Drop versus holdover

[tpcollins]

Just for an example - if I’m zeroed at 100 yards and the ballistics chart says I have a 5” drop at 250 yards, wouldn’t holding the crosshair 5” high on the target at 250 yards hit the bullseye? Thanks.

[Tawaliga]

Correct, but then how are the optics companies going to get more money from your account into theirs?

[Nathan]

Yes. How do you measure that 5”?

How do you measure when it is 315 in @ 1000yds?

[tpcollins]

Originally Posted by Nathan

Yes. How do you measure that 5”?

How do you measure when it is 315 in @ 1000yds?

I’m only concerned about holdover - or with a BDC reticle - at 50 yards with a 30 yard zero. Thanks.

.

[44 AMP]

Yes. How do you measure that 5”?

5" or 5 feet, you measure it the same way, by eye and you guess. Or if you're more precise, you "estimate".

First off, you need to know the range, with reasonable accuracy. Being off by even 50yards (or sometimes even 25yds) can make a significant difference in the drop, depending on the bullet's velocity at that range.

and you need to know the drop characteristics of what you are shooting. Huge difference between a .45-70 and a .300 Mag.

OK, so you know the range, and you know the drop (and we'll leave wind drift out of this for the moment) then is it a "simple" matter of adjusting your point of aim to compensate.

Lets take your 5" drop, as the example. One way is to crank in 5" more elevation on your scope (or iron sight if it will do that) and then aim dead on target.

The other way is to aim those 5" above where you want the bullet to hit. I include holdover (or under) in the term "Kentucky windage" but some do not.

Point here is that holdover is almost never as precise as adjusting the scope, but it is FASTER, and your sights remain zeroed where you set them. You don't have to crank them up for the shot then REMEMBER to crank them back down to the original setting.

They way its most often done is to use the size of a known object for reference. This includes the game you are shooting at. IF you know, for example that, broadside, the deer is 12" (roughly) back to belly, and you need to hold 5" high, then you hold just a touch less than "half a deer high" and your bullet should land in the boiler room.

ANY object at that distance that you know the size of can be your reference. For example, if you know that the fence post the deer is next to is 5 feet high, you can estimate fairly well down to half a foot or so.

Of course, this takes practice and different people will be differently skilled doing it, but its easily done, and has been done since people started launching things at game, or each other. Archers are skilled at estimating range and drop of their arrows the same way. The ones who aren't are considered poor archers.

And, speaking of which, a friend of mine who was a bowhunter spent all summer practicing in his backyard for the "40 yards shot", determined to get his deer. That fall, the deer jumped up 25yds from him, and he did what he's spent all summer practicing. And shot right over the deer's back...

The same principles apply to any and every ranged weapon. (in earth's gravity well, at any rate...)

[Plainsman]

This is why the mildot reticle exists!

[Drm50]

I use old Lyman micrometer receiver sights on several rifles. I sight in rifle and mark witness plate for known distances. Works well if you are decent judge of distance or shooting known ranges.

[hounddawg]

I tend to use "Kentucky windage" or "shading the shot" and scope adjustments on a 50/50 basis when target shooting over wind flags. Of course that is on known size stationary targets not a moving animal at an unknown distance.

[44 AMP]

Assuming there is sufficient adjustment in your scope or sights, adjusting the sight for drop is fairly simple and quick, and usually more precise than estimating the hold over.

BUT

There is an important thing that must be done, and often is forgotten. And that is putting the sight / scope BACK to its original zero setting after making the shot. Particularly when hunting! Its an easy thing to forget, after you've 've made your shot, but if you don't reset your scope to where it was zeroed, the NEXT time you shoot, (at a different distance) or adjust it for drop you're going to be WAAY off.

If its your habit to adjust the your scope to compensate for drop on the shot, then ALSO make it your habit to return the scope setting to where it was before you adjusted it. Do not pass GO, do not collect $200, do not do anything else not vital before resetting the scope. Otherwise, your next shot is very likely to be a miss.

And, if you're like some of us, and say. "well, I'll do it later" often later, we forget to do it. or think we did it, when we didn't. Either way, next shot at any different range is going to be a miss.

