The 2 Common 5.56mm Zero Schemes

Praxis made a useful comment on my 5.56 holdover infographic:

Recognize that the point of impact for all of these aim points is the 300 dot high center chest. So with a 25/300 zero if you take an aimed head shot at 100-200 you will miss high. The 25/300 zero is an infantry zero that trades an area hit probability gain and gives up near range precision. You can run trajectories through JBM ballistics online. MV, sight height, and BC are the most relevant inputs. For most realistic and effective engagement ranges for civies and police an approximate 50/200 zero is more practical.

It’s a good point, and it stands. The long and short of it is that soldiers with battle rifles should use the 25/300 zero, while CQM carbine shooters should use the 50/200 zero.

The 50/200 is flatter shooting. The 25/300 zero has a max ordinate (the highest point in the trajectory) of 6.69″ at 175m, with the M855 round. The 50/200 has a max ordinate of 1.99″ at 123m. Essentially, the 50/200 zero is point of aim, point of impact from 0-230m. Your drop is 5 feet at 500 meters, so this zero is very unsuitable for medium range targets.

A Battle Sight Zero for the 30-30 WIN

Several WRSA posters asked for a BZO graphic for the 30-30. Here it goes. I chose a 200 meter zero because this is a medium game round, and this zero is point of aim point of impact within 4″ between 0-230m.

A Battle Sight Zero for the M-4

There is an old school graphic for the M-14 (7.62 NATO) which has been floating around for awhile now (hat tip WRSA). The point of the article and graphic is for a shooter to have a single zero, and to memorize holds.

This is a great concept for carbine shooters as well as battle rifle shooters. I have made an updated graphic for a new generation of gun owners. This is for the M-4 series of weapon, firing the M855 or M193, with the standard Army 300 meter zero. At this zero and these rounds, the holdovers are correct due to the higher MV of the M193 balancing against the higher BC of the M855. Use the comment section to tell me what other graphics to make. Without further ado…

 

If you like the infographic, you’ll love Sendit Ballistics for iOS.

Deer Behavioral Patterns

Timely article from WeaponsBlog on deer behavioral patterns. Of course, I already got my doe for the year…

As the rut progresses, vegetation begins to die off resulting in depletion of food sources in wooded areas, and the trees start shedding leaves. This is the time when the deer move into open areas in search of food but feeling insecure in such places they prefer to move around at night. During fall, deer movement is at its peak between 4 am to 8 am and 4 pm to 10 pm. The very little movement takes place between 8 am, and 10 am. Studies carried out to assist hunters in gauging deer movement have revealed the data. The deer travel the farthest distance during the morning hours perhaps because it has an urge to return to safe shelter before darkness sets in.

GIGO: Why Your Ballistic Calculator is Inaccurate

Sendit Ballistics, my own calculator, has a great reputation for accuracy. My algorithm takes a lot into consideration, and this results in excellent performance for medium to long range shots. However, the truth is that most all ballistic calculators will give reasonably good data.

While calculating trajectories in compressible flow (bullets flying quickly through air) requires advanced mathematics, it’s a fairly mature field. The reason your calculator gives you bad data probably has nothing to do with the calculator’s algorithm. Rather, it is a phenomenon known as GIGO: Garbage In, Garbage Out.

Your ballistic calculator relies on the following data, in order from the most important to least important:

  1. Ballistic Coefficient – This is generally a “G1” or “G7” class coefficient. All it means is that the bullet is benchmarked against a standard shaped object, and its performance is measured relative to that well known drag profile. You can get real nonsense if you input a G1 BC in place of a  G7 BC.
  2. Muzzle Velocity – Get this too wrong, and your range card will be useless past 500 meters.
  3. Weight – Inputing the wrong weight will make your bullet seem to perform better if it is too heavy, or worse if it is too light.
  4. Zero range – If you input the wrong zero range, by a large margin, you can easily get unhelpful corrections.

Less important: scope height, weather, twist rate, Coriolis effect.

Happy hunting.

Using Ballistic Calculators in the Field

Electronics versus DOPE Books

Handheld ballistic calculators are amazing gadgets that we couldn’t have envisioned at the start of this century. The ability to carry an Android, iPhone, or Kestrel device and have it provide accurate ballistic solutions is a serious advantage for a precision shooter in the field. In this article I provide shooters a simple procedure for making the most of electronic calculators in the field.

