Rifles

Different Zeros For Different Heros

Looks like I opened a can of worms with yesterday's post regarding the 50/200 yard zero. The amazing discussions that followed prompted me to look into and compare several zero distances including 25, 36, 50, 100, and 200 yard zeros.

I tried to get creative with the title of this post since I wanted to incorporate the word zero with the saying “different strokes for different folks” and make it rhyme. It kind of works. I think. But that’s not important. The point is the recent post with my analysis of the 200 yard zero generated a lot of discussion (mostly on Twitter) about its purpose, different zero distances and their purposes, and the pros and cons of the aforementioned zeros. It was a fun post to write and a magnificent discussion.

While I was under the impression the 50/200 yard zero came from hunters, there were several comments about folks being taught different zeros while undergoing military training. Some of the zero distances that came up included a 1″ low 25/100 yard zero, a 25/300 yard zero, and a 36 yard zero to name a few. Several used meters instead of yards. Quite a bit of discussion revolved around the 5.56 NATO cartridge as well. Another person pointed out that the 50/200 yard zero is based on the concept of maximum point blank range (MPBR). At any rate, I want to explore some of these a bit.

I’m going to take a minute first here to remind returning readers and inform new readers that I’m just a civilian with relatively limited hobbyist experience when it comes to rifle shooting. While I’ve received some training, it’s not extensive. As such, consider my commentary here to be novice observations with a dash of ballistic nerd opinion. There are plenty of authoritative sources on this subject. I’m not one of them. I will also ask all of you to correct me if I end up making incorrect statements or have used bad assumptions.

I’m going to start by explaining my understanding of MPBR because I think this concept plays a large part in deciding to apply some of these zero distances. I understand MPBR to mean the distances at which a target of a known size will be reliably hit without having to adjust the sighting system or apply a hold over. The implication here is that as long as a target is contained within that known range the shooter can confidently center the aiming system on the target and confidently count on a good hit assuming the shot fired was fundamentally sound. This can be extremely useful when needing to make a shot under pressure such as a defensive encounter or while hunting game animals while experiencing the increased heart and breathing rates (along with all of the other physiological changes) that occur under stress. A fundamentally sound shot is still required, but there is no additional critical thinking required to calculate and apply adjustments before taking the shot.

Okay, let’s look at them zeros! I’m going to start by looking at zeros using the ballistic data from a standard 55 grain FMJ 5.56 NATO (M193) round. Why? Because, as previously mentioned, most of the discussion around these zeros seems to circle around the 5.56 NATO cartridge and the 55 grain FMJ variant is what I most commonly see available in my neck of the woods. Don’t worry, I’ll explore others.

25 Yards36 Yards50 Yards100 Yards200 Yards300 Yards
0″1.04″2.33″6.29″10.81″9.57″
-0.75″0″0.87″3.37″4.98″0.83″
-1.19″-0.64″0″1.63″1.49″-4.41″
-1.60″-1.23″-0.82″0″-1.76″-9.28″
-1.37″-0.91″-0.38″0.89″0″-6.62″
55gr FMJ 5.56 NATO – 3240 fps – .243 G1 BC – 2.6″ sight height

First off, the velocity I used is an advertised velocity that was acquired using a 20″ test barrel. As far as I know not many folks are running AR-15 chambered for 5.56 NATO with 20″ barrels. So keep that in mind.

As I started looking at the trajectory data, the first thing I started wondering was what applications would I use an AR-15 in this chambering for. Personally, it would either be for defensive situations, varmint/predator hunting, or competitive shooting. Generally speaking, that means the targets I would be dealing with would vary from as small as 4″ up to as large as 8″ in diameter. Given those known target sizes, I’m going to look for the zero that provides the best (widest) MPBR. So what I’m looking for is a zero distance for which the path of trajectory doesn’t deviate more than 2″ high or 2″ low (for a total spread of 4″ corresponding to the size of the smallest applicable target) from the point of aim for the longest possible distance. The idea is that a shot fired while aiming at the center of the target will impact the target area because the trajectory of the projectile will stay between the top and bottom edges of the target. This allows us to focus on the target without having to worry about a hold over or holding the edge of the target as long as the target is within the MBPR range.

Based on this data, I’m going to go ahead and toss out the 25 yard zero idea for this cartridge since it begins to exceed that upper 2″ limit at 50 yards. The 36 yard zero is the next worst offender as it first exceeds that limit at somewhere before 100 yards. Out of the remaining zeros which are good beyond 200 yards, the 50 yard zero has the least deviation at 300 yards. This suggests a 50 yards zero provides the best MPRB for this cartridge and rifle combination. This also contradicts my suggestion in the last post to always zero in at 200 yards instead of 50 yards. What can I say, I’m not perfect and I’m still learning.

Turns out there is a shooting calculator to help determine the maximum point blank range for a given cartridge using the projectiles ballistic coefficient, initial muzzle velocity, sight height, and target size as inputs. The calculator also provides a “sight-in at 100 yards” value which can be used to sight in the rifle at your 100 yard range and “zero” it high or low to the point of aim to get the best MPBR. The calculator also provides the distance of the near zero, the far zero, and the minimum and maximum point blank range. For this cartridge the calculator provides an optimized point blank range for a 4″ target with near zero of 51 yards yields a far zero at 232 yards and a point blank range from 10 to 266 yards. That’s pretty close to the 50 yard zero we eyeballed with the trajectory data in the table.

M193 trajectory with 51 yard near zero and 232 yard far zero

Okay, let’s do this again with the 62 grain M855 cartridge instead and see what we get.

