? Is there a mathematical formula for calculating this effective target size?

Apologize if I butchered that description and this isn't mission critical just a question that lingers repeatedly. Thanks

 

[SKWERLZ]

Unless you’re talking the scoring advantage on paper that certain BR shooters love 30 BR for I see target size as more to increase hit percentage regardless of bullets size.

Here’s my two favorite 2k targets.

When you start getting into pretty extreme decent angles like 2 miles and beyond I suppose the bullets eye view is certainly different as it’s coming in at a 30-40 degree or more but I still keep target size the same.
My biggest is 30”x30”

My 338 drops 41” per ten yards getting to these plates at 2020 yards.

It’s dropping 78 inches per ten yards get to my 2 mile plate.

Someone far smarter than me could easily figure out the angles of approach.
I have seen steel for ELR angled up a bit to compensate

 

[chootem]

That's pretty much what I was getting at the decent angle, but it's all relative to what bullet is being fired and at what distance hence why I was looking for some kind of mathematical formula. There was everything from 140g to 300g being shot the other day. At 2k we have 2 each 60"x60" and a 36"x36" and yea it's dramatic the hit rate increase with the boomers, but still fun to stretch out the smaller stuff on occasion.

 

[SKWERLZ]

That's pretty much what I was getting at the decent angle, but it's all relative to what bullet is being fired and at what distance hence why I was looking for some kind of mathematical formula. There was everything from 140g to 300g being shot the other day. At 2k we have 2 each 60"x60" and a 36"x36" and yea it's dramatic the hit rate increase with the boomers, but still fun to stretch out the smaller stuff on occasion.

I’m not sure if my math is right but I’m getting approximately 6.5degrees for 2020 yards
12.23 for 3520 yards
17.14 for 4100 yards
This is for my 338 with some high BC solids.

 

[FeMan]

I’m not sure if my math is right but I’m getting approximately 6.5degrees for 2020 yards
12.23 for 3520 yards
17.14 for 4100 yards
This is for my 338 with some high BC solids.

That's what I come up with and that translates to an effective target heights of 27", 24", and 21".

 

[FeMan]

To the OPs question, the approach angle matters for sure. If you took the time to calculate the differences in effective target height out for different bullets, I am not sure it would be nearly as significant a factor in determining hit percentage as ES/SD. The BC and time-of-flight creating horizontal dispersion are the real factors in shooting at those distances (unless you have a true dead calm condition) and that's more of the reason the bigger calibers and higher bc bullets shine.

 

[chootem]

To the OPs question, the approach angle matters for sure. If you took the time to calculate the differences in effective target height out for different bullets, I am not sure it would be nearly as significant a factor in determining hit percentage as ES/SD. The BC and time-of-flight creating horizontal dispersion are the real factors in shooting at those distances (unless you have a true dead calm condition) and that's more of the reason the bigger calibers and higher bc bullets shine.

Wow thanks guys really appreciate you indulging the big dummy here. Could I please trouble you guys to fill in the blanks(at least that I'm not reading)on the math equation so I can share this with a few friends?

For instance I was dialing 29.5mils for 2000 yards on a 60" x 60" target. 1 mil at 2k is equal to 72", correct or no? So 29.5mils dialed would be 2,124" or 177' at apex for bullet on way to 2k? Thanks again for your knowledge sharing.

 

[SKWERLZ]

Wow thanks guys really appreciate you indulging the big dummy here. Could I please trouble you guys to fill in the blanks(at least that I'm not reading)on the math equation so I can share this with a few friends?

For instance I was dialing 29.5mils for 2000 yards on a 60" x 60" target. 1 mil at 2k is equal to 72", correct or no? So 29.5mils dialed would be 2,124" or 177' at apex for bullet on way to 2k? Thanks again for your knowledge sharing.

Look at your ballistic solver
It will tell you those things.

My 338 with 17.7 mils at 2000 drops 1268 inches.
To figure out approach angles I calculated the fall at a certain distance and it’s point 1 yards before then figured out the angle that trajectory created.