Ballistic calculators have generally supplanted DOPE books as the primary source of information for shooters compensating for bullet drop. I would urge serious precision rifle shooters to continue to collect DOPE (Data On Previous Engagements) during select shooting exercises, such as when the shooter knows atmospherics and range, and the target is small. In this way, the shooter can verify how accurate his chosen ballistic calculator is, as well as the data he has entered into it.

One way to use the ballistics calculator is to simply jam in your information, and take the shot. Of course, this approach introduces more problems: reliance on electronics, very slow correction time, and light in your face to name a few. At a minimum, you must have your rifle and load combinations pre-programmed.

An alternative way to use ballistics calculators is to use them the same way we formerly used our exhaustive collection of DOPE — to make a range card. Most shooters who are using military-style rifle setups will want to use 100 meter increments, and have their range card go out to 1000 meters or so. Notable exceptions would be police or small caliber shooters, who might want 50 or 25 meter increments, with a shorter max range.

For wind, I use a full value wind at 10mph. From this single point, it’s pretty easy to scale as needed for my 70% and 50% value winds, as well as differing wind speeds. As for elevation corrections that are in between range card ranges, just interpolate. While we know that trajectories do not change linearly, you can interpolate between the ranges as necessary and get close enough for government work.

Constructing the Card

Don’t use pen on white paper. It will become a sweaty mess, like when your mom washed your school clothes with a piece of homework in them. Rite-In-The-Rain is serviceable in a pinch. A laminated piece of paper should be the minimum acceptable range card. I wouldn’t even use that. It makes a target indicator, and isn’t as useful at night. A piece of cardboard, laminated, with luminescent tape is really cooking with oil.

Lum-tape allows the rifleman to see corrections at night.

My preferred range card is luminescent tape with a sliding window. I hide the majority of it, so that the shooter only sees two corrections through the window. This means it’s not such a huge honking light at night, and there is less of a chance of the shooter reading the wrong data entry. The rifleman can always remove the shielding for day use. The “window” is just a small cutout on one of the pieces of paper which can move up and down. See the procedure below:

Materials
  1. Brown construction paper (or spray-painted index cards), 3″ x 5″, 2X
  2. Stick-on laminate
  3. Luminescent tape, 2″ x 2.5″
Assembly
  1. Construct the shielding with a pieces of laminated brown construction paper. Cut out a window in the center of the paper, about 1.5″ by 2.5″. Cut out a tab at the top (and bottom if you wish), roughly 1″ by 2″. See below:
    shield
  2. Put the lum-tape rectangle on the bottom portion of your other piece of brown paper. You can make a full-size piece, but you’ll have to cover one of the halves for the window to work right. I do this, and just cover the top half with 100mph tape. Then, I have that extra space if I need it. Don’t write your corrections just yet, wait until the end. See below:
    card
  3. Laminate each piece of paper.
  4. Now you can write your corrections on the luminous portion with a map marker.
  5. Put the shield piece atop the range card, and move the range card up and down to put your desired corrections in the window.
  6. They aren’t connected in any way, so the shield can easily just fall off. Use the tape-on laminate to make two or three straps around the back of the shield. You’ll have to cover the sticky side on the back. Now you can simply slide the card up and down, and the two cards will stay together.
  7. See the finished product below:

There are numerous other techniques for keeping your hold-offs handy. My method is just one of them. In fact, I bet somebody in the comment section will have an idea which is simpler and better than mine. Good on them. Another good technique I know of is the tiny range card in the scope cap. Some optics manufacturers, such as Vortex, make these. You send them your DOPE, cap size, and money, and they send you a little insert.

Which Ballistics Calculator?

The science behind symmetrical projectile flight is fairly well-known by now, largely thanks to the work of the Aberdeen Proving Grounds. Those who are comfortable with calculus and compressible fluid flow should check out Robert McCoy’s seminal work on the topic Modern Exterior Ballistics.

That said, all of the calculators have slightly different trajectories. I have yet to come across a ballistics calculator that is truly terrible. Here are a few to get you started:

  1. Sendit Ballistics  – I programmed this app for iOS (Android coming soon), and I recommend it whole-heartedly. I have specifically designed this App to be “field-worthy,” featuring night vision mode, fast corrections, rapid switching between guns, and a range slider for changing targets. See the product page for more info, or download now. It’s free to 250m, and $4.99 to infinity.
  2. Hornady, Strelok, Ballistics AE – These are industry leaders, and work quite well. I believe that these Apps are wonderful calculators, but frankly over-designed for tactical shooters, and quite costly for hobbyists.
  3. Hornady online ballistics calculator – If you just want corrections to make a range card, use this. It’s free, and requires no iDevice.

