36 yard zero - Red dot

[Cincinnatus15]

Is anyone using the 36 yard BZO with a red dot, 2 MOA type?

[Koshinn]

I think most people here at least use the 100m zero because this (https://www.m4carbine.net/showthread.php?107572-Zen-of-the-100-Meter-Zero).

Why do you ask?

[HD1911]

I'm personally a fan of a 50m Zero on a RDS equipped Rifle/Carbine. Gets me to 200y with no holdover and hits 300y holding Top Edge of a 12" Plate, yet rises no more than 1.7" above Line of Sight... this is with M193/M855/Mk262

[Failure2Stop]

Is anyone using the 36 yard BZO with a red dot, 2 MOA type?

Nope.

Highly recommend a 50, 100, or 200 meter/yard zero.

[Campbell]

I'm personally a fan of a 50m Zero on a RDS equipped Rifle/Carbine. Gets me to 200y with no holdover and hits 300y holding Top Edge of a 12" Plate, yet rises no more than 1.7" above Line of Sight... this is with M193/M855/Mk262

This, for these reasons...for my shooting it just works.

[samuse]

I'm personally a fan of a 50m Zero on a RDS equipped Rifle/Carbine. Gets me to 200y with no holdover and hits 300y holding Top Edge of a 12" Plate, yet rises no more than 1.7" above Line of Sight... this is with M193/M855/Mk262


Nope.

Highly recommend a 50, 100, or 200 meter/yard zero.


These. A 200M zero is very close to the same as a 50 yard zero.

I have NEVER had a close intersection zero line up perfectly with the far intersection.

I zero at 200, confirm at 50. I call it a 200 yard zero.

[ABNAK]

50yd IBSZ is my preference for the reasons stated above.

[Molon]

AR-15 Zeros and Trajectories

The 100 yard zero with a .223/5.56mm AR-15 carbine is a unique trajectory in that the bullet just “kisses” the line of sight at 100 yards and rides along it for approximately 10 yards before dropping back down below the line of sight. (Technically, the bullet does travel above the line of sight, but by only 0.010”; a fraction of the diameter of the bullet itself.)



http://www.box.net/shared/static/l5orbycc2z.jpg



For all other zeroing schemes, there are going to be two points were the bullet crosses the line of sight; the near-zero and the far-zero. For the near-zero, the bullet will cross the line of sight while traveling upwards towards the apogee or “maximum ordinate,” its highest point of travel. For the far-zero, the bullet will cross the line of sight while traveling downward from the maximum ordinate.

Now, when assigning a name to a particular zeroing scheme, it would be helpful if that name gave descriptive information about that particular zero; that is, the name should give us information about the trajectory and how it is unique and differs from other trajectories.

As a point of reference, the Santose Improved Battlesight Zero is often referred to as a 50/200 yard zero, however this is incorrect. It is actually a 50 yard/200 meter zeroing scheme; and this is only with a very few particular combinations of bullet weight, barrel length/muzzle velocity and height of sights above the bore. As an example, a 20” barreled AR-15 A2 firing 62 grain M855 will not match the 50 yard/200 meter IBZ. Neither will a 16" barreled RECCE firing 77 grain MK262, nor a 14.5” barreled M4 carbine firing the 70 grain 5.56mm Optimized "Brown Tip" load. The same concept applies when people refer to a 50/225 yard zero. Only a very few specific combinations of bullet weight, barrel length/muzzle velocity and height of sights above the bore will match that description.

What this is all leading up to is this; except for a very few specific combinations of bullet weight, barrel length/muzzle velocity and height of sights above the bore, a 50 yard zero is a different zero than a 200 yard zero. For a 200 yard zero, we know that this trajectory will produce a far-zero in which the bullet will cross the line of sight at 200 yards in its downward travel from the maximum ordinate. (It is physically impossible to produce a 200 yard near-zero with any of the commonly available loads and barrels lengths used in .223/5.56mm AR-15s.) Other than for a very few specific combinations of bullet weight, barrel length/muzzle velocity and height of sights above the bore, the near-zero of the 200 yard zero will not be at 50 yards.

