Constructing and Gunsmithing the AR15 and M16 Type Rifles


One of the most popular ways for survivors to express their independence and gain familiarity with their primary rifle is to build it themselves.  Home manufacture not only gives the survivor the satisfaction that comes with the pride of building something, but it can save money. 

Another reason for standardization of the AR15 type system is the remarkable utility you get by switching sub assemblies to make different weapon configurations.   You can, in theory have only AR15 type guns as long guns for a survival arsenal, with different configurations serving different roles.  By standardizing your groups parts, supplies and Gunsmithing expertise with this weapon system, you have access to almost every major type of firearm from a .22 plinker, a big caliber sniper rifle, an assault rifle to a 9mm subgun.  

This excellent set is made up of a registered class 3 lower receiver with upper receiver assemblies set up in three common calibers.  The set gives the owner several weapon configurations on one system.   The legal ownership of the select fire lower makes it possible to secretly get or make full automatic lowers for the rest of the uppers while enjoying legal shooting in the 3 calibers and training with the different configurations.   The upper receiver assemblies which are necessary for the caliber change are not a heavily restricted item in the US.   The lowers are another story, thus it is fairly common for collectors to have more than one upper for each lower assembly, especially if one has a long barrel and the other has a short barrel.   Note that there are legal issues to contend with if you have in your possession a barrel under 16" and no class 3 lower or legitimate AR type pistol.    Prosecutions for "constructive possession" of a short barreled rifle against those with the popular short barrels and a semi-automatic AR15 have not always been successful. 

One element of the cost of a gun is a federal tax that the manufacturers pay before the gun ever leaves the factory.  This tax usually represents 10% of the price that the manufacturer charges the first line buyer (usually a distributor).  In the case of a decent AR 15 clone that can range from $65 to $100 in cost that eventually gets passed on  to the buyer.   

Another element of cost in the rifle is dealer markup.  If a dealer has to invest in $700 to $2000, he is going to expect to make a reasonable profit on the transaction that is appropriate to the value of the merchandise he handle.  Likewise, state sales tax will be charged on the basis of the value of what you purchase through the dealer.   Sales tax alone can account for another $50 to $150 of the price of the rifle.   In many restrictive states and countries, additional money is factored in as profit for smugglers and contraband dealers.  

An AR15 type rifle is made up of two major components, the lower receiver assembly and the upper receiver assembly.  It is the lower that is typically regulated and the upper that almost anybody can purchase from a parts seller in the US with little or no paperwork.  Many of the other parts are also restricted in other countries.  For example, England restricts the barrels, but not the lower receivers.  German laws mimic UK laws on this.   French law restricts some barrels but not others based on whether or not they are chambered for a military caliber.   Israel does not restrict the guns or parts much, (for citizens) but does tightly restrict ammunition, magazines and the total number of guns a person may own.  

So what we end up with is an average of $200 of the cost of an AR15 is taken up in commerce based taxes which add no real value to the gun.  As far as the government is concerned, the legally restricted part of the rifle (in the US) is the receiver.   Taxes are based on the value of the receiver and all parts that are attached to it at the time of original retail sale.  This means that the only part the original buyer is legally obligated to buy through a licensed dealer is the receiver.  This part typically costs $85 to $150 retail for a current production sample with no other parts attached.   With the rest of the parts attached, this runs from $150 to $350.   In some cases, receivers made before the 1994 assault weapons ban will sell for considerably more.   This is not because they were built any better, but because of the implied license to use one to build an AR15 type rifle in configurations that would not be legal for a "post-ban" gun. 

Upper assemblies and their component parts can be legally and easily purchased from any number of sources.  They vary in features and quality, but a decent quality assembly like this one from Bushmaster can be had for around $500.  

Lowers can be purchased by most FFL holders in the US and in parts of Canada.  A "stripped" lower is the cheapest way to go in order to save sales taxes and dealer markups, but you might also want to consider buying a "completed" lower with all of the internal parts and stock installed.  This will minimize the Gunsmithing work involved in building the rifle to simple assembly.  