Happy hunting.

Spray-Painting Things

This article is part of a series on the practical aspects of stealth. To see links to all of the articles on this topic, see the main page for The Stealth Fighter.

This article is on a simple, formulaic way to spray-paint gear in order to reduce target indicators.

By now, you should be picking up on a theme: Target Indicators. Eliminating target indicators is the key to staying hidden. When a trained observer spots you, he will not see a man hiding… he will see a perfectly straight, 4 inch line. Then, he and his friends will scour that area (possibly from 1000m away through a scope) in progressively larger circles until they find more target indicators. Consider the following story:

The scouting party stopped on the ridge just across the waddi, about 350 meters into the mid-morning sun. Most of the men drank water and stared at the ground. The trail man scanned your ridge with a pair of cheap binoculars. You sighed slightly as he scanned right over you, down to the bottom of the spur, upon the side of which you had been digging your team’s subsurface hide site about 60 seconds ago. You could hear every thump of your heart, firstly from the hard task of digging in the arid dirt, and secondly from the raw fear of your ghillie suit being critiqued by armed searchers as you lay helplessly exposed on a small hillside. Your ghillie was perfect. You’d spent hours perfecting it in the rear. But in your haste to flatten out, your black E-type shovel lay exposed only a foot to your right side. Did you dare reach out and pull it under your veil?

The trail man snapped his bino’s back toward you. Now the lazier soldiers had stopped murmuring to each other and were staring at your spur. Their movements took on urgency as they fanned out into a line. The man with the binoculars tossed them aside, and his boss was now yelling and pointing. Your chest tightened and you gasped for breath from the adrenaline surge. Should you call out to your two partners and start an immediate action drill? Is it possible the search party still didn’t see you? You felt the sand kicked into your face, and heard the thumping of machine gun rounds on meat before you ever heard the gunner let off his first string. The screaming and firing continued as your bright mid-morning faded to night…

This disaster could have been averted by not only camouflaging yourself, but also your gear. In this case, the searcher never saw you, the sniper, but he did spot a large target indicator in the form of a black, 30″ shovel. Let’s dive right into the solution:

The materials you need are as follows:

  • 2-4 flat camouflage spray paint cans. Olive green, tan, brown, and light green are good choices. I typically only use the first three.
  • A piece of netting for use in texturing. 1/4″ to 1″ squares is a good density. Don’t use fine mesh.
  • Masking tape for preparation.
  • Latex gloves, unless you don’t mind getting your hands camouflaged as well.
  • Somewhere to hang the item so you can walk around it, and not have to flip it on multiple sides.
  • A couple of pieces of vegetation common to the area.

The paint colors are designated as Base, Primary, and Accent. Primary is the general color you want the item to be. In the case of a shovel in an arid, rocky environment with space vegetation, I want it to be tan. Base color is the least important color. It fades into the background, and is really just for diversity. I’ll use green for this arid desert. Accent is what you use to add details to the item. Brown will work in this case

For a mountain situation, I would use green for Base, brown for Primary, and tan for Accent. In the woodlands, I would use tan for Base, green for Primary, and Brown for accent. In the desert, I would use green for Base, tan for Primary, and brown for Accent. For the example outlined below, we’ll assume a desert environment.

And now, the procedure:

  1. Before painting, you should prepare the piece of kit. In the case of firearms, tape up the sights and stuff an earplug down the barrel. Close dust covers, and consider taping off rubber-like pieces. Some petroleum-based materials aren’t harmed by paint, and some are. Tools should be sharpened. Items that collapse should be extended. In the case of the shovel you neglected to properly camouflage, I sharpened it with a file and extended it out.
  2. Next, hang the item up, and paint it with your base coat. Don’t be alarmed that this coat doesn’t look much like the intended environment. It will be mostly obscured. I have noticed that a surprising percentage of people cannot properly spray-paint. The correct technique is to make steady passes from about 12 inches away. It’s okay, and even preferred to “dust” the object multiple times in route to achieving the desired coating. If your paint is running down the object, you are wrong. If the item looks wet, you are laying it on too heavy. Back off, and speed up your passes. See my olive green shovel below.
  3. Now, we will add texture. Hold your piece of netting up to the object as flat as you can get it. Dust it with your Primary color. Be a bit more aggressive. Dust from 8″. You want to get start contrast between the netting and the item. Keep the netting flat, or the paint will go around it and just coat the whole item, without leaving the snakeskin pattern behind. You will have to do this piecemeal. See my mostly tan shovel below:
  4. Now, it’s time for accents. Grab some vegetation (at least two samples) that is representative of the area you will be going, and at the vertical level you and your equipment will be operating. What that means is that you should not use a grassy pattern for a piece of equipment that will be emplaced in a tree. Likewise, don’t use big tree leaves for something that will be on the ground. Use the Accent color, and spray over the leaves and grass.  If vegetation isn’t appropriate, use the Accent color to make a few broad tiger stripes across the item. Those broad stripes will cut it into smaller pieces, making the big target indicator into smaller ones. In this case, I’ll use leaves and grass. Take a look at these brown accents:
  5. Now, the shovel is just a touch too brown and dark. The final step is to rotate back to your primary color, and finish the piece of kit with a good dusting. Be careful not to simply paint the whole thing. In the case of this shovel, the idea is just to lighten the whole thing slightly. My background is fairly dark, and I don’t want it to be pure tan. This dusting is one last chance to smooth over lines and fix mistakes. See the final result below, after a slight tan dusting:

I cannot recommend enough that you spray paint your kit. It doesn’t hurt anything. It’s cheap, and easy to change. If you mar the finish, it’s easy to fix it. In the case of cloth items, you can use light, broad strokes to help break them up without saturating them with paint. Also, paint protects metal. And, as we saw from the introductory story, sometimes small remaining target indicators can cause major headaches.

7 Do’s and Dont’s of Follow-Through

“Follow-through” is what happens after the round fires. It can make or break your shot. When I was learning serious rifle shooting, I always found the instruction on follow-through to be a bit vague. I knew that it was bad to flinch, and that holding the rifle in a weak manner led to inconsistent shooting. I think that a thorough explanation of follow-through is helpful for shooters who may be having problems with it.

 

Slinging Bullets

Your bullet remains in the barrel for a while after you pull the trigger. For one, it takes time for the hammer to hit the firing pin. It takes time for the primer to ignite the main charge. It takes time for the main charge to burn enough to create enough gas pressure to force the the bullet to move. Then, the bullet still has to gain speed, and ultimately travel roughly 24 inches to leave your barrel.

How long is your bullet in the barrel? 0.0015 seconds, roughly. Here’s a proof. Skip it if you don’t care.

Let's work backward from the muzzle velocity and final position. Assume 2600fps, 24 inch barrel, constant bullet acceleration. These aren't perfect assumptions, but they'll get us in the ballpark. 

x = The position of the bullet. The position we care about is 24 inches, or 2 feet.

v = Final velocity. 2600fps.

a = Constant acceleration. We'll have to solve for this.

t = Time, the number we are after.
x = (1/2) * a * t^2   and   v = a*t, thus a = v/t
so, x = (1/2) * v * t
thus, t = 2*x/v
t = 2*2/2600 = 0.0015 seconds

That’s not a huge number, but it’s not nothing either. And, it doesn’t account for the stuff that happens before the bullet starts accelerating. If your barrel is moving between firing and the bullet’s exit, you are literally “slinging” that bullet.

It’s not enough to keep the rifle still up to the point of firing. You must also keep the rifle still until the bullet leaves. The key is a stable position.

Bottom Line

Do:

  • Use natural point of aim (NPOA). NPOA means that your body is relaxed before firing. To find it, close your eyes, get into a comfortable prone position, then open them. Ideally, your reticle will be on target. The more you have to bend your body to the target, the more “spring” you are introducing to the system. Much of that spring will release during firing, leading to poor follow-through. Close your eyes, reposition, and open them until you are very close.
  • Grip the rifle like a firm handshake. Don’t squeeze like a weirdo, don’t limp-wrist.
  • Eliminate flinch. Do ball-and-dummy drills with a friend, whereby the friend loads the gun, hands it to you, and you fire. He loads it with either a live round, or a snap-cap. It’s so embarrassing to flinch on the snap-cap that you will quickly stop doing it.
  • Pay attention to where your reticle resettles after firing. If it’s not back on the target, you moved a little bit.