25 Yards36 Yards50 Yards100 Yards200 Yards300 Yards
0″1.04″2.30″6.14″10.24″8.73″
-0.74″0″0.85″3.23″4.44″0.03″
-1.17″-0.63″0″1.53″1.03″-5.09″
-1.56″-1.18″-0.78″0″-2.04″-9.68″
-1.30″-0.81″-0.26″1.02″0″-6.62″
62gr XM855 5.56 NATO – 3020 fps – .349 G1 BC – 2.6″ sight height

This data is pretty similar to the M193 data we’ve already looked at. In my opinion, I would use the M855 cartridge for the same applications as M193 and will therefore apply the same criteria to end up selecting the 50 yard zero to optimize the point blank range of the cartridge.

The point blank range calculator provides very similar results as well suggesting a near zero of 49 yards with a far zero of 228 yards and a point blank range from 9 to 263 yards.

What about those 77 grain Mk 262 heavy boys? I’m going to short circuit the table generation and plug in a 0.372 G1 BC, a 2720 fps initial muzzle velocity, 2.6″ sight height, and 4″ target directly into the calculator instead. The results are still closer to the 50 yard zero than any of the other zeros with a 45 yard near zero, a 208 yard far zero, and a point blank range from 9 yards to 240 yards.

Let’s change things up and look at the other NATO cartridge common in the United States, the 7.62x51mm or the M80

25 Yards36 Yards50 Yards100 Yards200 Yards300 Yards
0″1.02″2.26″5.90″9.20″6.45″
-0.74″0″0.83″3.04″3.47″-2.13″
-1.15″-0.61″0″1.37″0.14″-7.13″
-1.50″-1.11″-0.69″0″-2.60″-11.24″
-1.17″-0.64″-0.04″1.30″0″-7.33″
149gr FMJ 7.62 NATO – 2790 fps – .456 G1 BC – 2.6″ sight height

As a hobbyist looking at this data, I don’t see a significant difference between the data in the 7.62 table and the 5.56 tables. The applications remained constant and I was picking a zero to optimize the MPBR for 4″ targets. I’d still opt for the 50 yard zero. Although the difference between the 50 and 200 yards zero is pretty close to negligible.

Putting this data into the MPBR calculator for 4″ target applications I get a 46 yard near zero with a 217 yard far zero and a point blank range from 9 yards to 251 yards.

Let’s say I wanted to optimize the MPBR for hunting medium sized game animals and didn’t worry about smaller target applications. For this application, the trajectory path deviation widens from 2″ to 4″ (for a total deviation spread of 8″). This change makes the ideal zero a 36 yard zero which provides an exact 36 yard near zero, a 273 yard far zero and a point blank range from 0 to 319 yards. I purposely ignored this application when looking at the 5.56 cartridges simply because it’s not an application I would use those cartridges for.

7.62 trajectory with 36 yard near zero and 273 yard far zero

Looking at the possible deer hunting application of the MPBR concept has me wondering what things could look like for the current 6.5mm Creedmoor cartridge I use to go deer hunting with. Let’s have a look.

25 Yards36 Yards50 Yards100 Yards200 Yards300 Yards
0″0.55″1.16″2.56″1.28″-5.94″
-0.39″0″0.40″1.04″-1.75″-10.49″
-0.59″-0.29″0″0.23″-3.36″-12.91″
-0.65″-0.38″-0.11″0″-3.82″-13.59″
-0.17″0.31″0.84″1.91″0″-7.87″
143gr ELD-X 6.5mm Creedmoor – 2700 fps – ..625 G1 BC – 1.5″ sight height

Things get really interesting here when I consider these zeros to optimize the MPBR of the hunting rifle (note the lower 1.5″ sight height) using the specific Hornady 6.5mm Creedmoor hunting load I’m currently using specifically for 8″ targets. The first thing to note is that all of the zeros are suitable out to 200 yards and all exceed the 4″ trajectory deviation before the 300 yard mark. The one with the least deviation is the 25 yard zero which suggests this zero would be optimal to maximize the MPBR for 8″ targets. Frankly, without using the calculator that’s what I would use.

6.5CM trajectory with 21 yard near zero and 260 yard far zero

Using the calculator I get an optimized MPBR with a 21 yard near zero, a 260 yard far zero, and a point blank range of 0 to 307 yards. I’m honestly extremely tempted to sight in my rifle with this 21 yard zero and give it a go this hunting season. Especially since I really can’t do too much precision work with the reticle in the scope I have mounted on the rifle and the lack of external turrets.

So what’s the take away from all of this?

First and foremost, it seems that my suggestion to always sight a rifle in a 200 yards when looking for a 50/200 yard zeros isn’t necessarily good advice (like the blanket advice that is sometimes too common in the gun community regardless of how well intentioned it is). Especially, if one is looking to optimize the MPBR for their rifle and ammunition combination.

I think this concept of MPRB has some very promising implications for a lot of applications especially those with less complex sighting systems such as traditional iron sights, red dot sights, or scopes with simple reticles and capped turrets. Definitely something I want to play around with and put to the test at the range. I haven’t considered the implications of using anything other than a 100 yard zero with an exposed turret scope that includes a Christmas tree reticle or anything other than a 200 yard zero with scope that includes a BDC reticle.

Last but not least, it’s important to think critically because there is always more than one way to skin a cat. Be wary of commonly parroted advice, especially if it’s presented as a silver bullet without qualifiers.

As always, your mileage may vary.

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