Conversely, a 50 yard zero tells us that this trajectory will have a near-zero in which the bullet crosses the line of sight at a distance of 50 yards in its upward travel to the maximum ordinate. For those who think that a zeroing scheme must be named after its far-zero, it is physically impossible to produce a far-zero of 50 yards with any of the commonly used loads and barrel lengths in .223/5.56mm AR-15s. The 50 yard zero can only be the near-zero.

Other than for a very few specific combinations of bullet weight, barrel length/muzzle velocity and height of sights above the bore, the far-zero of the 50 yard zero will not be at 200 yards; and for all practical purposes it matters not one bit. Whether the bullet crosses the line of sight for the second time (far-zero) at 189 yards, 200 yards or 215 yards will not make the slightest bit of difference in the practical application of the AR-15 as a defensive weapon. In each case we will be holding the same POA (beyond CQB distances) and know that we will be hitting within approximately 2 inches above or below that POA out to 200 yards (or farther depending upon barrel length and load.) You should have an idea what your actual far-zero is when using a 50 yard zero and confirm such at distance when possible, but again it’s most likely not going to be a 200 yard far-zero and again it does not need to be.

Choose your zeroing scheme based on the pertinent facts; not nonsense about “shooting through a cone.” When shooting at human targets, in the grand scheme of things there isn’t going to be any practical difference between a point of impact that has a negative deviation from the point of aim, (e.g. the bullet strikes 1.5” below the point of aim) and a point of impact that has an equal positive deviation from the point of aim (e.g. the bullet strikes 1.5” above the point of aim.) In other words, the absolute value of the point of impact from the point of aim (how far the point of impact deviates from the point of aim, regardless of whether it is a positive or negative deviation) is what we need to be concerned about. Therefore, one of the main points to consider when choosing a battle-sight-zero is this: What zeroing scheme produces the smallest absolute values for the deviations of the points of impact from the point of aim, over the distance that we reasonably expect to engage a human target in our intended usage?

The chart below illustrates the above concept. The chart compares the absolute values of the deviations of the points of impact from the point of aim (0.0 inches on the graph being the point of aim/line of sight) for a 50-yard-zero and a 100-yard-zero, using Hornady 5.56 TAP T2 ammunition.


http://www.box.com/shared/static/dff892e7179fa7e265a7.jpg


As you can see in the graph above, from the muzzle (0 yards) to approximately 62 yards, the 50-yard-zero has a slight advantage over the 100-yard-zero. Between the distances of 62 yards and 165 yards, the 100-yard-zero has the advantage. From the distance of 165 yards out to the 250 yards shown in the graph, the 50-yard-zero has a distinct advantage over the 100-yard-zero. Choose your zeroing scheme based on the pertinent facts.




Some reference material. Except where noted, all barrel lengths are 20 inches.


http://www.box.net/shared/static/xuhqpttxnv.jpg
Courtesy of zrxc77





M855 25 yard zero

http://www.box.net/shared/static/cednvi8d7o.jpg



M855 25 meter zero

http://www.box.net/shared/static/f2aede6t0d.jpg




M855 25 meter zero versus 300 meter zero

http://www.box.net/shared/static/mni5s9tkr6.jpg




M855 36 yard vs 100 yard zero

http://www.box.net/shared/static/3v8tyg2uu1.jpg




M855 and M193 25 meter zero

http://www.box.net/shared/static/pg9s5r0xl5.jpg




M855 and M193 50 yard zero from 16” barrel

http://www.box.net/shared/static/8xved8kfrm.jpg



M193 25 meter, 50 yard and 100 yard zeros from 16" barrel

http://www.box.net/shared/static/c0dvpkdudy.jpg




100 yard zero

http://www.box.net/shared/static/gh6i3193lr.jpg




25 meter vs 50 yard zero, M855 from 16” barrel

http://www.box.net/shared/static/kek3hftq3o.jpg




M855 300 meter zero

http://www.box.net/shared/static/yleso2f74i.jpg




M855 200 meter vs 300 meter zeros

http://www.box.net/shared/static/x8ekjyj6av.jpg


M855 36 yard vs 50 yard zeros

http://www.box.net/shared/static/s02id508i8.jpg




. . .

