Field Target ranging with reticle

[shutik]

I'm math oriented person and numbers flow easy in my head. For those of you that like numbers, read on. If you are not numbers guy there might be simplification here.

As I've started shooting Field Targets I've realized that I need to know distance to the target in order to have best chance to hit it. I saw experienced shooters use expensive optics with huge side wheels to find focus with paralax adjustment and derive distance from it. The problem starting shooter runs into is their scope does not range that well with paralax. And even expansive ones shift focus with temperature changes. But there is another way.

Know your angles. You will need the scope that has markings, MIL dots, MOA, some lines. The idea is to derive distance to the target using little math from trigonometry class. So, after observing some metal field targets I've measured they all have same 8 inch base. That will be small cathetus of right triangle. Looking thru the scope at the target we can determine angle that spans those 8 inches and with this information we can compute distance to the target, which is second cathetus of this right triangle.

For my scope, which has markings in MOA I added table print out that tells me how many MOA 8 inches span at every yard from 10 to 55.

10 - 76
11 - 69
12 - 63
13 - 58
...
20 - 38
25 - 30
35 - 21
40 - 19
45 - 17
50 - 15
55 - 14

Now I can look thru my scope, count the markings, look in the table and know my distance, Ha.

 

[rich177]

this is very interesting. Some of the hunter division shooters do a similar ting but they call it bracketing. It works very well if all the targets or bases are the same. The fly in the ointment is that we use 13 different kinds of field targets and maybe six different base setups. Different clubs use even other different setups.
Having said that it is still a valuable tool to determine distance and can be a great cross check with your scope parallax readings.
Rick

 

[John "spysir" Blount]

Bracketing works well with practice. Do keep min mind you wont always be ablke to see the bases tho.
You pretty much know the KZ size on all targets ( =/-) you might try just knowing your total drop from you zero to 55 yards. If you know your drop is say 1=1/2" at 55 and the KZ is 1 1/2" just aim a touch above the KZ. More of a poa trick than ranging but it figures in there.

The old Hawke SR6 is great for Hunter ( and bracketing ) if you can find one.

I dont recall the circles size at ranges but the lines were all at 5 yard intervals.

John

 

[shutik]

Yes, this is bracketing.

Yes, you need to know your target sizes, or base size or brick size that is placed in front sometimes.

I just wanted to point out that you can use any scope that has line markings, just need to figure out what those markings are and write down how many markings cover known distance at different yardage.

This assumes you already know hold over for different distances and use bracketing to determine correct hold over point.

 

[Xbowsniper]

All,
I'll be doing an episode on my Field Target Tech Channel on U Tube on optically centering a scope, among some other scope info for target shooters. This episode will be posted sometime Saturday. There has been a large amount of requests for me to cover this, I'll most likely expand it to at least 2 episodes on scopes, possibly a 3rd in order to cover mil dot calculations, and bracketing in different ways, particularly for use in Hunter class.

Tom Holland 
[email protected] 
Assistant Match Director 
Eastern Suffolk Competitive Airgunners Association (ESCAA) Long Island NY escaaclub.com 

 

[shutik]

Thanks Tom, we are fortunate to have you cover field target. Learning a lot from your videos.

Further wanted to add that math comes from similar triangles and could be applied based on rules of proportions:

See my poor paint diagram:

We are standing at point A and trying to measure angle alpha.

AB is reference distance 100 yards, CB is reference height for the angle. 1 MIL = 3.6 inches at 100 yards, 4 MOA = 4.188 inches at 100 yards
EF is our object in the scope. If we look at it and see it measure 36 MOA and we know it is 8 inches long, then proportion equation is: CB/EF = AB/AF
AF = 100 / ((36 * 1.047) / 8) = 21 yards

 

[Xbowsniper]

Shutik,

I'll be the first one to tell you, and everyone else, that I am the ultimate math MORON!.... and I'm not afraid to admit it.
This is relatively simple math, I'll get into it briefly in one of my upcoming scope videos, and I'll also cover how to range find more accurately by using different magifications as well. I'll also explain why this math only works with a 10x scope, unless it happens to be a first focal plane scope, which the math SHOULD work, I have seen some cheaper first focal plane scopes not work as well.
Stay tuned, as iI said, most likely the next 3 episodes will be on scopes.

Tom Holland 
[email protected] 
Assistant Match Director 
Eastern Suffolk Competitive Airgunners Association (ESCAA) Long Island NY escaaclub.com 

 

[gonzav71]

Here's a simple version for the field target game. You can measure the object using the reticle at a certain distance and making note of it. It's all about ratios.
​For example, if you measure the size of the kill zone (1.5") at 50 yards with mil-dots at 40x scope magnification, you get about 2 mil-dots. Then if you bracket a another unknown target with 1.5" kill zone and you measure less than 2 mil-dots. That gives you an idea that the target is greater than 50 yards and can be set at the maximum distance 55 yards.
​If you measure the 1.5" kill zone and you get 4 mil-dots, then you know that distance is about 25 yards.
​If you measure the 1.5" kill zone and you get 3 mil-dots, then you know the distance is about 37.5 yards.
You do not have to remember every distance and size. Again, it is all about ratios.
Most 12x or 16x scope for Hunter Class Field Target can range find well out to 35-40 yards using parallax adjustment.
It is just the distances past 35-40 yards that bracketing should be used as a backup tool.
Buy a small pocket notebook and write down the distances and mil-dot measurements when you are looking at the targets at specific distances especially 40 yards or longer.
​One thing I found out that I cannot hold steady enough to measure (bracket) accurately when sitting in (field target) position.

