Archive | August 2014

Getting Your Inputs Squared Away Part: 5

Let’s start now by determining what we need to about the weapon system.

Rifling Twist: If you don’t know already this will have to be identified or measured. Identification is pretty easy nowadays. Most people are shooting off-the-shelf rifles by major manufacturers who advertise their twist rates. AR shooters will very often find the twist rate marked on the barrel somewhere. If neither of these are there for you then take a cleaning rod and set up a patch jag with enough patch material that it fits really snugly in the bore. Mark the cleaning rod at the top with white out so you can tell when it has turned completely 1 time. Get the patch started and push it all the way in. Now slowly pull it out allowing the rod to rotate. When the mark makes one complete revolution mark the rod again. Remove the cleaning rod and measure the distance in inches between the two marks. That number is your twist rate. If you have 8:1 then add “8” in the box. If you have 12:1 then add “12” to the box.

Scope Height: Getting this right is important for a number of reasons. It’s best to use micrometer or some similar instrument that will give you accurate readings down to .01 inches. Measure from the centerline of your scope to the centerline of your bore. You could do the centerline of your scope to the centerline of your bolt as well. How ever you do this step you want center to center vertical distance. My scope centerlines tend to sit 2 inches or less above my muzzle. On AR-10/15 platform rifles with carry handles or PEPR type mounts that number can get up near 3 inches. Keep your scope low if you can.

Rifle Weight: This isn’t as critical but if you want something approaching a useful measure of recoil energy then get it as close to perfect as you can. My rifles vary in weight from 6lbs to 18+lbs.

Reticle: Do you have a ranging reticle? It’s a good idea to use a ranging reticle because it gives you the ability to hold-off minor adjustments that you don’t have time to dial in. All reticles have something in them that will obscure (subtend) some portion of the target behind it. You can measure it or you can check with your scope manufacturer for details. You can even ask me and I’ll help if I can. If you have an MRAD subtended reticle (Mil-Dot, Mil-Quad, G2DMR, etc…) then add a “Y” to the box. If you have a ranging reticle that is set up to subtend minutes of angle then leave the box blank.

Turrets: If your scope turret adjustments are in MOA leave the box blank. If you click off MRAD’s then add a “Y” to the box. This is critical. If you don’t know, ask the scope manufacturer or even me. I’ll help if I can.

Boat Tail Bullet: This dramatically affects the velocity decay rate and actually dopes the ballistic coefficient. If you’re using a flat base bullet or hollow base bullet then leave this blank. If you’re using a proper boat tail bullet then add a “Y” to the box.

Now you’re almost there. The only things left to deal with are the real core ballistics elements. In order to get Part 6 done you’ll need to be ready to get out to the range for chronograph work before you can attempt the next part so grab up 50-100 rounds of your favorite long range ammo, get yourself a small cooler and get a nice full box of cheap-ish blasting ammo. Take that blasting ammo to the range and get your rifle zero’d at 100 yards (that’s my recommendation, see below for more on that). If anything isn’t right, you need new rings or whatever, get that done. Your weapon system has to be field ready before we move on. Once we finish the next bit and some range work you’ll be ready to get out and start making hits at long range. You’re going to need a chronograph for Part 6. They’re not that expensive. 80 bucks at Midwayusa.com for a Chrony. You’ll also probably need a tripod that you can mount your chronograph on. A decent tripod is 20 bucks. A great one is infinity dollars. Pick one that you like.

A note on Zero Range: 100 yards is fine for most people. I shoot out to a mile with a zero range at 100 yards. Military combat snipers may find it more useful to zero a 7.62x51mm NATO rifle at 400 or 600 yards but that is not due to any desire for precision. Combat means fast fast fast and the targets shoot back. For civilian shooters we’re going to dial a solution more in the way an assassin might operate. We’re not in a rush for the most part. Setting up for 100yrds will let you zero at a range you can walk to quickly and that you can see well from the bench through the scope. There are other benefits. Suffice it to say, my recommendation for civilians is 100yrd zero.