[tom12.7]

I generally recommend something similar to the 50/200 zero for most carbines, but some adjustment to that can be common with the different variables involved and user needs. Generally, I tend to recommend a zero that fits the users required accuracy requirements with a distance from the muzzle, or specified otherwise to a maximum distance, that fit individual needs with intersection points in between. In those cases, a number like the OP's 36 yards is not unheard of, but it really depends on the actual situation is. 36 yards is not my choice for anything right now, that doesn't mean that it isn't in the future, it's just not likely.

[PatrioticDisorder]

For a red dot I zero at 50 yards and shoot at 100 yards to ensure windage is staying true and if it's off I'll modify windage as needed. I zero scopes in at 100 yards.

[Cincinnatus15]

Wow thank you guys so much, I didn't expect to get this kind of response. To answer some of your questions as to why I asked about The 36 yard zero, this is what we used in the Marine Corps. I saw a Travis Haley video where he demonstrated the differences between the 25, 50, 100, 200, 300 yard zeros and it seemed to me that the 300 yard zero held a 5 inch group out to 300 yards. I'm currently using a 50/ 200 yards zero for my red dot and its worked out great. I just thought that I would ask to see if anyone is using the 300 yards zero because it seem to be the best demonstrated in the video. I guess I'll keep using the 50/200 yard zero, thanks again for all your responses gentleman.

Edit: when I talk about the 300 yard zero I'm referring to the 36/300 yards zero

[WaldoOneFive]

Wow thank you guys so much, I didn't expect to get this kind of response. To answer some of your questions as to why I asked about The 36 yard zero, this is what we used in the Marine Corps. I saw a Travis Haley video where he demonstrated the differences between the 25, 50, 100, 200, 300 yard zeros and it seemed to me that the 300 yard zero held a 5 inch group out to 300 yards. I'm currently using a 50/ 200 yards zero for my red dot and its worked out great. I just thought that I would ask to see if anyone is using the 300 yards zero because it seem to be the best demonstrated in the video. I guess I'll keep using the 50/200 yard zero, thanks again for all your responses gentleman.

Edit: when I talk about the 300 yard zero I'm referring to the 36/300 yards zero

I am surprised that no one else has chimed in favor for the 36/300yd Zero. After that zero comparison by Travis Haley in the Make Ready video, I looked into it further. I have been using the 50/200 for quite some time, but after reading Molon's posts on here and TOS a million times, and finally being able to truly TEST my duty ammo out of MY barrel length and got the real numbers I found that the 36/300 yard Zero was best for me personally.

Basically, I wanted the best "combat effective" zero from a 14.5 colt 1/7 barrel, using the Gold Dot #24448 64gr .223. After finding the velocity, the BC, etc etc, and punching ALL the numbers, OVER and OVER again on Strelok/Ballistic Calculator, and then shooting them at the ranges, I found that the 36yd zero had the "smallest" deviation (high/low). From 0 yards to roughly 285 you get a 5-6 inch group, and past 285 you get the drop off and would need to remember those hold overs. So again... for me, and my barrel, and ammo, this is the best in order to get the smallest "effective group" out to 300 yards... The other zeros had all wacky hold-overs and greater high/low deviations.

I hope this made sense to those who have read it..

[Molon]

I saw a Travis Haley video where he demonstrated the differences between the 25, 50, 100, 200, 300 yard zeros . . .



That video contains glaringly false information. While everyone is certainly entitled to their own opinion, they're not entitled to their own Laws of Physics.


....

[Molon]

I am surprised that no one else has chimed in favor for the 36/300yd Zero.



For starters, the 36/300 yards zero only applies to M855 being fired from a 20" NATO chambered barrel (or a 20" barrel with ammunition that has an identical BC and MV). Secondly, do you know what the most commonly missed targets are on the US Army 300 meter pop-up target qualification?








Basically, I wanted the best "combat effective" zero from a 14.5 colt 1/7 barrel, using the Gold Dot #24448 64gr .223. After finding the velocity, the BC, etc etc, and punching ALL the numbers, OVER and OVER again on Strelok/Ballistic Calculator, and then shooting them at the ranges, I found that the 36yd zero had the "smallest" deviation (high/low). From 0 yards to roughly 285 you get a 5-6 inch group, and past 285 you get the drop off and would need to remember those hold overs. So again... for me, and my barrel, and ammo, this is the best in order to get the smallest "effective group" out to 300 yards...



