Merits of a 75 Yard Zero (Initial Intersection)

[saddlerocker]

I did a search and surprisingly not one thread on a 75 yard zero. (I know its not technically a zero, but thats how im going to refer to it here)

It would seem a 75 yard zero would be a perfect balance between the popular 50 yard zero and 100 yard zero.

You would be about .8" low at 50, on at 75, .5" high at 110, back on at 150, then increasingly lower from then on. (from molon's charts)

It would require no hold overs or unders from 50-175 yards and only be at a max 1" high or low. Barely noticeable and more than good enough to hit center mass.

I understand if your shooting for precision you would want to be exact, but for a battle zero this seems very simple to me.

Am I missing something obvious? I am by no means an expert.

[Belmont31R]

With a 50 yard zero you would be within a 4MOA Aimpoint dot from just past CQB to 250 yards depending on load on and offset over bore. At 250 yards a 4MOA dot would be 10".

[Jwalker]

For 30 years I used something similar to that on my scoped hunting rifles: one inch high at 100 yards, on at 165, one inch low at 200, and since the vast majority of my deer were inside that range it was hugely better than having to use a big hold-under on the most common, shorter, shots. That also left me an easy to remember five inches low at 250 and 10 inches low at 300, for shots that were relatively uncommon (to me, at least).

For an AR, though, it may not be the best for me. First, I expect I'll be using a red dot sight instead of a scope, and I won't be shooting much at 200 yards-plus. Second, one of the benefits of the Desanto 50-yard/200-yard zero is that a 25-yard initial cross of line of sight allows me to use the standard iron sight cam for other ranges as marked on the sight. Sight at a different range and the standard iron sight markings won't work.

[Failure2Stop]

I don't know where this whole, "You cant have a 'zero' at 'X' range" came from.
A 'zero' is simply a reference to sights (point of aim), point of impact with a specific cartridge, and distance. In fact, point of aim (POA) and point of impact (POI) do not even have to be the same. For example, one can zero at 25 yards by aiming at a given point and adjusting POI to be 1.5 inches low. The gun is therefore zeroed 1.5" low at 25 yards (with whatever ammo is used). This zero should give the shooter adequate hits at 200 yards with M193, however the shooter won't know that for certain until they actually shoot at 200 yards and adjust the POI as necessary. However, once they do that, they will have a 200 yard zero with POA being POI.

It is further compounded by environmental, equipment, and user variables. What was a 500 meter POA/POI zero at sea level in 95 degree heat with 77gr Mk262 will not be the same at 3,500 ft with (-)5 degree temperatures shooting M855 while wearing appropriate clothing

A zero is simply knowing exactly where the POI will be at a given range through the proof of actual shooting in conditions similar to those in use.

One can have multiple zeroes, but it's dependant on the sighting system. Adjustable sights (that are consistent accross the adjustment range) can be shifted from a baseline setting to correspond with settings from previous shooting experience. Therefore the sight may have a 200, 300, and 500 yard zero, for example.
Or, the shooter might have a reticle with multiple points in view which the user can then apply to ensure known POI at different distances. The BDC in many optics is an example of this, as are Mil-Dots.

So, you can zero at any distance you please, but the only distances at which you can claim a "zero" are those that you have actually shot to establish the POI/POA relationship. You might be able to guess where a shot will fall at a previously un-shot at distance with a ballistic calculator (as is necessary with practical precision marksmanship), but it is not nearly as reliable as known, real, data, and is not the same thing as a "zero".

Anyway:
75 yard zero?
I see nothing that it does that is distinctly better than the two prevalent zeroes, makes adjusting for distance more complicated than it needs to be, and will be in conflict with baseline zeroes for optics that are designed to work from a 100 meter baseline.

[trinydex]

i think the semantics battle lies in zero vs. initial intersection.

some find it semantically inaccurate to call an initial intersection a zero as the zero, to them, is defined as the final intersection.

just to clarify, i don't care and i don't want this thread to become an argument about that.

