ACOG range estimation tricks?

[Greg Bell]

Hey guys,

I picked up a Ta-31 RCo M4 (the one for the 14 inch) and it is pretty dang neat.

I like how the BDC reticle has hash marks of diminishing widths to represent a man's width at the various ranges.

Does anyone have any links to any other range estimation tricks using the reticle?

[REDinFL]

I've not given thought to the alternative use of the gradiations but it occurs to me that one could use the vertical distances to estimate size and therefore range. For example, say the 500 yard mark is 50 moa below the zero, meaning approximately 50 inches. That would translate to 10 inches at 100, 20 at 200. One could use that in reverse to say that an object you would expect to be 30 inches high or wide fills the gap I'm using for the example means it is 300 yards.

Basically, take the trajectory chart for the calibration of the reticle, then reverse engineer it. A 50 inch drop at 500 yards means 50moa (yeah, I know, approximately; anything not using a high precision laser rangefinder is approximate, as is the eyeballing of any sizes), which means 10moa at 100. Simple arithmatic from there.

[ICANHITHIMMAN]

Greg

I have never needed anything more than the knowledge that the lines represent 19" the avarage width of a mans shoulders. That said I have a powerpoint around here some where, I got from a guy who was teaching the marines when they first started to buy the sights. Let me see if I can dig it up.

[Greg Bell]

That would be awesome. Thanks dude.

[JSantoro]

Think up common articles in the environment in which you shoot that are around 9.5" or 19" in width. Since a measurement is a measurement, and since we're talking range estimation, it doesn't have to be exact.

For example, when we kick RCO instruction, the lesson plan includes some examples, like a HMMWV wheel rim being 17".

I say 9.5" (round up to 10" for shits & giggles) because you can use the vertical line of the BDC and half of one of the range stadia, to estimate.

Doesn't HAVE to be width; go gangsta with the optic, you can go by height.

If you have the actual RCO reticle, you have horizontal milliradian stadia, hashed in 5mil increments. Keeping in mind that 1mil = 1m across @ 1000m, it's not too hard to math things out using WRM method.

One could say that I MIGHT know a guy with access to primary-source info.......

[Greg Bell]

Nice!

I do have the RCO reticle. I spent today using my Leupold range finder and trying to guess using my acog (which isn't mounted yet). Much fun!

[ICANHITHIMMAN]

Greg

No joy on the power point looked all over its on one of my flash drives sorry. Seams like some great info on the RCOs stads lines was just introduced however. I was not aware of their values.

[Zane1844]

Think up common articles in the environment in which you shoot that are around 9.5" or 19" in width. Since a measurement is a measurement, and since we're talking range estimation, it doesn't have to be exact.

For example, when we kick RCO instruction, the lesson plan includes some examples, like a HMMWV wheel rim being 17".

I say 9.5" (round up to 10" for shits & giggles) because you can use the vertical line of the BDC and half of one of the range stadia, to estimate.

Doesn't HAVE to be width; go gangsta with the optic, you can go by height.

If you have the actual RCO reticle, you have horizontal milliradian stadia, hashed in 5mil increments. Keeping in mind that 1mil = 1m across @ 1000m, it's not too hard to math things out using WRM method.

One could say that I MIGHT know a guy with access to primary-source info.......

Sorry to resurrect this three year old thread, however it was exactly what I was looking for, though I do need clarification:

What is 9.5" in the reticle? Is it the distance from each stadia line?

I am just trying to see if there are other ranging abilities with these BDC reticles since I have been looking at the VCOG.

[JSantoro]

Consider the 400m ranging stadia: The width of that line represents what something 19" wide would look like, through that optic, at 400m.

Half of 19" is 9.5", so I was speaking to use of HALF of any given range estimation line; each one is bisected by the vertical line that makes up the BDC.

EX: Say that somedood downrange of you, who you think you might want/need to shoot, is only showing his head. Figure that an adult male's head is something like 8"-10" across or front-to-back...

Ergo, if somedood's head fits the HALF of the 400m stadia, he's +/-400m away from you. If the head appears narrower than that, but not as wide as half of the 500m stadia, he's somewhere between 400 and 500m....and so on.

[Zane1844]

Consider the 400m ranging stadia: The width of that line represents what something 19" wide would look like, through that optic, at 400m.

Half of 19" is 9.5", so I was speaking to use of HALF of any given range estimation line; each one is bisected by the vertical line that makes up the BDC.

EX: Say that somedood downrange of you, who you think you might want/need to shoot, is only showing his head. Figure that an adult male's head is something like 8"-10" across or front-to-back...

Ergo, if somedood's head fits the HALF of the 400m stadia, he's +/-400m away from you. If the head appears narrower than that, but not as wide as half of the 500m stadia, he's somewhere between 400 and 500m....and so on.

Thanks!