The trajectory that you have just described is physically impossible for the Speer 64 grain Gold Dot fired from the 14.5" Colt M4 barrel.

Using an average muzzle velocity that I obtained from chronographing three different lots of the Speer 64 grain Gold Dot from two different 14.5" Colt M4 barrels, the 64 grain Gold Dot will have a POI that is more than 3" higher than the POA at its apogee with a 36 yard zero. The 64 grain Gold Dot fired from a 14.5" Colt M4 barrel will have a POI that is more than 6" lower than the POA at 285 yards with a 36 yard zero. That is a vertical spread of more than 9" from 0 to 285 yards, and that is only if you, your barrel and your ammunition execute a perfect shot every single time.



https://app.box.com/shared/static/9v6omjnyuuzh1n3z5t0bd6lc8o49dst6.jpg




https://app.box.com/shared/static/1fib8hvegolvwgw6squjqauqnjli1920.jpg




.....

[T2C]

I think that you can only choose the correct zero when you have determined the muzzle velocity of the weapon/ammunition, ballistic coefficient of the projectile and the intended use of the weapon system. As a general rule, I like a 50M/200M zero for a lot of applications.

Molon brings up a very good point about ammunition selection.

[Renegade]

Is anyone using the 36 yard BZO with a red dot, 2 MOA type?

Most of my zeros are in the low 40s.

I battle sight each firearm based on actual POI, not calculators. Yes it is time consuming, but it is perfect. It of course varies with ammo, BBL Length, HOB.

[WaldoOneFive]

For starters, the 36/300 yards zero only applies to M855 being fired from a 20" NATO chambered barrel (or a 20" barrel with ammunition that has an identical BC and MV). Secondly, do you know what the most commonly missed targets are on the US Army 300 meter pop-up target qualification?







The trajectory that you have just described is physically impossible for the Speer 64 grain Gold Dot fired from the 14.5" Colt M4 barrel.

Using an average muzzle velocity that I obtained from chronographing three different lots of the Speer 64 grain Gold Dot from two different 14.5" Colt M4 barrels, the 64 grain Gold Dot will have a POI that is more than 3" higher than the POA at its apogee with a 36 yard zero. The 64 grain Gold Dot fired from a 14.5" Colt M4 barrel will have a POI that is more than 6" lower than the POA at 285 yards with a 36 yard zero. That is a vertical spread of more than 9" from 0 to 285 yards, and that is only if you, your barrel and your ammunition execute a perfect shot every single time.



https://app.box.com/shared/static/9v6omjnyuuzh1n3z5t0bd6lc8o49dst6.jpg




https://app.box.com/shared/static/1fib8hvegolvwgw6squjqauqnjli1920.jpg




.....


Sir, I truly thank you so much for your effort to pull my figures apart and prove/disprove them. I seriously need to look at the numbers I have been punching in here to see what I have been messing up so bad. I say the term " 36/300" but know that those aren't matching numbers except for 855 in a 20" barrel.

I am going to get those numbers and post them up because I would love to see what my failure was in doing the math.. I drool over your data all the time, and am blown away looking at your trajectory images using my setup as the test case. I appreciate your feedback, and will get my info asap. Thank you!

[WaldoOneFive]

Molon, this is what I am getting with the following Info:

Speer Gold Dot 24448 64gr out of 14.5 barrel:

Weight - 64 grains
B.C. - .267
Velocity - 2588


Zeroing Weather - 75 degrees F - 396ft above sea level - Pressure: 29.53 Hg

With that info, I get this:


Yards | Inches
5= 2.2
15= 1.4
25= .70
36= 0 - Zero
50= -.8 high
75= -2.0
100= -2.8
125= -3.2
150= -3.1
175= -2.6
200= -1.6
225= 0 - Crosses Zero
250= 2.1
275= 4.8
300= 8.1
325= 12.2

Does this look more accurate? Again, in my head, I basically just like that this zero gives me 3 inches high and low out to 260 yards. I misspoke earlier in my post, and even with this one, I am second guessing my work.

the whole point of my personal research was to have the "tightest" overall group (height-wise, up and down) from 0 yards to roughly 300+/-. Molon, with this combination of my setup, the 14.5 colt and the Speer 24448 rounds, is there, or do you recommend a better Zero to use that will yield a smaller overall spread from 0 to 300ish?