Don’t:

  • Don’t get ahead of yourself. Be solid until well after the round leaves. AR shooters can hold that trigger, then slowly release to hear the sear reset. This is a great mechanism to enforce slowing down.
  • Don’t use a springy support like a weak tree, elbow-on-knee, or some other support that is likely to shift when a bit of force is applied to it. Shifting support = movement. Not good, given the fact that you need to keep that gun still for nearly 2 milliseconds prior to the bullet exiting.
  • Don’t try to constrain your barrel’s movement by resting it on something. This will bend the barrel, and will throw the round off. If you don’t believe me, go to the range and try it! It’s more than you’d think.

Happy hunting.


 

If you want to shift your rifle shooting into overdrive, check out Sendit Ballistics, in the Apple Store. Sendit Ballistics is simple yet powerful, and features night vision mode, range card, and immediate corrections. Input as little or as much detail as you like.

Non-Visual Target Indicators

This article is part of a series on the practical aspects of stealth. To see links to all of the articles on this topic, see the main page for The Stealth Fighter.

A target indicator is anything that makes your presence known to an enemy; it indicates a target (you, in this case). If you master this section, you can write the book on stealth. The purpose of camouflage is to reduce target indicators. The importance of the term “target indicator” is impossible to overstate. If you get just that from this article, it was worth your time to read it.

People spend an enormous amount of time on reducing visual target indicators. This article is on reducing your signature as a target in the domains of sound and smell. A misplaced radio crackle, or a whiff of cigarette smoke can burn you just as well as an errant movement. Let’s dive in.

Smell

In any field environment, perfumes stand out. The detergent you wash your clothes with is almost certainly scented, as is your shampoo. The simple solution is to keep your clothes for the civilized world and your field-wear separate. Wash your field wear in warm water with no detergent. It wont become rancid with stench, and yet it will not give you away. Similarly, avoid soaps, deodorants, colognes, and other such frills for a minimum of 24 hours prior to entering a field environment.

Another obvious olfactory target indicator is cigarette or campfire smoke. Don’t do it near the enemy. An unfortunate wind will leave no doubt as to your presence. Cooking food falls into the same category. You must eat, but use good judgement.

Perhaps one you didn’t consider is the food you eat seeping through your pores. This mainly pertains to situations where your potential observers are foreign. If you’d like to see this firsthand, get extremely drunk. The next morning, go for a jog. You’ll smell the booze seeping out. If you prefer not to abuse yourself that much, eat a healthy dose of curry and breathe in the same effect later.

Sound

Some sounds belong, and some don’t. The clanking of metal is sure to draw attention, as is the ringtone on your cell phone. Make sure that whatever sounds you make in a given area of operations belong, or don’t make them at all. Discipline is obviously a key factor.

The way you walk is also a target indicator. If you observe animals in the wild, you’ll note that they never just go tromping through the woods. They walk a bit, then stop, walk a bit, then stop. Crackling leaves and sticks on their own are not a definitive target indicator, but nonstop crackling indicates human movement.

Velcro, radio squelch, water sloshing, the thudding of feet on earth, coughing, and the rustling of paper and plastic are a few other sounds I can think of that cannot be easily explained away . During the Vietnam War, prior to hydration bladders, small recon teams would pass a canteen and empty it to avoid sloshing. I like to tape the metal tabs on zippered pouches, or replace them altogether with gutted 550 cord.

Weather plays a significant factor.  On cold days, sound seems to travel further. This isn’t an illusion. Sound refracts downward from warmer air toward the cold ground, which results in more sound making it further downrange prior to the sonic energy dissipating. The animals are a good bit quieter. The dried leaves and sticks crackle much more loudly than in summer. A cold, calm day is a terrible time to attempt stealthy movement.

During wet weather, leaves and sticks are muffled and make very little noise. While it may be miserable to be out in the field, you can be sure that your enemy is equally miserable, and the reduction in audible target indicators is welcome for the weary stalker.

In summary, don’t focus on purely visual target indicators. Sounds and smells can provide a searching enemy with a wealth of knowledge about your element. Don’t wash your field clothes with perfumes. Do use tape and 550 cord to silence metal and zipper elements on your kit. In the sounds and smells you make… be an animal.

6.5 Creedmore vs 5.56. One Datapoint

I am a proponent of the 5.56 for accurized rifles, but it has some limitations. Here’s a single datapoint to consider: A friend and I were shooting steel at 800 meters in a stiff wind. My friend was shooting 6.5, I 5.56. The Creedmore shooter had to hold off 3 feet to account for wind. I had to hold off 10 feet with my 5.56.

Food for thought when considering the merits and limitations of 5.56 precision shooting.