Some folks make a "witness mark" on the sight.scope for the "zero" setting. THis allows you to see, at a glance if your sight is set where you expect it to be.

Personally I rarely adjust the sights I "guesstimate" the hold over, and so my sights remanin of their zero, which is a useful thing, for me.

[Rob228]

This is also where first focal plane reticles come into play. With a second focal plane reticle the reticle changes size when you change the power of the scope (which is why for the longest time you saw fixed 10X scopes on issued sniper rifles/DMRs). With a first focal plane scope 5" on the reticle is always 5" no matter what power you have the scope set to.

If you've just got a Duplex reticle you're going to have to get good at figuring out the size of the target in the reticle based on what distance you are shooting, and from there you can estimate the 5" holdover.

[jmr40]

Let's not over complicate this. Five inches of drop is no biggie. Virtually all common hunting rifle cartridges zeroed at 100 yards will be 2-3" low at 200, maybe 5" low at 250 and around 10" low at 300 yards. It is only well beyond 300 yards where drop and accurate range estimation becomes critical.

You also have to consider that a typical deer has a 10-12" kill zone. An animal like elk is 18-24". If you're deer hunting and estimate a deer is less than 200 yards away just hold where you want to hit. You'll be within 2-3" with a 10-12" bullseye.

If you estimate somewhere between 200, but no more than 300 yards leave a little daylight between the horizontal crosshair and the animals back. Even if your estimation is off by 50 yards any animal between 250-350 yards is going to be hit in vitals.

It is only when you get close to 400 yard shots that you really need to worry. At that distance accurate range estimation via a range finder is critical. Along with a scope that can compensate for drop.

Second focal plane scopes aren't a handicap for hunters. Zero the scope on max magnification which is 7-10X on most hunting scopes. Just keep the scope on the lowest magnification for close shots and use the max magnification, (the one you used to zero) for longish shots. Simply ignore anything in between and this is never a problem.

Where first focal plane comes into play is with target scopes with 20X or more on the upper end. You'll often run into an issue where the max magnification is too much, and the lowest isn't enough. It is only when using those in between that there is a problem.

[Rob228]

^^^^

That is some good advice right there.

[44 AMP]

You should get a mildot reticle

Most of us aren't well versed in mils, which are not the same as inches.

The mil-dot reticle does provide additional aiming points, but unless you are using exactly the cartridge and load they are calibrated to, you'll have to do some range testing to find out exactly where your rifle hits when using them as aiming points.

[tangolima]

If it is close, no need to hold. Beyond that, to hold or to adjust.

Can't practically adjust the scope's elevation on the fly, unless you have "tactical turrets". It kinda narrows down.

For a lot of scopes the only practical solution is to hold. How to hold is then the question. There are more than one way. Better way is use reticle "features" to help estimate. You can do a lot of things even with duplex reticle posts and magnification settings.

-TL

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[JustJake]

This is why the mildot reticle exists!

Actually it’s why Mil/Mil scopes exist.

A Mil is always a Mil, and with a Mil/Mil optic no extra seconds are spent figuring the MOA —>MIL “conversion” in your head, ... which for your average deer-camp Fuddly just gives him a bad migraine. Meanwhile, the critter in his reticle gets bored waiting to be shot and scoots away.

Noop. Mil/Mil is the way to roll, just like the Navy Seal snipers do, and “range-ess” (range estimation) is something you only get good at by practicing it.

With a confirmed, basic 100-yd zero, you then vet your rifle at other incremental distances (200yds, 300yds, 400yds, etc) by figuring the Mils to the target at those distances, using the hashes on the reticle below the center cross-hair. Then you know what hold-over hash in the reticle corresponds to getting a hit on the target at a given distance. Yes, you might actually have to shoot more than a few rounds to vet all this.

Once done however, and you’re out in the field, if a shootable critter suddenly appears beyond 100yds, you just put the hold-over hash on it that corresponds to that distance, and send a round into its vitals. (Again, why having solid range-ess skill is critical). This also assumes no shooter-induced error, also known as “fuglying the shot.”

Now if the context is your average deer-camp Fuddly up in a Midwest tree stand, where 99.9% of his shots will be inside 75yds, none of this high-speed, Mil/Mil, Navy Seal sniper stuff matters.

[Bart B.]

There's 3 or 4 standards for the miliradian.

http://wndsn.com/?d=metrology/MIL_vs...s_NATO-MIL.txt

Which one is used in the USA shooting Sports?

[tangolima]

Radian or radion?

1 meter out of 1km is one mili-radian or mil. If one wants to go mil, it would be the best to go meter instead of yard. Mil reticle with moa clicks is signature of cheap scope. Better scope has 1/10 mil clicks.

-TL

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[Bart B.]

Originally Posted by tangolima

Radian or radion?

1 meter out of 1km is one mili-radian or mil. If one wants to go mil, it would be the best to go meter instead of yard. Mil reticle with moa clicks is signature of cheap scope. Better scope has 1/10 mil clicks.

-TL

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I disagree.

[Bart B.]

All internally adjusted scopes have a few percent spread of LOS change per click.

That's caused by the objective lens system focal length tolerances.

[tangolima]

Originally Posted by Bart B.

I disagree.

Which part?

-TL

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[Bart B.]

Originally Posted by tangolima

Which part?

-TL

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A milliradian is an SI derived unit for angular measurement which is defined as a thousandth of a radian (0.001 radian).

[JustJake]

Mil reticle with moa clicks is signature of cheap scope. Better scope has 1/10 mil clicks.

Correct.

Mil/Mil = a Mil reticle with elevation/windage turrets calibrated in Mil clicks, not MOA clicks.

It’s 2022 people.

Mil/MOA is sooo 1990s.

[bamaranger]

All this buzz about Mils and dots... oh my!

The OP's generic question leaves room for a broad range of response, and we've certainly gone there. It would be nice to know what type of rifle and sight system we are trying to discuss, and it's intended use. Such details guide responses and keep the thread from wandering.

There are many folks who zero their rifles "on" at 100 yds and hunt/shoot effectively, typically not shooting past that distance, as terrain and cover limit shot opportunities. If circumstances indicate that shots further than 100 will occur more frequently, a 2-3" high zero will maximize the rifles trajectory and allow holding "on" for deer size targets out to 250 yrs or so. Before twirly scopes and the fascination with sniping and long range shooting at big game, this was common practice.

To effectively hold high or vary a sight picture to hit on past established "on" zero, one must know that their rifle/load does in fact perform in that manner, or minimally , is producing the velocities claimed, with that specific projectile. A RN will not exhibit the same trajectory at distance as tipped BT by way of extreme example. Does the rifle in fact generate 2650 fps (example) at the muzzle, or is that relying on a published figure. My chronograph proves factory figures and many of my loads come far short of printed data. Result...slower, lower loads.

Even when drop and holdover can be accurately d determined, the issues of accurate range estimation and target ID are significant at distance. And any distance shooter will state foremost that WIND is their biggest concern.

Finally, don't rely solely on a short range 25-30 yd zero to predict down range performance. I realize that many do not have access to all but short range opportunities. But at first chance verify at distance. Reversing the procees, zeroing at distance, then shooting a 25 yd target, will allow a short range verification afield should trouble arise.

[Bart B.]

For all the miliradian fans, if you think adjustable metallic sights should also adjust in milliradian clicks, what thread pitch, clicks per revolution and radius should be used?

For SMOA, the numbers are 40 tpi and 12 clicks giving 1/4 SMOA for a 30 inch radius because most USA bullseye target scoring rings are spaced in inches.

[tangolima]

Originally Posted by Bart B.

For all the miliradian fans, if you think adjustable metallic sights should also adjust in milliradian clicks, what thread pitch, clicks per revolution and radius should be used?



For SMOA, the numbers are 40 tpi and 12 clicks giving 1/4 SMOA for a 30 inch radius because most USA bullseye target scoring rings are spaced in inches.

Let's go metric, shall we?

30 inches is 762mm. 0.76mm in 762mm is 1 mil. M6 fine pitch will do. 10 clicks per turn like in a M16A3. 0.1mil a click.

-TL

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