POI Using Iron Sights at Various Distances

[Chief TC]

You know it does get hard to fully explain and talk about this topic. I will try to clarify best I can.

I posed the question in regards to how iron sights are designed. I should have stated this upfront. Most of us have a good understanding of ballistics, so this is not about adjusting sights to a specific MOA to be on target at a specific distance. Ballistics calculators and scopes and vernier sights easily help us achieve that goal. I shoot BPCR and so most people use vernier sights if they use iron sights.

I was thinking and wondering if iron sights on rifles followed some sort of specific MOA design. A manufacturer can design the sights any way they want so the bullet impacts the target a specific way based on the cartridge ballistics. So, for example, let's take Bronco's M1A. He states his POI increases per MOA as he increases the distance. 3" at 100, 6" at 200, etc. So this means the manufacturer designed the sight setting to perform in this manner. My real world range experience is different and depends on which rifle. My general experience is that my rifles tend to shoot the same measurement of POI from POA at various distances.

So thinking about this from a military training standpoint, if a rifle's sight design was like that of Bronco's M1A, then you have to teach people to shoot much lower at longer distances, whereas, if the sights were designed to always have the same POI, then your POA does not change. So all that to say, how are most rifle sights designed?

 

[DustyRusty]

I posed the question in regards to how iron sights are designed.

OK. Rifle sights.

Different rifle designs do it differently. Battle rifles are graduated in yards or meters, and some add click adjustments that are graduated in MOA like the M1, M1a, M16, AR-15, O3 Springfield windage.

The graduations for yards or meters help you correctly raise or lower the sights as range to target increase or decreases. It is compensation for bullet drop.

The clicks make it easy to make known changes to your sights by feeling the number of clicks. Clicks are usually in MOA. More detail on request.

 

[Bronco72]

I have the sight setting on my M1A memorized, so many clicks up from from bottom to hit center of bullseye with 6 o'clock POA.. I do not remember how that corresponded to to the yardage markings on the rear sight I think I only used the sight setting as a starting point to fine tune it to the clicks up that suited me and then wrote them down for future use. ! 12 clicks up from bottomed out was for 200 yds. 15 up for 300 and 23 up for 600 on the NRA full distance bulleyes I always went back to zero when changing distances and re-counted up. I also must of not fully understood you initial question. I plead an inordinately thick skull.
Sorry about that
John
Edit
I also appreciate how this discussion went cordially, not like other conservations that go sideways.

 

[Chief TC]

No worries, John. Definitely is tough sometimes to clearly convey a topic like this. Thanks for the great discussion. I still learned some stuff.

 

[Chief TC]

OK. Rifle sights.

Different rifle designs do it differently. Battle rifles are graduated in yards or meters, and some add click adjustments that are graduated in MOA like the M1, M1a, M16, AR-15, O3 Springfield windage.

The graduations for yards or meters help you correctly raise or lower the sights as range to target increase or decreases. It is compensation for bullet drop.

The clicks make it easy to make known changes to your sights by feeling the number of clicks. Clicks are usually in MOA. More detail on request.




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Right, all these sights are designed and operate differently. You get the most flexibility with a 1 click per MOA rear aperture sight like on the M1. You can keep your POI relatively that same from your POA. With sights that have specific distance settings like the 1903A3, that is where I think it get more variable and complicated to determine POI at various distances.

 

[NZ308]

Actually this is the first I’ve heard of lights up, sights up. I do account for lighting conditions but mostly in regards to the aperture size and low light. I’m trying to think about mirage more.

The light up sight up accounts for the increased light flare reflecting on the blade tip, if you are running front rings then not needed. Be aware if you adjust your rear sight elevation then the rear aperture size then they may cancel each other out.

As previously stated that if the aiming mark scales the same at each range in MOA then the 6 o'clock hold is a constant offset of the sight setting, be aware if you go to another range complex from your home range this may not hold true. Your range may be 'true' or have a constant error in the distance of the firing points which allows the offset to follow. Other complexes may have a slightly different offset due to distance or light conditions encountered - the worst one is when the distance steps are random slightly shorter and/or longer for each firing point.
Best advise is to have your home range nominal elevation recorded with offset recorded as your rifles zero and come up settings. At each new range you go to ask a local what their come up is for each range is and compare (assuming simular setup or if they have been to your range the differences found between the two) with you nominal elevation and once finished the range record your fired elevation for next time.

Record every shoot: equipment and ammunition details, time and date, complex and distance fired with which target engaged, environmental conditions like temperature, weather and light conditions. Used to have a range that the 900 yard line went from 20 short to 10 long and if you did not know this the elevation changes needed caused a lot of confusion if you went from one end to the other.

The idea is to develop knowledge and compare results over time - is there any consistency in settings distance X elevation is between these values with true being: value, or in these conditions you need to do some change to settings, even to load changes needed for temperature or elevation - ie New Mexico vs coastal ranges.

 

[AJC1]

If your POA is a six o'clock hold at 100 yds and the POI is 3" higher; the POI is 3 minutes higher than the POA. Therefore at 200 yds 1 minute = 2" so the POI would be 6" higher than the POA..... 600 yds the POI is 18" higher than the POA. So on and so on.