Keep it simple.

 

[Scotchmo]

Ranging with reticle
Bracketing
Stadiametric rangefinding
...all the same thing

Knowing the math makes it more versatile, but you don't need to do any math to take advantage of it. And you don't need to run at 10x to take advantage of it. If you want to do the math, you'll need to know the sub-tensions of the reticle. It does not matter if it's milliradian, MOA, or any other angle. If you know the sub-tensions at a particular scope setting, and know how to do the math, you can do it.

If you have a single feature that you want to range at all distances, and you abhor doing the math, you can still range find via reticle. Say that you shoot at a range that uses cinder blocks to support targets and sometimes they are visible. That means that the cinder block it's a good candidate to learn when shooting at that venue. Place a cinder block at 55yds. Counts the reticle sub-tensions that span the cinder block. Write it down. Now move it to 54yds, and then 53yds, etc. Each time, carefully counting the the sub-tensions when viewed through the scope. Eventually you have a dope sheet that can be used with your particular scope and cinder blocks. You can do the same for target bases, signs, hit zones, 2x4's or anything else that you commonly see near a target.

I focus rangefind when I need to, but if I see an obvious (or not so obvious) feature that I have documented in my dope-book/sheet, I'll use it. Especially for far targets.

I do the math in a spreadsheet with the sub-tensions for a particular scope already entered. Adding a new feature to bracket is simple. I just add the feature & dimension to a column and the spreadsheet calculates the rest.

There is more to it than having the dope or doing the math. You must also get an accurate count across a feature when viewing through the scope. Some people have a tough time with that. It takes practice to it well. If you normally use mil-dots for hold-off plus holdover, it's similar to that. If you're only comfortable aiming at a clicked in target, you'll have to learn how to hold steady and scan the reticle, either left to right for horizontal features, or up and down for vertical features. And do it without pulling the start of the bracket out of position when you scan. When shooting, you normally only have to concentrate on one point. With bracketing, you have two points to deal with. I'll typically scan and count two or three times to get it right. If you are steady enough to hit the target, then you are steady enough to bracket.

I needed more than the 25 yards in my backyard in order to complete my scope calibration. I was out at the range today verifying the sub-tensions of the reticle on one of my supposed 16x scope. When set at 16x and focused at 50 yards, this scope is really giving 14.7x. At close range, the sub-tensions indicate it is 15.5x. Most scopes exhibit this peculiarity. So that is something else to be aware of. Changes to magnification will alter the sub-tensions. And changes to focus can alter the magnification. This scope just happens to be worse than most. But as long as I know the discrepancies, my dope can account for it.

 

[josh3rd]

Awesome write up

 

[Motorhead]

AND ... in AAFTA rule FT you legally ONLY GET 5 minuets once seated / handling your gun to get all the ranging, math, wind doping & fussing about PLUS actually take the 4 required shots.

See many folks who struggle with this, as well see folks disregard this rule entirely taking much longer.

 

[Scotchmo]

AND ... in AAFTA rule FT you legally ONLY GET 5 minuets once seated / handling your gun to get all the ranging, math, wind doping & fussing about PLUS actually take the 4 required shots.

See many folks who struggle with this, as well see folks disregard this rule entirely taking much longer.

I have struggled with the time constraint in the past, but it was never from ranging or bracketing. I don't think that's where the time constraint is a problem. For me, running the clock out has never been an issue when the target is visible. Targets that are clearly visible from all shooting positions speed up the match progression. But then there are those that like to wait out the wind or just have trouble pulling the trigger.

Ranging with the reticle can be just as fast, or sometimes even faster than focus range finding.

 

[dan_house]

One thing Ive learned from Scotchmo at matches...... he had (or at least used to) quite a list of objects likely to be seen at a FT match. and a list of the common dimensions of many FT targets available. SO ive started doing that too, just not to the depth he has.

When I set my scope up, Ill set a target board out at a given distance, focus the scope on it, and mark yardage on the wheel. Also on that board is a 3/8, 1/2, 3/4, 1, 1.25. 1.5, 1.75 and a2 inch circle. Also the dimensions of an american soda can, width of duct tape, lines that correspond to common features on my Gamo targets (base plate, hinge, distnace of string atttachment pont to the bottom of the base plate), 2x4,2x6,2x8 lumber, a golf ball, common Cinder blocks, T posts, and others I can remember (havnet done it year this year). I record the Item and its size, then the size alone and its "size" against the reticle at a given distance.

Not everything will have an entry for some distances..... the 3/8 circle wont have an entry past about 37 yards and the Gamo base wont have one until about 25 or so yards...... 

I dont rely on this, rather use it as a way to confirm my focus ranging. If they are greatly out of agreement, then Ive done something wrong ranging it.



Yes its a lot of work. But its a great way to be outside, and the back and forth moving my target board gets my off my butt and moving. I usualy start around 1 pm DST and go until I notice the afternoonlight has changed colors. It usaully takes a couple afternoons to get 10-55 data. The other issue is HOW to present this data. Thatll be a personal preference, but IMO the more data the better...... 

 

[shutik]

If any of you guys can share dimensions of bases of commonly used field targets, i would really appreciate it.

I have measured Crosman zombie, it is 7 1/4 inches at the base. Big cinder block is 7 5/8 inches.

I'm looking for actual measurements of Gamo bases, air Venturi bases and any other bases you have. Also for tips on how to tell them apart.

Thank you, Vasyl.