The M16A1 Build: Introduction

The M16 in use during The Vietnam War.
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Perhaps one of the most iconic weapons of war of all time. Glossy black plastic handguards, triangular front sight, distinctive carry handle…. The M16.

It was the rifle that has proven itself to be the pinnacle of modern weapons development and continues to be the current issue weapon for the United States, albeit in an updated form. For this reason I want to add an example of an original “retro” Vietnam era M16 to my firearms collection. But the path to fulfilling that goal is not as straight forward as it may initially seem. This article will explore my process of how I came to the solution to build a semi-automatic M16 replica. The article will also answer the question of why I chose not to buy one of the available reproductions on the market and act as a basic buyers guide to those considering a replica M16 for their own collection. Hopefully this article will help others navigate the world of the “Retro AR” while also serving as a starting point for the upcoming series of articles detailing my journey to build a replica M16A1.

Why not just buy an original M16?

First and foremost I should explain why I am not even considering purchasing an original M16A1. This deserves an explanation because the vast majority of my collection of weapons and equipment are original historical items rather than reproductions. I feel that original items inherently tell a better story of history than new made items. But I will make exceptions when an original item is too difficult to procure or downright too expensive.

The original M16 that young men carried in Vietnam was a select fire weapon, which means that you can select to fire single shots per trigger pull or unlimited shots for as long as the trigger was held down. In simple terms, the M16 is a machinegun. Owning an original full auto M16A1 is not possible for me due to the tremendous cost of legally registered machineguns in today’s market. For example, an original sold at the Morphy auction house in October of 2015 for $22,425.00, (not including tax and fees).* Buying a machinegun in the US also requires a $200 tax payment and a 9-13 month waiting period for the weapon to be transferred to your name by The Bureau of Alcohol, Tobacco, Firearms and Explosives, (commonly referred to as the ATF).

Needless to say the above excludes buying an original M16 because $23,000 is not what I consider “cost effective”. Also waiting a year or more to take possession of a rifle is not attractive- not to mention the various legal considerations that come with machinegun ownership. Luckily, there are several semi-automatic versions of the Vietnam era M16 which are much less expensive and easier to obtain. However, a semi-auto rifle is not an actual US Military issued M16 and will always be just a replica. There are three goals I usually keep in mind when adding any replica to my collection. These goals will act to guide my search for a M16 replica to add to my collection: A) use as mostly original military parts, B) be cost effective, and C) it should be visually identical to an original.

Photo credited as showing 4th Infantry Division soldiers upon a landing zone in Quang Ngai province, 1967.
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Semi-Auto Replicas

Interestingly, civilian ownership of semi-automatic versions of the AR platform go almost as far back as the military adoption of the system. Colt sold nearly identical versions of the M16 to the public during the Vietnam War generically referred to as the “AR-15 Sporter”. These vintage semi-auto versions of the military M16 are now generally referred to as the “SP1”. The SP1 looked very similar to the M16 but had some small differences in construction, as well as different markings on the receiver. An original Vietnam era SP1 would be as close as legally possible to owning a real M16. However vintage collectable SP1s are getting hard to find and exact a premium on the market. Retail pricing for an SP1 in today’s market can be observed in an example that sold for $2,300 in the Rock Island December of 2019 auction.** The SP1 is an ideal stand-in for an original M16 due to it’s historical value. Unfortunately at this time over $2,000 is beyond my budget for this project at this time.

A vintage Colt advertisement for their “AR-15 Sporter”, now colloquially known to collectors as the SP1.
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As a relevant side note, Colt continues to make semi-auto M16 style rifles for the civilian market. In 2017 at SHOT show Colt revealed a new production M16A1 style rifle called the “M16A1 Retro Re-Issue”. High quality fit and finish coupled with identical markings to the original makes the Colt Retro Reissue is the best reproduction M16A1 on the market. But the Colt Reissue is just as expensive as an original SP1 with the retail price being $2500. Considering the other options available; the options from Colt are out of my price range.