Stay tuned for Part 6.

Getting Your Inputs Squared Away Part: 4

Ok, you’ve got your text fields done and your barometric pressure measurement done. Now we need to do some of the inputs that have math done against them. These will affect your solutions so it’s important to be as precise and decisive as possible.

Let’s start with the yellow boxes: Metric Distances, Heading, Transonic Velocity, MOA:MRAD:Inch, Hectopascals. These are yellow because it’s encouraged that you leave them alone unless you know that you need to change them. They’re set with values that will give the broadest utility for most shooters.

Metric Distances: This is just to set the system to use metric distances for range. If you’re a metric system user you should actually leave the box alone and let the “Full Metric” option select it for you. In fact, it’s meant to be properly set up without any user input for those that use SAE ranges and for those that use metric ranges. For those rare sets of Americans that use metric ranges instead of yards but use SAE measurements for everything else will be the ones that want to put a “m” in the box. Putting an “m” in the box (lower case) will force the system to use meters for distances both large and small which are measured in linear distance. Angular distances will not be affected.

Heading: Leave this alone. It’s critically important for Coriolis calculations and it’s set by default at 90 to give you a full value. Your actual heading during firing will change but you actually use the cosine of your angle away from north or south as a multiplier for shots not facing directly east or west. In any event, you should leave this box alone.

Transonic Velocity: This is basically the point at which Ballistic_XLR will stop calculating. The reason for this is that when bullets go transonic they’re typically going to become unstable or at least less stable and any numbers that Ballistic_XLR provides after that are going to be wrong. If you know that your bullet is acting stable further then you can lower the number to as low as 1050. Note that doing so is unsupported and whatever results you get from that are considered spurious. Basically, leave it alone.

MOA:MRAD Inch Equivalence: Angular units of measure get translated to linear measurements in one of two ways. Either the distance is tracked as denoting the arc between to angularly separated points or traversing a straight line that transects both points. The first method describes a curve, the second method a straight line. Since curves are longer there is an opportunity for engineers to not make life easy. Some scopes use 1.09″:MOA@100yrds as the standard. Most use 1.05″:MOA@100yrds. At least one model of scope I’ve encountered used 1.01″:MOA@100yrds. This leads to some scopes always dialing in 4% more or less dope than they need. If you’re always coming in 4% high or 4% short in your initial adjustments, try changing this value to 1.09 or 1.01. Many Nightforce, Leupold and Sightron scopes have shown this feature. It’s best to do a scope calibration test at the bench to verify your click value. I’d do it at 300 yards too. We’re talking about .04″@100yrds. That’s 1.2″ at 300yrds and thus it is substantially easier to discern the difference at longer ranges.

Hectopascals/Millibars: If you are using this then you’re almost certainly using full metric. If you’re not using the full metric option then just leave this blank. If you are using the full metric option then filling this box in with your current Hpa value and adding a “Y” to the box immediately above it will convert your pressure to inHG and add it to the Barometric Pressure box at A9. This is meant to save you the hassle of converting numbers and lets Ballistic_XLR provide data for metric system users and Imperial systems without making things too complicated.

Stay tuned for Part 5.

Getting Your Inputs Squared Away Part: 3

Text Fields. Text Fields. Text Fields.

All the stuff that’s greyed out in column B on Pocket PC inputs is greyed out to denote that the field to the left is meant for text. It’s meant to give you a way to help you discern one set of data from another. We’ll move from top to bottom.

Bullet ID: This is the name of the projectile you’re using coded for easy reading by you. I often use Hornady 154 grain SST 7mm projectiles in my 7mm Remington Magnum loads. It’s one of my favorite bullets. So I code it as H7SST154 and enter that in the box in column A. It’s nothing to do with the cartridge, just with the projectile. If you’re using retail ammunition then you’ll need to identify which bullet it’s using so that you can get the projectile specific ballistics data. It is critical that you select the correct bullet. Some makers make multiple projectiles with only subtle differences between them that dramatically affect the ballistic coefficient. Occasionally this requires a little research. If in doubt, call the ammunition manufacturer. If you ask for support the first thing I’m going to do is try and make sure you have the correct bullet data and it will help dramatically if you already have your projectile information correct. If you need help figuring it out, reach out to me and I’ll see what I can do.