[Failure2Stop]

i think the semantics battle lies in zero vs. initial intersection.

some find it semantically inaccurate to call an initial intersection a zero as the zero, to them, is defined as the final intersection.

just to clarify, i don't care and i don't want this thread to become an argument about that.

Believe me, I understand their argument.
The comment was not directed at you, and while you might not want it to pop up, when you bring it up and make your own comments about it being impossible to zero at the near intersection or initial point, you're going to bring in these type of comments. It's like saying, "I know the moon is made of cheese, but what kind of cherries do cats like best?"

[Alaskapopo]

I did a search and surprisingly not one thread on a 75 yard zero. (I know its not technically a zero, but thats how im going to refer to it here)

It would seem a 75 yard zero would be a perfect balance between the popular 50 yard zero and 100 yard zero.

You would be about .8" low at 50, on at 75, .5" high at 110, back on at 150, then increasingly lower from then on. (from molon's charts)

It would require no hold overs or unders from 50-175 yards and only be at a max 1" high or low. Barely noticeable and more than good enough to hit center mass.

I understand if your shooting for precision you would want to be exact, but for a battle zero this seems very simple to me.

Am I missing something obvious? I am by no means an expert.

50 yard zero is better as its plus or minus 2.5 inches out to 250 yards which is good enough.
Pat

[ST911]

Critical variable to consider in determining what zero to use:

At a given distance, can the shooter deliver rounds to the target with sufficient accuracy and consistency to reasonably ascertain what POI the sights are adjusted to?

Most shooters will shoot well enough at 50yds to get a decent zero, given a reasonable grasp of the fundamentals of accuracy. The 75 and 100yd line will be a challenge for many. Beyond that, verifying the crossover/true zero at distance can often be an exercise in simply creating brass cases.

[Failure2Stop]

Another thing people forget about is adjusting sights.
It isn't impossible to do some simple math to figure out adjustments, but it's a lot easier at 50 or 100.

Really, there just isn't much going for it over the more standard zeroing distances.

[saddlerocker]

Well my thoughts were that there would be no adjusting

With a 50 yard zero you would be almost 2" high at 125, need to hold under
With a 100 yard zero you would be about 1" low at 50, which is acceptable, but it drops more at the longer distances

With a 75 yard you would be .8 low at 50 and 1" high at 125
Basically always within 1" with no adjustments until your past 200 yards

It seems the best of both worlds. Were not shooting for sub-MOA groups, it just puts you within 1" with no thinking, no hold overs/unders until past 200 yards

Picture a line in between the 50 and 100 yard zeros (!This Chart is From MOLON's Posts!)
This is for M193 out of a 16" Barrel
http://i51.tinypic.com/okqrz9.jpg

[glocktogo]

I use the 50 yard zero because it works for me. Others use a 100yd and you can certainly use a 75yd if that's what will work best for your usage parameters. I think mastering mechanical offset for close in precision shots is much more critical to self-defense work for civilian and LE users, than whether you hit 1 or 2 inches above or below point of aim in excess of 35 yards.

Apologies to the semantically obsessed for using "zero" in place of initial intersection. :D

[Failure2Stop]

This is what happens when people spend more time staring at charts than shooting.
If you want a 75 (or 100, or 50, or 200, or 17.5) yard zero for whatever reason, go get out on the range and do it and report back in 5,000 rounds after doing everything from 1 to 300 meters, a few competitions, and compare it to other zeroing methods and report back with what you did, how you did, and how well it worked compared to other zeroes.

I used to look down on the 100 meter zero for anything other than baseline for precision optics. After testing it out for a few thousand rounds under the conditions above I came to realize the utility and appreciate the zero. A 200 yard/meter zero is also decent, in fact I prefer it for irons, but I don't want to have different zeroes to have to think about when transitioning to an emergency sighting system.