What makes that worse is bullet drop is more at each consecutive range... having known settings on competition day sure helps. For short range steel "357" we don't change them. 6 o'clock hold on chickens, belly of pigs, dead on for turkeys and top of the back on rams. That works perfect for junior but most guys dial.

 

[NZ308]

You know it does get hard to fully explain and talk about this topic. I will try to clarify best I can.

I posed the question in regards to how iron sights are designed. I should have stated this upfront. Most of us have a good understanding of ballistics, so this is not about adjusting sights to a specific MOA to be on target at a specific distance. Ballistics calculators and scopes and vernier sights easily help us achieve that goal. I shoot BPCR and so most people use vernier sights if they use iron sights.

I was thinking and wondering if iron sights on rifles followed some sort of specific MOA design. A manufacturer can design the sights any way they want so the bullet impacts the target a specific way based on the cartridge ballistics. So, for example, let's take Bronco's M1A. He states his POI increases per MOA as he increases the distance. 3" at 100, 6" at 200, etc. So this means the manufacturer designed the sight setting to perform in this manner. My real world range experience is different and depends on which rifle. My general experience is that my rifles tend to shoot the same measurement of POI from POA at various distances.

So thinking about this from a military training standpoint, if a rifle's sight design was like that of Bronco's M1A, then you have to teach people to shoot much lower at longer distances, whereas, if the sights were designed to always have the same POI, then your POA does not change. So all that to say, how are most rifle sights designed?

Bronco's math is correct with the angular change of impact of a 1 Minute of Angle being 3"@100 and 6"@200 from PoA seeing as the sight adjustment was designed in MoA. The sights offset needed to hit center of a target can be a constant MoA for scaled targets as the target is designed to have the same angular center to edge value.
A constant target size used at multiple distances with the same PoA will after bullet drop compensation for change of distance will need a change of offset to hit center as the angular offset from center to edge has changed.
So in the example above if a 1MoA offset to hit center of a 6" target at 100 was needed then at 200 the same 6" target will need 0.5MoA offset. If on the otherhand the target changes to 12" then it stays 1MoA - to hold one variable constant then the other has to change in the opposite proportion. The M1A sight has a range scale based on center hold being applied (used one until we had to surrender them)

The Military train Center of Mass hold so PoA and PoI should be co-located and with Battle Zero have little to no issue with needling to workout hold offsets beyond either from muzzle to some distance hold center if longer hold higher for area engagement. The target disciplines on the other hand shoot for score and add mathematical complexity to the equation.
We add scaled targets or fixed sized targets, we add different sight adjustments MoA/mRAD/fixed, different shapes and scoring zones with different ways to engage with center or bottom/top holds.
Your real world experience is likely on scaled targets so PoI to PoA holds true or you have corrected the dope for drop to range without understanding it was being done to also change the offset applied so PoI relativeto PoA stays the same.

Try doing the Swiss Military Qualifications using a Palma sighted rifle - the round dot is easy but the silhouette face comes fun if you use the normal round dot technique for the distance - hint change the ring size to use the entire frame for aiming seeing as both have center of target for max score zone. Same distance but different target parameters need different tactics for engagement if you can make setup changes or use one for both but you have to develop the knowledge as to which you apply.

 

[Chief TC]

Bronco's math is correct with the angular change of impact of a 1 Minute of Angle being 3"@100 and 6"@200 from PoA seeing as the sight adjustment was designed in MoA. The sights offset needed to hit center of a target can be a constant MoA for scaled targets as the target is designed to have the same angular center to edge value.
A constant target size used at multiple distances with the same PoA will after bullet drop compensation for change of distance will need a change of offset to hit center as the angular offset from center to edge has changed.
So in the example above if a 1MoA offset to hit center of a 6" target at 100 was needed then at 200 the same 6" target will need 0.5MoA offset. If on the otherhand the target changes to 12" then it stays 1MoA - to hold one variable constant then the other has to change in the opposite proportion. The M1A sight has a range scale based on center hold being applied (used one until we had to surrender them)

The Military train Center of Mass hold so PoA and PoI should be co-located and with Battle Zero have little to no issue with needling to workout hold offsets beyond either from muzzle to some distance hold center if longer hold higher for area engagement. The target disciplines on the other hand shoot for score and add mathematical complexity to the equation.
We add scaled targets or fixed sized targets, we add different sight adjustments MoA/mRAD/fixed, different shapes and scoring zones with different ways to engage with center or bottom/top holds.
Your real world experience is likely on scaled targets so PoI to PoA holds true or you have corrected the dope for drop to range without understanding it was being done to also change the offset applied so PoI relativeto PoA stays the same.

Try doing the Swiss Military Qualifications using a Palma sighted rifle - the round dot is easy but the silhouette face comes fun if you use the normal round dot technique for the distance - hint change the ring size to use the entire frame for aiming seeing as both have center of target for max score zone. Same distance but different target parameters need different tactics for engagement if you can make setup changes or use one for both but you have to develop the knowledge as to which you apply.

Great explanation - many thanks!

 

[NZ308]

Just be aware with MoA change in value is in real world 1" per hundred yards so 1 at 100 and 10 at 1000.

 

[Chief TC]

Just be aware with MoA change in value is in real world 1" per hundred yards so 1 at 100 and 10 at 1000.

Oh yes, I am well aware of how that works. Can't use a vernier sight without understanding that fundamental fact.