Rifle Model: M70, M700, M10, M110, M70-5R, M91/30, etc… This is the model of rifle. If you’re like me you may have multiple rifles in the same chambering. Let me be clear here. YOU DO NOT USE THE SAME SET OF DATA FOR BOTH RIFLES. They each will have their own personality and they should have their own data. I have at least 3 7mm Remington Magnum rifles and none of them shoots the same as the others at extreme range so I treat them differently and develop data for each. I put M70 or M110 or whathaveyou in the Rifle Model box so when I pull out a set of data for a 7mag I’ll know I’m pulling the data for that rifle.

Barrel Length: This isn’t going to be super helpful to many folks. You might notice as you develop your data that long-ish barrels tend to pump velocities a little bit and shorter ones tend to pull it out. It’s here for you to use. I put the data in just because it’s there. I also have multiple firearms in the same calibre, sometimes in the same model rifle so anything I can use to distinguish between the two can be helpful.

Muzzle Device: Are you using a brake? 1-port, 2-port, etc…? Are you using a suppressor? Are you running a plain Jane muzzle? Is your crown special on this rifle? This is a way of identifying further the weapon system being used. It’s also a way of characterizing some performance aspects of the rifle. If you’re unfamiliar with muzzle brake pull-off you should check out TiborasaurusRex’s Sniper-101 Part 55 Muzzle Brake Pull-Off Effect video. If you have a brake or suppressor then you can also look differently at the data given by the recoil calculator depending on how effective your brake is.

Operator: Give yourself some credits. Do you have a nickname? This is where to put it. One of the few things we can do in long range shooting that involves a sense of humor is setting up our handle/nickname. You don’t always want to use your real name. Sometimes it’s about being in character but usually it’s to do with OpSec. I’m “MeccaStreisand” in most of my online activities but I have other nicknames that are relevant in other realms. My spotter is colloquially called “The Disco Tripper” and his sheets have TDT in the operator box. Mine usually have MS.

NOTE: The next several are meant for handloaders that may have multiple recipes in use. These fields are still totally optional.

Chambering: Well this part is kind of obvious. I shoot at least 4 chamberings at long range from .223 to 7mm RM. It’s interesting that they share similar trajectories up to a point but after that they diverge drastically from each other. This is also helpful if you shoot more than one rifle with the same projectile but in different chamberings. 7mm RM and 7mm-08 is a combination that springs unbidden to mind. Both could easily use the same bullet and they’re ballistically pretty far from each other so it’s a good idea to differentiate the data for one from the data for another. I would avoid long words like Remington being spelled out. For 7mm Remington Magnum I input “7RM”. For commercial spec .223 Remington I put “.223Rem” in the box. For military spec AR-15 .223 cal I put “5.56x45mm” which denotes it as being high-pressure military spec.

Gunpowder: To be clear, this is for handloaders only. You don’t need to pull apart retail FGMM ammo to try and identify the powder it’s got in it (it’s been done already anyway). This is just which powder you’re using. Not how much. When I use IMR 4350 I put in “IMR4350”. When I use Varget, I input “Varget”.

Gunpowder Charge: Your chosen ammo is a single spec which provides specific performance and accuracy and precision criteria. If you change your loads you need to re-characterize it and find out how it performs again. It’s like starting from scratch. Track your powder charge if you handload and make sure you stick to it. If I use 68.2 grains in the load then I input “68.2”. Notice there’s no letters in there. You can but the display fields are super narrow for this so keep it short.

Primer: I like CCI #41 and Federal 215 and Federal 210 primers which I code as “CCI41” or “F215” or “F210”. You want to keep this short. The text field isn’t big for this on the tabs.