 

[Jeff Porter]

Are you asking what the "apparent" target size is looking from the bullet at different incoming angles to the target? i.e. - 0 degrees - flat lazer beam you have the whole target height - say 2 mil. From directly above 90 degrees up from the target, you only have the thickness of the target to hit.

Like looking at a baskeball hoop from 10' straight in you only see an orange line but an arced shot coming in has the whole 18" to drop the 9.5" ball through?

I do not have the answer but wanted to make sure I understand you question.

 

[kzin]

Wow thanks guys really appreciate you indulging the big dummy here. Could I please trouble you guys to fill in the blanks(at least that I'm not reading)on the math equation so I can share this with a few friends?

For instance I was dialing 29.5mils for 2000 yards on a 60" x 60" target. 1 mil at 2k is equal to 72", correct or no? So 29.5mils dialed would be 2,124" or 177' at apex for bullet on way to 2k? Thanks again for your knowledge sharing.

I think you're confusing aim over with bullet apex.
You need to aim the bore 177' above the target at 2000
But the actual 'hump' of the bullet is only about 61'
Apex at about 1200
so 61' ft of drop over 800yards/2400 ft
around 1.4 degrees average but steepest at the target end


That's using a ballistics calculator for the trajectory
I could do the equation for a vacuum on paper but it's much harder if you'll be shooting in air

 

[6bra1k]

That title may not end up being accurate, but it's the best I could come up with given what I'm interested in understanding better. I know there are some super smart people here who probably know this already or possibly some folks who have wondered what we were pondering. Similar conversation to the PRS guys wanting flatter caliber choices, but I've not heard any of them talk the math out other than 'flatter and more hits'.

A few of us were shooting the 2k steel the other day and afterwards we brought up the same old discussion about the 'effective' target size from a pill coming in at say a 150ft apex for example on to a 60"x60" target. When we are all over 20mils regardless of calibers available to the various guys on the 2k line we got to wondering what the actual difference was b/t a 6.5 or a 300NM/338/375 etc

To put it another way let's say you are a bug riding the nose of that bullet from apex as is begins it's trip down to the 60x60 steel.....seems to me he would not be seeing a full 60"x60" steel target but something that looks a lot smaller? Is there a mathematical formula for calculating this effective target size?

Apologize if I butchered that description and this isn't mission critical just a question that lingers repeatedly. Thanks

all i know is we shoot 2k group and score and are at about 12 inches for 5 shots

 

[NZ_Fclass]

You may have the wrong end of the stick here. I don't shoot PRS - but for precision score matches, the target MUST represent the accuracy of the guns used, and the capability of the expert shooters.

Take FTR - with a half MOA x ring, the rifle and I mean a target rifle, built for the task, in perfect conditions, be capable of putting all the shots within the ring. Grandad's ole thunderstick will not, making it unsuitable for the match. The same scenario works in reverse - if the target was smaller, the "possible" would not be achievable, even with the best rifle and ammo. The target must be capable of being shot, without ANY LUCK being involved, by a first class shooter with a first class rifle.

When the UIT rapid fire match target became too "easy" and 600's were being shot, the target and the pistol spec were changed. Guns (and top shooters) exceeded the target. This happened many times from the early Olympics when the match was shot with a service revolver and the target was a man sized thing, through 22 short pistols with ported barrels and "wrap-around" grips, to it's current form with the standard rapid fire circular target and a Standard pistol in 22lr. - the same pistol spec as the Ladies 25m match and the Standard Pistol event.

Target and match design should reflect the capability of the firearms specified and a perfect score must be achievable.

 

[Racingjoe27]

Bryan litz posted on IG about “danger space” a few weeks ago.

In his words, danger space is the distance around your target through which the bullet trajectory remains in the vital zone (or in this case, a 60” elevation window).

He goes on to say, you can look at danger space in ballistic tables by setting the increment to 1 yard and setting the zero range at your target distance.

While this doesn’t tell you the effective target size for the bullet approach angle, it will give you an idea of how sharp of an angle based on the size of the danger space. It will also let you know how accurate your ranging needs to be.

Take a look at the danger space for the different cartridges on the line, maybe that will give you an indication as to why the “boomers” have a dramatic increase in hit rate