Another modern candidate for a semi-auto M16 comes from Brownell’s, Inc.*** At SHOT show 2018, Brownell’s unveiled a new line of complete “Retro” rifles for sale. The release featured the complete lineage of the M16/AR-15 development from the very first prototypes of the M16 design to the M16A1. I remember being excited about the Brownell’s “Retro” line of rifles when the first footage from the SHOT show release hit my YouTube feed. The Retro rifles were very affordable compared to the Colt Reissue costing $1,300 for a complete rifle. Unfortunately after two years the “retro” line of rifles has been sold-out. This may be best because the Brownells Retro line falls short of two of my three goals; they use no original parts, and their finish details were not quite the same as original rifles to keep cost down. The “Retro” rifles featured anodized black finish where the original M16 had a distinctive dark grey, the furniture was matte black and looked different than the iconic glossy plastic of the originals, and the lower receivers were marked with modern engraved markings that were very different than the stamped “roll markings” of the originals. While the Brownells rifles were half the cost of an SP1, and reportedly mechanically excellent rifles- they still fall short of my requirements.

The Brownells M16A1 Replica. Note the black anodized color, the matte furniture and the modern engraved markings.
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Building a Replica From Scratch

The final option that was available to me was to build a semi-auto M16 replica using parts from a vintage military parts kit. Building a replica using original parts can be the cheapest and most historically accurate option. It can also be the most difficult; requiring gunsmithing tools, skills, and patience.

For years I have been an avid admirer of vintage retro M16 builds on, as well as the r/RetroAR page on These are communities of folks who collect vintage AR-15 variants and often have to piece their semi-auto replicas together from original parts. I am not a total stranger to building an AR-15 from parts but I have never done a build as complete as ordering a parts kit and starting from the ground up.

Key to the project would be an original M16 military parts kit. To explain what a parts kit is: they are a disassembled firearm which has had certain elements removed. Considering guns like the M16, the only way to import machinegun components into the United States is via parts kit. The ATF regulates that parts kits cannot be imported with certain key components to avoid easy illegal manufacture of machineguns. In an M16 parts kit the excluded parts are: receiver, barrel, and auto sear. To make a semi-auto replica I would need to source a new barrel, and semi-auto lower receiver.

Despite the exclusions, a parts kit means I could have as a historically accurate example made with original parts as the law and my pocketbook would allow. Buying the parts and assembling them could potentially come together for around $1000 which is even cheaper than a Brownells rifle.

The final reason I am most interested in a building a replica is that I enjoy building things from scratch and the process would make the rifle special to me. By taking control of nearly every aspect of the build process I can also pay attention to every detail and the end product can be virtually identical to a Vietnam issue M16 minus the auto sear while being the most cost effective option available.

People know know me best can say I rarely choose the easiest route to a solution. But building a retro M16 replica will have unexpected joys. During a time where the majority of us are still in lockdown due to COVID-19 a project like this is an excellent way to engage with this history. Besides: can there be a better way to learn about the weapon young in carried in Vietnam, other than by building one from the ground up?


A Special Forces Captain demonstrates firing an early Colt 601 one of the earliest versions of the AR-15 adopted for military issue that predated the M16. Note the “three prong” flash hider, chrome bolt, and “slab side” lower receiver.
Source: Life Photo Archive by


*Morphy’s remains one of the premier collector firearms auction houses in the US. They are very reputable in high-end machinegun sales:

**Rock Island Auction House is another reputable firearms auction house that specializes in collector grade firearms. (The auction house has no affiliation with the Rock Island Arsenal)

***Brownells Inc. is one of the leading firearm supplies and parts suppliers in the world.

Colt M16A1 Reissue: Retro Rifles Discussion Page: r/RetroAR Discussion page:

Published by ModMilHistAdmin

My name is Andrew and I am deeply passionate about military history. Throughout my journey engaging with history I have cemented an opinion that education is power, and that an educated society leads to progress. I firmly believe that if more people engaged with military history and understood the reality of conflict, than our society would be more eager to exhaust all peaceful options before engaging in armed conflict. In this regard, I am compelled to share my journey with respect, integrity, honesty and a touch of humor with the hope that some people will learn about our tumultuous past and therefore decide to strive for better moving forwards into this century.

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