Case: This is flexible. You can do this however you deal with it. If I’m using mixed brass then I’ll input “mixed” in there. If I’m using all carefully trimmed brass then I’ll put in the manufacturer head stamp and the length. So for my .45Cinderblock I put in “SL460R-888” which means: Starline, .460 Rowland, .888 TTL. You can code it how you like it but again, keep it short.

COAL: Cartridge Over-All Length. This is defining your seating depth and rifling engagement and is one of the most important bits to be consistent about. This should be a decimal value number. “1.720” or “2.755” or “3.850” or whatever. Don’t guess. Get a set of calipers and measure. You can use millimeters too. 44, 70, or 98 works just as well.

Now you’ve got all your text fields filled out and your printed data sheets will look pretty and complete.

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Getting Your Inputs Squared Away Part: 2

Ok you went out and bought yourself the Kestrel 3500 and you got it set up like we discussed in the previous article. Now, go outside and measure your barometric pressure. Now take a drive to where you shoot long range. Get a pressure reading there. Now you’ve got a single set of data points. You’ll want to do this a few times so you can get a running average and the daily standard deviation and extreme spread and coefficient of variation for the places you shoot. You can use the Shot Log & Statistics page of Ballistic_XLR to find the statistics for your BP measurements. Once you have your statistics you’ll be able to make an intelligent decision about what base BP setting to put in your charts.

I live about 80feet above sea level and right next to the coast so my BP is usually sitting pretty high. Day to day I see 29.5, 29.3, 29.8, etc… so it hovers around the middle of the 29InHg mark with a little bias toward the upper end of that. Living next to the coast though increases humidity which drops air density. So I set my tables up usually for 29.3InHg. That takes care of my average local humidity. When I go to the Mojave Desert I end up at 2800ft altitude which drops my BP to 27.7 or thereabouts and it crushes the humidity. Less humid air is more dense. So for that situation I’ll set up my tables for 27.8. What I’m doing there is doping the BP ever so slightly to accommodate large swings in humidity by adding or removing some air density which is exactly what humidity does to ballistic trajectories. A .1InHg increase or decrease in BP should be sufficient to take care of the full swing from 10% to 90%. I usually use a .1 change in BP for every 40% of humidity. So if I’m in the desert and it’s 20% humidity I’ll add .1 to BP. If I go out and find I’m shooting in 100% humidity then I’ll drop .1InHg from my BP.

So to sum up, set your BP to a solid representative BP for the area you shoot in. A decimal change in BP (using inHg) or a 5HPa change (in HectoPascals) is enough to throw off the shot at extreme range. At shorter ranges it’s the difference between hitting the bulls-eye and just being on-paper. Once you’ve got your BP nailed you’ve got your drop figured out.

Stay tuned for Part 3.

Getting Your Inputs Squared Away Part: 1

Why multiple parts? You’re going to have to buy some things in all likelihood and it’s best if I give you a week in between editions to make purchases and get them set up with the rest of your gear and learn how to use them and all that jazz.

First thing’s first: Garbage In, Garbage out. I’m not kidding. If you skimp on your data you’ll cut your maximum effective range in half or worse. Little things make a huge difference when the distances grow. You’re going to need to burn some ammo and you’re going to need to burn some more cash. You’re going to have to spend at least a pair of days at the 100yrd bench doing velocity logging. You’re going to have to spend a little time in the field testing your kit and making sure you’re able to make those shots.

To begin with you need a Kestrel weather meter. There might be other brands but quality matters and Kestrels are quality. You need temperature and barometric pressure and wind. There are Kestrel models that also provide ballistics data and humidity data, etc… Get the one that fits your budget. Here’s a quick chart to help you decide. You need temperature. You need wind. You need barometric pressure. If your working range exceeds 1000m then you probably should have humidity too.

https://docs.google.com/spreadsheet/pub?key=0AqxWm96xvM0fdGs1WEd5c2w2Mm5LNUg4dll5QXFRMGc&single=true&gid=0&output=html

Once you get your Kestrel start off by reading the manual and setting the elevation to zero so that you always get an absolute barometric pressure reading. This will make Ballistic_XLR and all other ballistics calculators treat you a lot better.