Thank you again for your time, and posting the correct info here for myself and anyone else going forward.

[TehLlama]

For starters, the 36/300 yards zero only applies to M855 being fired from a 20" NATO chambered barrel (or a 20" barrel with ammunition that has an identical BC and MV). Secondly, do you know what the most commonly missed targets are on the US Army 300 meter pop-up target qualification?
.....

I missed these posts.

I prefer a 200yd zero, a 50yd is a good facsimile for shorter range stuff for any application involving a red dot sight.
For a shorter than 14.5" setup where terminal effectiveness even with ideal loads (thinking 70grTTSX, 77grSMK, or similar) starts to diminish beyond 300m, then I'm certainly not going to try and maximize the POA/POI correlation at longer range when that weapon system shines in realistically closer ranges - again 200yd zero is usually the most attractive for me, as the first intersection is still close to 50yd, and anything within rock-throwing distance I'm never going to be hitting more than 2" below the center of the dot anyway.
Magnified optics with some form of BDC there's already an established procedure where a de facto 100yd zero works, so those are another case... there is a rare instance where zeroing an M16 (or other 20" barrel) with M855 at 36yd using the 300m top of the BDC on an ACOG works perfectly, but that's more of a special case than a really good general scheme of getting a useful BZO.

With a 4MOA dot, on a 16" carbine, with a 200m zero: using a startling variety of loads, the POI is going to be occluded by the red dot from 15-300 yards, which is awesome. As Molon illustrated, zeroing closer than 50yd tends to result in a significant hold-under from 80-160yd for a lot of combinations, and still not ton of useful POA=POI overlap beyond that.

[Molon]

Molon, this is what I am getting with the following Info:

Speer Gold Dot 24448 64gr out of 14.5 barrel:

Weight - 64 grains
B.C. - .267
Velocity - 2588


Zeroing Weather - 75 degrees F - 396ft above sea level - Pressure: 29.53 Hg

With that info, I get this:


Yards | Inches
5= 2.2
15= 1.4
25= .70
36= 0 - Zero
50= -.8 high
75= -2.0
100= -2.8
125= -3.2
150= -3.1
175= -2.6
200= -1.6
225= 0 - Crosses Zero
250= 2.1
275= 4.8
300= 8.1
325= 12.2

Does this look more accurate? Again, in my head, I basically just like that this zero gives me 3 inches high and low out to 260 yards. I misspoke earlier in my post, and even with this one, I am second guessing my work.

the whole point of my personal research was to have the "tightest" overall group (height-wise, up and down) from 0 yards to roughly 300+/-. Molon, with this combination of my setup, the 14.5 colt and the Speer 24448 rounds, is there, or do you recommend a better Zero to use that will yield a smaller overall spread from 0 to 300ish?

Thank you again for your time, and posting the correct info here for myself and anyone else going forward.

Based on your newly posted metrics . . .


https://app.box.com/shared/static/8l9kdur09pv9n3yeufcbpvs576a47f9i.jpg



....

[teksid]

I'm personally a fan of a 50m Zero on a RDS equipped Rifle/Carbine. Gets me to 200y with no holdover and hits 300y holding Top Edge of a 12" Plate, yet rises no more than 1.7" above Line of Sight... this is with M193/M855/Mk262

That what I do. I used to zero my rifles at 100yds until I realized how much easier the 50yd zero is to guess.
https://vimeo.com/132578570


Sent from my iPhone using Tapatalk

[HD1911]

and actually, for those interested, look at your Ballistics Calculator, and notice the differences (Trajectories) between the 50 YARD and 50 METER Zero... I personally use the 50 Meter Zero. They are obviously pretty similiar to each other... I just happen to like the 50m over the 50y due to a little less overall rise above LOS... just my preference.


