AR owners know that their black rifles require regular cleaning and maintenance. And this modular platform allows many options for stocks, fore-arms, and optics mounting. That ability to customize is one of the AR’s major attractions, but customization requires solid understanding of the AR’s design and components.
To help AR owners optimize and maintain their rifles, Gun Digest Media has a 320-page illustrated book: AR-15 Setup, Maintenance and Repair. Authored by Patrick Sweeney, this paperback book is a “one-stop guide to repairing, maintaining and modifying America’s favorite rifle.” The current price for the book is $29.99 from Gun Digest, or $32.34 on Amazon. Gun Digest also offers a $29.99 Digital Download version.
GET FREE 40-Page AR-15 Book Sample
Note, if you are interested in the book, there is a substantial 40+ page FREE sample available on the Amazon site. You can see the entirety of the first two chapters from the Kindle digital version. CLICK HERE to visit Amazon.com and then click on the button labeled “Read Sample” below the cover image.
AR Set-Up and Maintenance
If you need to disassemble and maintain your AR rifle, swap barrels or handguards, add optics, or customize the stock, Gun Digest’s AR-15 Setup, Maintenance and Repair book tells you what you need to know. From field-stripping to barrel mounting and trigger installations, the book covers a wide range of topics. The book provides step-by-step instructions for set-up and maintenance, with hundreds of detailed photos. The book also includes AR gunsmithing chapters with reviews of recommended tools.
Author Patrick Sweeney is a certified master gunsmith and armorer instructor for police departments. Sweeney has also authored the notable 4-volume Gunsmithing the AR-15 series (Vol. 1, Vol. 2, Vol. 3, and Vol. 4) and 20+ other titles for Gun Digest Books.
Whether you want to learn about disassembling your AR for regular maintenance, field-stripping, swapping out parts, adding optics or customizing a stock, AR-15 Setup, Maintenance and Repair guides you through everything you need to know to keep your AR-platform rifle running well. There are also tips on how to improve accuracy, and maintain your bolt carrier group properly.
Authored by Patrick Sweeney
Published by Gun Digest Books
ISBN-13: 978-1951115470
320 pages, softcover, 8 ¼ x 10 7/8 inches
Editor’s NOTE: The key to keeping an AR running reliably is proper lubrication (in the RIGHT places), and regular cleaning of the bolt carrier and bolt, including ejector recess and extractor recess. The majority of non-functioning ARs we’ve seen had gunk, lube, carbon, and brass shavings in those recesses.
Other AR Books by Patrick Sweeney
Bonus Video — AR15 Maintenance with Jerry Miculek
In this helpful video, legendary shooting Jerry Miculek explains how he cleans and maintains his AR-platform rifles. Miculek shoots ARs in three-gun competitions.
“A bullet launched at a higher altitude is able to fly slightly farther (in the thinner air) for every increment of downward movement. Effectively, the bullet behaves as if it has a higher ballistic coefficient.”
A few seasons back a good friend ventured to the high country of Colorado to pursue elk. He recently zeroed his rifle in California, at a range just a few hundred feet Above Mean Sea Level (AMSL). He wondered if the higher altitude in Colorado could alter his ballistics. The answer is a definite yes. However the good news is that free ballistics calculators can help you plot reliable drop charts for various shooting locations, high or low.
The question has been posed: “What effect does altitude have on the flight of a bullet?” The simplistic answer is that, at higher altitudes, the air is thinner (lower density), so there is less drag on the bullet. This means that the amount of bullet drop is less at any given flight distance from the muzzle. Since the force of gravity is essentially constant on the earth’s surface (for practical purposes), the bullet’s downward acceleration doesn’t change, but a bullet launched at a higher altitude is able to fly slightly farther (in the thinner air) for every increment of downward movement. Effectively, at higher altitudes, the bullet behaves as if it has a higher ballistic coefficient.
Forum member Milanuk explains that the key factor is not altitude, but rather air pressure. Milanuk writes:
“In basic terms, as your altitude increases, the density of the air the bullet must travel through decreases, thereby reducing the drag on the bullet. Generally, the higher the altitude, the less the bullet will drop. For example, I shoot at a couple ranges here in the Pacific Northwest. Both are at 1000′ AMSL (Above Mean Sea Level) or less. I’ll need about 29-30 MOA to get from 100 yards to 1000 yards with a Berger 155gr VLD at 2960 fps. By contrast, in Raton, NM, located at 6600′ AMSL, I’ll only need about 24-25 MOA to do the same. That’s a significant difference.