Now take that Kestrel outside and screw around a bit. Notice the difference between how wind moves across the ground compared to how it moves a few feet and several feet above the ground. See how being at the foot of a hill and the peak of a hill and in the trough of a valley affect your wind readings.

Now you have to come to terms with the fact that reading wind is an art and predicting the wind value correction you have to make for a really long range shot is something you learn to do with greater and greater precision by getting out and doing it.

I use a Kestrel 3500. It doesn’t do humidity but humidity doesn’t really matter enough to be that worried about. I have to adjust up a click or down a click if it’s desert conditions or almost raining respectively. So what I do is add a half click to my elevation and take the extra click if my solution lands at .03MRAD or more above an even number. So if my firing solution minus humidity says 10.33MRAD and I’m in the desert with ultra low humidity and I add that half a click I get 10.38 (10.33 + .05). If my firing solution says 10.31MRAD then adding the half click gets me 10.36 and I do not take the extra click. This is sort of like rounding except that my trigger number to round to the next click is 80% instead of 50%. The .03MRAD of slop that’s in there can be held or dialed or ignored depending on the range.

What about other brands? Sorry man. I found that in this case there are other instruments that are of the same quality but they’re of the same price too and since Kestrel have been adopted by the community it’s probably best if you blend. Then when you need one you can borrow it and know instantly how it works.

We’ll come back soon with Part 2.

BADEDS Pelican Kit.

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Here’s the ultimate in protection for my ballistics provisioning gear. BADEDS Pelican. The BADEDS kit in the base form comes with a Targus sleeve that contains an aluminum combo document-store/clipboard. That’s great for containing the data pages. In a pinch I would sometimes toss my kestrel and iPod Touch and IR thermometer in there too but they’d rattle around and I worried about damaging the more expensive bits of gadgetry. Apart from that the metal container gets pretty hot in the sun and electronics don’t appreciate being hot, especially those that are meant to measure things like temperature.

A Pelican 1085 is just about perfect for holding an 8.5×11″ set of printed data as well as a few gadgets. It’s slender enough to slide inside a backpack and takes care of delicate instruments a hell of a lot better than a drag bag. It’s bad enough we leave rifle scopes in a drag bag but electronics are even more delicate and need to be cared for.

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The whole idea of Ballistic_XLR is that we do use gadgets but we also need to be ready for when they break or batteries die. It doesn’t mean to avoid them. Nonetheless we need to take steps to keep them in functioning order. You never know how long and strained your supply lines might be.

In a Pelican case things are safe from water thanks to the rubber seal. They’re safe from being bashed around too thanks to fitted foam via their Pick-n-Pluck foam. There is also some substantial resistance to severe heat soak thanks to the insulating nature of the foam.

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The case may not appear to have much in it but really there’s everything there that I need to be able to engage targets at any range. My Kestrel and my IR thermometer are the gadgets in there that are most necessary to nailing those first round bulls-eye hits.

I regularly use KAC BulletFlight Military Edition on my iPod Touch. It’s actually slower to use than Ballistic_XLR because it doesn’t make MVV changes for you and it’s a bit tedious to set up a load in it in the first place but if I’m not being picky about where on the target I want to hit then it’s sufficient. The problem is that if you leave it in the sun for a few minutes on a nice warm day then it eventually heat soaks and shuts itself down. That’s a catastrophic failure because the data is not available from it anymore. This is exactly why Ballistic_XLR was created.

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Now when a gadget fails I’ve got a non-electronic way of getting my data. Ballistic_XLR is actually super fast to use too. I can address one element of adjustment at a time and run in a quick and precise scope adjustment or I can take more time and use the calc form with the data and nail the spot on the target I want to hit.

The Pelican case makes a decent writing platform and I don’t really need a proper clipboard thanks fitted foam cutout. What it all amounts to is a solid way to store, organize, transport, protect and use my extensive data provisioning supplies. All I need beyond that is a rifle and ammo.

Get your BADEDS kit today.

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