ADBR PLUS 5.56 - You asked and we listened! During several conversations with ATAC Defense dealers and customers we kept getting the same question. "Can we get nickel boron bolts and oversized charging handles for the basic rifle?” We heard your request, and the Basic Plus was born. This rifle has all the features of the "not so basic rifle", but upgraded with the nickel boron bolt and oversized charging handle.
At ATAC Defense: quality, reliability, accuracy and fit/finish are our greatest concerns.
We believe in holding a quality level that is far above "mil-spec".
All of our components are handpicked and tested by the marksmen that design our rifles.
Our upper and lower receivers are machined "in-house". We perform this critical task ourselves so we can insure proper fitment, without slack and rattle.
Each ATAC Defense firearm is hand assembled with our inspected, tested and approved components.
After assembly, each firearm goes through a test fire session and is re-inspected. Each firearm must pass our final inspection before it can be shipped to the customer.
This product can only be shipped to a valid FFL holder.
When ordering, please enter your FFL's address into the shipping field. Include their contact email or phone number in the notes field so we can exchange FFL's.
ATAC Defense Lower Receiver:
Our lower receiver starts as 7075 T6 aluminum forging that is final machined to our exact tolerances. Our internal tolerances exceed the mil-spec tolerances for a lower receiver. After inspection, it moves through our in-house magwell broaching process to ensure proper dimensions, and a straight/true magwell. After broaching the lower goes through a vibratory tumbler that utilized ceramic media to deburr the lower. Our lowers are continuously inspected during each step in our process, after tumbling it goes through one more final inspection to insure our quality standards. After passing all inspections, each lower receiver is laser engraved with ambidextrous bullet markings, and ATAC Defense information. Additional, enhanced features of our lower include: threaded bolt catch pin, threaded (captured) rear detent pin and a upper to lower adjustment feature.
ATAC Defense Upper Receiver:
Our upper receiver also starts as a 7075 T6 aluminum forging that is machined to exacting tolerances at standards higher than mil-spec. It also has to pass inspection at every machining station that it goes through. It then is tumbled and deburred in a vibratory tumbler using ceramic media. After this point it goes through a final inspection to make sure that it meets the standards we require for our rifle builds. During the machining process we choose to leave the upper receiver lugs slightly over-sized. Utilizing the over-sized lugs, we hand fit each upper and lower receiver to insure a proper tight upper/lower fit without slack or rattle.
ATAC Defense Barrel:
Our M4 contour 4150 CrMoV barrel starts life as a true gun barrel steel blank per *Mil-B-1159SE
*MIL-B-11595E, MILITARY SPECIFICATION: BAR, METAL AND BLANKS, STEEL (UNDER 2 INCHES IN DIAMETER) FOR BARRELS OF SMALL ARMS WEAPONS. This specification covers alloys steel, bars and blanks under 2 inches in diameter for use in the manufacture of barrels for small arms weapon.
All ATAC Defense barrels are precision bored and button rifled using a 6 groove rifling at a 1:7 twist rate. Each chamber is cut to match the 5.56 caliber. After boring, rifling and chambering, the exterior of the barrel is cut to the M4 profile with a .750 gas block diameter, and a 1/2 x 28 muzzle thread. The gas port is properly sized to achieve the right gas pressure for proper ejection.
After final machining, inspection, and testing the barrel is then coated and quenched to provide a durable lasting finish. At assembly an A2 flash hider is mated to the 1/2 x 28 threaded barrel.
ATAC Defense Bolt and Carrier Group: Our bolts are precision machined from *Carpenter 158 steel.
*Carpenter No. 158® alloy is a chrome-nickel alloy steel with an analysis representing the best case hardening steel known for parts subject to heavy shock and wear. This alloy is ideally suited for jobs where an extra measure of core strength is required. Fully treated, Carpenter No. 158 alloy attains a core strength of approximately 160 ksi (1103 MPa) tensile strength with a yield point of approximately 135 ksi (931 MPa). These high mechanical properties will be developed in sections up to 5" (127 mm) thick. In addition, case hardened articles possess a higher wear resistant case because of the special alloy content of the steel. Specifications: AMS 6265, ASTM A646, QQ-S-624C, SAE J1249
After machining the bolt is vibratory tumbled and deburred. It is then subject to *MPI (magnetic particle inspection) also known as MP to prove that the bolt has no defects or flaws.
*Magnetic particle Inspection (MPI) is a non-destructive testing (NDT) process for detecting surface and shallow subsurface discontinuities in ferromagnetic materials such as iron, nickel, cobalt, and some of their alloys. The process puts a magnetic field into the part. The piece can be magnetized by direct or indirect magnetization. Direct magnetization occurs when the electric current is passed through the test object and a magnetic field is formed in the material. Indirect magnetization occurs when no electric current is passed through the test object, but a magnetic field is applied from an outside source. The magnetic lines of force are perpendicular to the direction of the electric current, which may be either alternating current (AC) or some form of direct current (DC) (rectified AC). The presence of a surface or subsurface discontinuity in the material allows the magnetic flux to leak, since air cannot support as much magnetic field per unit volume as metals.To identify a leak, ferrous particles, either dry or in a wet suspension, are applied to a part. These are attracted to an area of flux leakage and form what is known as an indication, which is evaluated to determine its nature, cause, and course of action, if any.
The carrier is machined from *AISI 8620 alloy steel to full auto profile, then stress relieved, and case hardened (carburized).
*AISI 8620 is a hardenable chromium, molybdenum, nickel low alloy steel often used for carburizing to develop a case-hardened part. This case-hardening will result in excellent wear characteristics.
The gas key is machined from 4130 chromoly alloy, heat treated, and attached to the bcg using grade 8 hardware torqued to the recommended spec. After the bolts are torqued they are properly staked to mil-specifications.
The bolt carrier group is assembled using stainless steel gas rings, a 4340 heat treated cam pin, and an 8640 heat treated firing pin. The extractor is heat treated precision ground 4340, and a S7 heat treated ejector is used.
For bolt coatings the Atac Defense Enhanced Rifle uses nickel boron or hard chrome coatings to provide easy cleanup and long lasting performance.
ATAC Defense Gas System:
We use a precision machined 4140 steel .750 diameter low profile gas block. The gas block is mated to a 304 stainless steel carbine or mid length gas tube.
We utilize a 7075 6 position receiver extension tube (buffer tube). We also use a mil-spec end plate and castle nut. During assembly the castle nut is torqued and staked. A mil-spec stock is then mated with the receiver extension.
Charging Handle: Our ambidextrous oversized charging handle is machined from 6061 T6 aluminum. We chose this handle specifically to make charging the firearm faster and easier, even with optics.
Buffer and Spring:
A standard 3oz weighted buffer and mil-spec spring are used.
Our free float handguards are machined from 6061 aluminum. They are then tumbled and deburred. They feature m-loc attachment points on both version 1 and 2.
Lower Parts Kit:
Each ATAC Defense basic rifle utilizes a Mil-spec lower parts kit. Mil-spec parts kits have stood the test of time and are known for reliability and toughness.
Recoil Review on the ADER version of our rifle: