SDI: Extreme AR Accurizing

Most don’t think of AR’s when it comes to precision rifle builds. Rick Casner from the Sonoran Desert Institute joined us to explore AR accurizing. 


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General AR Technology and Gunsmithing 

AR’s are incredibly popular. Many people build their own and there are nearly endless accessories for them. It can be hard to differentiate yourself as an AR builder, but it’s always prudent to start with the basics. Gunsmithing fundamentals are the same no matter what platform you’re working on. 

Understanding how a firearm functions is a great place to start. In the AR world, you have piston driven and the direct impingement system (which some argue is also piston driven). The cycle of operations includes eight steps: feeding, chambering, locking, firing, unlocking, extracting, ejecting, and cocking. These eight steps happen in every firearm, but it’s important to look at exactly how each step takes place in gas-operated and blowback operated guns. 

AR-specific tools are another concern. While you can use a wide variety of equipment, there are some tools specifically designed for working on AR’s to prevent damage. Cleaning nuances exist as well. 

When you’re building an AR, you need to think about headspace, buffer weights, springs, gas blocks, gas tube lengths and gas port diameter. All of these things can be fine-tuned and may need to be, especially if you are running a suppressor. 

The bolt itself is kind of a piston in this platform, and deserves its own attention. Some parts are interchangeable and some coatings are better than others. If there’s something you want, somebody makes it. 

Departing from the traditional AR, you also have PCCs like the CMMG Dissent, which is a bufferless design, and the CMMG 9mm Banshee with radial delay blowback. These types of systems make feeding more reliable in the PCC platform. 

Shooting the CMMG Radial Blowback AR


About SDI


Sonoran Desert Institute is a DEAC accredited, online school that helps students learn the skills and techniques they’ll need to be successful in the firearms and unmanned technology industries. SDI’s faculty is comprised of professionals with decades of industry experience, and our programs are designed to combine modern learning methods, hands-on training options, and the flexibility of online education.

Sonoran Desert Institute was founded in 2000, and was approved for training by the Arizona State Board for Private Postsecondary Education in 2001. The Institute was accredited in 2004 by the Distance Education Accrediting Commission (DEAC). The DEAC is listed by the United States Department of Education as a recognized institutional accrediting agency for distance education. The DEAC is also recognized by the Council for Higher Education Accreditation (CHEA).

At its inception, the Institute offered Gunsmithing as a program, which ultimately became the foundation for SDI’s growth. Key to the success of the Institute is its comprehensive approach to easily understood curriculum, attention to providing quality service to its students, and the flexibility of its instructional model.

In 2012, Sonoran Desert Institute was acquired by the Trade Training Company, LLC. This transfer was approved by DEAC and the Arizona State Board for Private Postsecondary Education. In 2014, SDI introduced armorer courses as part of its programs.

Also in 2014, SDI applied to DEAC for Title IV Certification. In 2015, after receiving approval from DEAC, the institute submitted its application to the U.S. Department of Education (ED) to offer Pell Grants and Direct Loans to students in the Associate of Science in Firearms Technology. This change was primarily prompted by the Department of Defense’s regulatory change linking eligibility for Active Duty Tuition Assistance to schools approved for Title IV funding. Recognizing the high percentage of military students in our student population, SDI deemed this as an important initiative. SDI began offering Title IV funding to students in January 2016. In January 2018, after receiving approval from Department of Education, SDI also began offering Title IV funding to students in the certificate program.

In June 2018, SDI was granted a 5-year renewal of accreditation and in fall of 2018, SDI transitioned to become an employee owned company (ESOP). SDI takes pride in upholding the standards of multiple regulatory bodies while continuing a student-centric focus on academic quality and superior service to students!

In January 2022, SDI introduced the School of Unmanned Technology and began to offer the Certificate in Unmanned Technology – Aerial Systems program.

SDI Modern Sporting Rifle Course

Lapping the Bolt Lugs

SDI offers a  Modern Sporting Rifle (MSR) course covering the most popular AR platforms including the AR-9, AR-15, AR-10/LR-10. They cover the evolution of the AR platform, cycle of operations, operating systems, various components in each platform, buffer types and barrel lengths, measuring devices and tools, headspace and twist rate, general assembly, firing pin protrusion, function check and dimpling a barrel. An important point to note is many believe they are fully familiar with all these concepts, but they generally are familiar as an operator, not as a gunsmith. Function checks, for example, doesn’t just mean, “does it go bang?”. Function checking for a gunsmith includes looking for potential future malfunctions. 

Taking the Next Steps 

In general, off the shelf AR’s are just put together. I was curious about how you could accurize an AR and so consulted my gunsmithing partner and mentor, Gordy Gritters.

Slugging the Barrel

Gordy did a number of extreme AR builds in the late 90s and more recently incorporated the platform into his course offerings. There are many considerations when accurizing an AR and a lot of opportunity for gunsmiths. We filmed a full program covering the process in the works!

With factory Hornady match ammunition, our efforts took a CMMG Endeavor  from a ⅞ MOA gun to a ⅜ MOA gun (with our limited testing).


Truly understanding a firearms system allows you to better diagnose and fix problems as well as make improvements. Focusing on the AR platform, specifically on accurizing, opens a world of opportunity for gunsmiths. 

Facing an AR Upper on the Lathe

Contact SDI online:

Or by phone: 480-999-4767

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Gavin Gear

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