To quote Rob_S:
Go shoot the gun.

It will provide much more useful data than arguing about it with strangers on the net.

[saddlerocker]

My rifle is zeroed for this "75/185 yard" zero, the problem is that I only shoot Irons and im not the best shot, so seeing a .5" drop or rise is basically impossible.

My range has 50/100/200 yard target stands, I also set up my own targets at 75 yards to be sure.
I have confirmed it for the most part, but I would need a led sled and magnified optic to really see the effect.

Im not trying to persuade anyone to use it, I was just surprised that when I searched for it there was no mention of a 75 yard zero, and was wondering if I was missing something.

It seems best for my purposes, so ill continue to use it and hopefully down the road I can get some better data on it.

[rob_s]

What you will find is that most people talking about a thing actually have little to no experience with said thing. That used to be less true here but not so much of late.

If a 75-yard initial intersection, as you rightly called it, works for you and you know what your true zero is and have fine-tuned the zero at that distance then motor on. Adjusting my usual instructions for the 50/200 for your model:

get on paper at 25 yards
get POI=POA at 75 yards
get zero at 185 yards (using your number, no idea if this is right)
check at 75 yards
verify hold over/under at various distances



I have come to prefer a 100-yard zero for a few reasons, not the least of which is that it has an initial intersection that is close enough to true zero, and because the POI is always either at or below POA. Furthermore, I posit that the #1 reason most people choose the 50 and then insist that it is, in fact, a zero is because it is the shortest distance at which they can zero that they find to be tactically acceptable among their peers or online. Not all, but most.

[Jwalker]

Failure2Stop: This is what happens when people spend more time staring at charts than shooting. That might have been a little harsh, I think. He's looking at something new and has a reason for his thinking. He asked a question and explained why. To have that dismissed as useless is mistaken.

[Alaskapopo]

That might have been a little harsh, I think. He's looking at something new and has a reason for his thinking. He asked a question and explained why. To have that dismissed as useless is mistaken.

A little more time shooting and he would know that he is splitting hairs. There is no reason to reinvent the wheel the 50/200 yard zero works well. What really matters is that you know how to shoot your rifle and know where it hits at various ranges. Charts help but you have to go out there and shoot.
Pat

[Jwalker]

Pat,

Splitting hairs? We're not on a "General Firearms" forum, we're on an M4 forum that also drills down pretty far into split hairs - optics, zeroes, etc. That's pretty much the definition of splitting hairs. Leave out split hairs and the forums have nothing to do, or, worse, act like arfcom and lock any thread in which there are criticisms of (1) advertisers or (2) mods, or (3) have some FAQ somewhere that no one can find.

I agree that the standard 50-yard/200-meter zero is a good one, and said so in the third post from the top. I objected not to the answer but the dismissive attitude I saw. Do we now think courtesy is a weakness that must be avoided? I hope not. FWIW, it's not the first discourteous response I've seen lately; it's just that I expect more from a mod.

[Alaskapopo]

Pat,

Splitting hairs? We're not on a "General Firearms" forum, we're on an M4 forum that also drills down pretty far into split hairs - optics, zeroes, etc. That's pretty much the definition of splitting hairs. Leave out split hairs and the forums have nothing to do, or, worse, act like arfcom and lock any thread in which there are criticisms of (1) advertisers or (2) mods, or (3) have some FAQ somewhere that no one can find.

I agree that the standard 25 yard/200 meter zero is a good one, and said so in the third post from the top. I objected not to the answer but the dismissive attitude I saw. Do we now think courtesy is a weakness that must be avoided? I hope not. FWIW, it's not the first discourteous response I've seen lately; it's just that I expect more from a mod.

You are a bit confused on this. Its the 50yard 200 (give or take depending on ammo) zero.
The 25 yard zero is actually more like 340 yards on the outside.
Pat

[Jwalker]

Thanks, I did know that. "Writo," in stead of "typo."