50 Meter Zero:

http://i102.photobucket.com/albums/m119/HD1911/Mobile%20Uploads/DFBD26F9-EE55-444B-85F5-D2628C9FEF49_zpsb4k1jzzf.png





50 Yard Zero:

http://i102.photobucket.com/albums/m119/HD1911/Mobile%20Uploads/836515CF-ADDF-451A-A685-4E800BAF0ADC_zpso2obfocz.png

[tom12.7]

I remember a carbine class in the early 90's before the ban that left a lasting touch on me about zeroes. It was an advanced class that required going through prior classes, but it really wasn't a hardcore class. There was a prerequisite that all rifles had to be zeroed prior to attending the class. It started by everyone verifying their zeroes, with no direction or instruction at all. Then the instructor gave us all targets, we started at 1 yard, shot five rounds, swapped targets, went to 25 yards, and repeated every 25 yards out to the end of the 250 yard range. At the end of that, the instructor gave us a fresh target and a marker and had us mark all the hits on the target. Then he asked us if we were confident in our zero and why, many people seemed shocked from the results. We then adjusted our sights for our 1-250 yard type adjustment, repeated the process, and continued the class. That was done with iron's, but the basic concept is the same with a red dot. Define the reasonable distance that's intended with how much of a deviation from target center you can accept. The pattern is kind've elliptical, but if you can apply that concept in a way that suits the users needs, why not use it.

[TehLlama]

and actually, for those interested, look at your Ballistics Calculator, and notice the differences (Trajectories) between the 50 YARD and 50 METER Zero... I personally use the 50 Meter Zero. They are obviously pretty similiar to each other... I just happen to like the 50m over the 50y due to a little less overall rise above LOS... just my preference.

If I can validate a zero at 200m, (or 200yd) I won't hesitate to, but for the kind of precision I'm capable of with a red dot they're pretty interchangeable.

Still, that's a good illustration of how different they could be at 300-400.

[FromMyColdDeadHand]

If I can validate a zero at 200m, (or 200yd) I won't hesitate to, but for the kind of precision I'm capable of with a red dot they're pretty interchangeable.

Still, that's a good illustration of how different they could be at 300-400.

I have my rifles at 50y, but years ago I looked at tables and it seems like a 33y (maybe for 193 or 262 out of a 16inch?) would keep a round in the T1 dot from like 25 to 300 or so yards. You're shooting into a red hole- or red halo with my astigmatism.

[TehLlama]

I have my rifles at 50y, but years ago I looked at tables and it seems like a 33y (maybe for 193 or 262 out of a 16inch?) would keep a round in the T1 dot from like 25 to 300 or so yards. You're shooting into a red hole- or red halo with my astigmatism.

On a precise rifle, sure - considering that my cone of accuracy on rifles that wear micro aimpoints is a lot closer to 2MOA with defensive ammunition (taking me out of the equation) that still leaves some off the high or low end, especially if I'm not doing my part well - since I don't do speed without a tradeoff in precision, I at least want to maximize the accuracy side - and past 250yd I'm fine with having to consider a holdover, since those are going to be comparatively deliberate shots anyway. The happy convenience for me is that the 100m POI is right at the top of the dot, so for those uppers (in my case Mk18 + can, Lightweight 14.7", Lightweight 14.5", Lightweight 16") I'm well within how much inaccuracy I'm introducing to the system all the way out to the really effective envelope of my best loads (Mk318, Mk262, 75gr TAP) from those barrels.

I'm on the opposite end of the vision spectrum - 20/8 or so, which lets me figure out some rather silly subtensions with the 4MOA dots.

[sevenhelmet]

I'm on the opposite end of the vision spectrum - 20/8 or so, which lets me figure out some rather silly subtensions with the 4MOA dots.

Wow, that makes me feel blind at 20/15.

As for the OP, a good question that, surprisingly, hasn't already been asked is "what do you want to do with your rifle?". I like to sight defensive/red dot type rifles in at 50m, and precision rigs at 200m for MIL indexed sights (or 50/200 yards for sights indexed in MOA). Since your rifle is a red dot, I would sight it in at 50. IMO, the OP's 36/300 yard zero is too "deep" a difference between near and far zero for solid hits at all the ranges in between. At 50/200, you have a much better chance of achieving the intended POI.

Plenty of technical data in this thread! This is why I like M4C over Brand-X.