Note that it is the barometric pressure that really matters, not simply the nominal altitude. The barometric pressure will indicate the reduced pressure from a higher altitude, but it will also show you the pressure changes as a front moves in, etc. which can play havoc w/ your calculated come-ups. Most altimeters are simply barometers that read in feet instead of inches of mercury.”
As Milanuk states, it is NOT altitude per se, but the LOCAL barometric pressure (sometimes called “station pressure”) that is key. The two atmospheric conditions that most effect bullet flight are air temperature, and barometric pressure. Normally, humidity has a negligible effect. It’s important to remember that the barometric pressure reported on the radio (or internet) may be stated as a sea level equivalency. So in Denver (at 6,000 feet AMSL), if the local pressure is 24″, the radio will report the barometric pressure to be 30″. If you do high altitude shooting at long range, bring along a Kestrel, or remember to mentally correct the radio station’s pressure, by 1″ per 1,000 feet.
Trajectory of Bullet fired at Sea Level
Trajectory of Bullet fired at 20,000 feet
You can do your own experimental calculations using JBM Online Ballistics (free to use). Here is an extreme example, with two printouts (generated with Point Blank software), one showing bullet trajectory at sea level (0′ altitude) and one at 20,000 feet. For demonstration sake, we assigned a low 0.2 BC to the bullet, with a velocity of 3000 fps.
To learn more about all aspects of Exterior Ballistics, Hornady has a useful discussion of External Ballistics including the effects of altitude and temperature. To dig deeper, Sierra Bullets has a comprehensive Exterior Ballistics Resource Page with multiple sections from the Sierra Manual (4th and 5th Editions), including:
Example from Section 3.0: “When a bullet flies through the air, two types of forces act on the bullet to determine its path (trajectory) through the air. The first is gravitational force; the other is aerodynamics. Several kinds of aerodynamic forces act on a bullet: drag, lift, side forces, Magnus force, spin damping force, pitch damping force, and Magnus cross force. The most important of these aerodynamic forces is drag. All the others are very small in comparison when the bullet is spin-stabilized.”
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Larry Medler has devised a smart little invention — a simple, inexpensive Empty Chamber Indicator for rimfire rifles. It is made from a section of plastic “weed-wacker” line and a wooden ball from a hobby shop. Larry says he was inspired by Juniors who used something similar for their 17-Caliber Air Rifles.
How to Make the Empty Chamber Indicator
Construction Method: First, drill a 7/64″ diameter hole all the way through the 1″-diameter wooden ball. Then enlarge half of that 1″-long hole using a 13/64” diameter drill. Next insert an 8″ piece of heavy duty (0.095″ diameter) weed wacker line through the ball, leaving about 2″ on the side with the bigger-diameter hole. Then, with the short end of the line, fold over the last half-inch so the line is doubled-over on itself. Then slide the line into the ball, stuffing the doubled-over section through the 13/64″ (large) hole. Finally, pull the longer end of the line until the doubled-over section is flush with the outside of the ball. This gives you a sturdy line attachment without messy adhesives. When the assembly’s complete, hold the ECI by the tail and dip the ball in yellow paint. If you’re making more than one ECI, you can drill horizontal holes in a spare block of wood and use that as a drying rack.
At a Rimfire Sporter match like this, all shooters must have an Empty Chamber Indicator.
The Empty Chamber Indicator for Smallbore Rifles
Larry explains: “At all Highpower rifle matches, silhouette matches, and other shooting events I have attended, Open Bore Indicators (OBI), or what are now called Empty Chamber Indicators (ECI) have been mandatory. The NRA’s yellow ECI for Highpower rifles is easy to use and has been well-received by the shooters. However, I had not seen a truly workable ECI for 22 rimfire rifles — until I visited Michigan’s Washtenaw Sportsman’s Club where I saw juniors using ECIs for their 17 Caliber Air Rifles. Someone at the club made the empty chamber indicators by attaching an 8″ piece of weed wacker line to a 1″-diameter wooden ball, painted bright yellow. I now make similar ECIs for the 22 rimfire silhouette matches I run.”
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AR Set-Up and Maintenance
The question has been posed: “What effect does altitude have on the flight of a bullet?” The simplistic answer is that, at higher altitudes, the air is thinner (lower density), so there is less drag on the bullet. This means that the amount of bullet drop is less at any given flight distance from the muzzle. Since the force of gravity is essentially constant on the earth’s surface (for practical purposes), the bullet’s downward acceleration doesn’t change, but a bullet launched at a higher altitude is able to fly slightly farther (in the thinner air) for every increment of downward movement. Effectively, at higher altitudes, the bullet behaves as if it has a higher ballistic coefficient.
