AR-15 Zeros and Trajectories

[The Annoyed Man]

Not to necro again, but I've bookmarked this thread for the information on the Santoze modified 50yard/200meter zero. I do have a question for Molon if he cares to answer it:

Preface:
I have a Trijicon TA31F (4x32, red chevron) for my primary carbine optic, and I am not certain that I want to use the reticle any differently than its original intent with a 100 yard/meter zero, because the subtensions on the bullet drop compensator are regulated for that zero.

Question:
With that in mind, is it there anything tactically unsound about using the 50 yard zero for my iron sights (should the scope become damaged), while maintaining the 100 yard zero for the 4X optic? Alternatively, has anyone ever worked out what the subtensions on the Trijicon TA31F's bullet drop compensator would work out to with the scope zeroed at 50 yards? I realize that the ballistics would be unchanged for the cartridge;, but for instance, what would the 400meter mark on the BDC work out to with a 50 yard zero?

I'm an old poop with the older Mark 60+ eyeballs, and I can't really see a target that clearly beyond about 50 yards without magnification (and/or glasses). This particular carbine is a both a general purpose/hunting carbine (Texas hogs and whitetail) as well as my SHTF weapon. God willing and the creek don't rise, I'll never need iron sights. I really like the idea of the 50 yard zero and its flatter shooting trajectory out to real-life distances. I'm just wondering if it is at all worth it to do that with the Trijicon.

[M&P15T]

Oh I know man. This thread is top notch! Some guys just need the simple part explained with crayons and a white board. I have had to explain the fact that bullets do not generate "lift" and flight like the foil on wings to too many buddies. Figured some guys would "get it" with the explanation.

I have heard a few people talk about certain bullets/cartridges that "rise" when they leave the barrel. Even when I was new to rifle shooting, I knew that was against the laws of physics. Still, plenty of people operate under that confusion.

[The Annoyed Man]

I have heard a few people talk about certain bullets/cartridges that "rise" when they leave the barrel. Even when I was new to rifle shooting, I knew that was against the laws of physics. Still, plenty of people operate under that confusion.

Apparently, they have not ever heard of parallel and converging axes, nor of gravity.

[markm]

Apparently, they have not ever heard of parallel and converging axes, nor of gravity.

That's a bunch of liberal nonsense.

[M&P15T]

That's a bunch of liberal nonsense.

Thanks for the morning laugh.

Having read this thread and others, it seems no particular zero is perfect, or better than another. it's all about choosing a specific zero, sticking with it, and knowing your dope at different distances based on your chosen zero.

Still, I think one does need to consider what is the most likely scenario they might have to use their AR to defend themselves, and zero for it.

This thread makes me more anxious to ditch my aimpoint clone (lower 1/3rd) and get back to an Eotech (co-witness) next month. I like having concrete ballistic data points that are supported by my chosen optic, rather than screwed up by it.

Has any ever tested to see what the POA/POI differences are between lower 1/3rd and absolute co-witness with different distance zeros? I can't imagine it would be much.

[markm]

Thanks for the morning laugh.

Having read this thread and others, it seems no particular zero is perfect, or better than another. it's all about choosing a specific zero, sticking with it, and knowing your dope at different distances based on your chosen zero.

That's what we do. Just stick to a 100 yard zero and when we jump from gun to gun we already have an idea of the come up for that caliber as we work out to longer ranges.

Has any ever tested to see what the POA/POI differences are between lower 1/3rd and absolute co-witness with different distance zeros? I can't imagine it would be much.

You can plug in sight over bore variances in to trajectory programs. I mess with the program before and sight height was very negligible.

[M&P15T]

You can plug in sight over bore variances in to trajectory programs. I mess with the program before and sight height was very negligible.

I figured as much. Although logic would dictate that the POA/POI differences are magnified at longer distances.....right? Or.....no.....the difference would remain constant? No....no....a slight difference at, say, 25 yards would be magnified at 200 or 300 yards?

Coffee....where's my coffee......muh brain ain't workin'.

[Failure2Stop]

I figured as much. Although logic would dictate that the POA/POI differences are magnified at longer distances.....right? Or.....no.....the difference would remain constant? No....no....a slight difference at, say, 25 yards would be magnified at 200 or 300 yards?

Coffee....where's my coffee......muh brain ain't workin'.

Line of sight difference between absolute and lower 1/3 cowitness makes zero practical difference.

[Cincinnatus]

I had a commercial carry handle laying around, so...
In order to "adjust" a commercial-height carry handle sight to mil-spec height, and then be able to back it down for the 100 yard zero, I am doing this:
I loosened the detent screw so as to adjust the elevation wheel separately, just like when adjusting for RBZ, but instead of dialing the drum down, I dialed it up the .40 to where it is equal to the mil-spec height, then re-tightened the screw. Now my starting point is the 6/3 point (with number dial labeling it thus), just like a mil-spec carry handle. Now I dial it counter-clockwise 8 clicks (removable carry-handles are supposed to receive double the clicks of an A2 sight): this should now be the point for my 100 yard zero, correct?
The only downside (besides potential quality problems with a commercial carry handle) that I can think of so far, is that now my maximum dial-in range for the sight is now about 575 yards instead of 600 or beyond, as it is with a mil-spec carry handle.
Does this "fix" work the way I am thinking it does, or are my computations way off?

[Doc Safari]

I have recently become a real fan of the RIBZ. 6/3 -4 clicks at 50 with the detachable carry handle. I would love to see a chart or table to simply list in "number of clicks" clockwise from 6/3 -4 (or from just 6/3) to use for each subsequent elevation setting. Not that I'll be doing much shooting at 400 yards, for example, but some of the charts and graphs can be somewhat mind-boggling at the same time they are informative.