As a last resort, the survivor can manufacture a receiver from scratch or a partially finished casting.   While some very high quality receivers have been made from scratch, these almost always have been done with technically advanced computer aided machinery.  This is beyond the ability of most home shops.  A tolerable option is to finish a partially manufactured receiver.  This is usually one that has been made from a raw aluminum casting and around half to 80% (the legal limit) of the machine work done.  One of the better sellers of these partially complete castings is the Tannery Shop.   (click here for a link to their website).   The Tannery lowers require a fair amount of metal work to complete and they cost only slightly less than commonly available completed receivers from regular gun shops and parts suppliers.  The difference is in the lack of paperwork required to purchase the Tannery lower.  A major part of the cost involved with finishing a Tannery lower is the purchase and or rental of special tools and or drilling jigs.   The finishing and construction cost of rifles based on the tannery lower is often a matter of the economy of scale.  The lowers tend to cost $90 each, while specialized drill bits, taps and reamers can run another $200.  Obviously not very cost effective if you can obtain a factory made lower receiver at a gunshop for $200 including tax and the assurance that the specifications are right.  It is common for home builders to make errors when finishing the Tannery lowers.  In many cases, these errors can be corrected by a variety of methods, but the quality of the finished product is often below that of a factory lower.   That is not to say that a gun based on a home-built lower is going to perform badly, as final performance is largely a function of how much tweaking and finishing a gunsmith will put into the project.  There are plenty of guns based on factory built lowers that will not perform as well as a gun based on a Tannery lower. 

Click here for the most up to date information on using the new style jig

Click here for information on where to get 80% castings for the AR15, 1911 and other guns

Special notes on full auto conversion and use of the jig for M16 milling and drilling. 

Other receiver modifications

Finishing the receiver is deceptively complex.  Several cuts must meet critical tolerances to ensure that the gun will work right.   Several hobbyist survivors have come up with different methods for finishing the receiver.  The traditional method is to use machine tools like a milling machine and maybe a drill press.  Some people have improvised and adapted some of the tolerances and parts to reduce the need for these costly tools.  In a worst case scenario, the part can be finished with a hand drill and the appropriate drill bits along with a collection of files and high grade epoxy.   One of the best methods is to make, buy, rent or borrow a specialized jig that aids in aligning some basic tools to do the job with a high degree of precision.  

 Click here for information on the OSI drilling fixtures. 

One issue of discussion and contention on finishing the lower is what type of coating or finish is best for the bare aluminum.  The metal is rather soft and extremely vulnerable to damage and wear.   The most highly recommended finishes are epoxy based resins and chemically applied finishes that cure as hard and durable as possible.   Even after finishing, it might be a smart move to paint the lower with some durable spray paint to seal in the finish.   I have my doubts as to the long term durability of the Tannery lowers, but considering the low cost and ready availability, they represent a decent option for survivors who may not have that many options or are putting together an arsenal that is strictly for shorter term survival.  It is probable that the receiver of a gun based on a tannery shop lower could be replaced by one cannibalized from a captured or damaged rifle later on.  It is conceivable that such a rifle could last a long time, but it will require a little more careful handling than a full factory built counterpart.  It is also several steps better than a wholly improvised gun or sporting gun that is simply not built with the features of a military weapon.  An advantage of the AR15 design over other guns is that the lower receiver does not have the highly critical tolerances that are inherent in other designs.   The main reason for this is that safety related issues like head spacing are a function of the fit between the bolt head and the barrel extension - two parts almost exclusively made in well equipped manufacturing facilities and made available on the open market with few restrictions. 

The primary differences between a select fire M16 receiver and a semi-automatic AR15 receiver is that the select fire receiver has some extra material removed and a hole drilled for an additional pin running through the trigger housing.   The extra pin holds the auto sear in place.  A semi-auto receiver is not set up to fit an auto sear.   Regardless of what unqualified people may tell you, a conversion to select fire requires the replacement of several parts and delicate machine work on the lower receiver.   A more popular method of conversion is to use removable components that act as a sear.  One is the DIAS, or drop in auto sear and the other is the lightning link.  Both are engineered to be temporary and used with no cutting or modification of the lower receiver, but they still require the substitution of several parts. 

Given that you have either made or obtained a lower receiver, the next step is to assemble the parts of the lower receiver.  This section will contain a sequence of pictures in the future that will illustrate and explain the full process.  Until then, it is best to purchase a Gunsmithing or armorer's  manual from one of the businesses that sells AR15 parts.  Most of your questions can be answered in the forum that is dedicated to building AR15 type rifles.  Click here to co direct to the forum.  

Another excellent forum I found for home gunsmiths is at Roder Custom.  You can go direct to their forum by clicking here.  

Note, the page below came from a discussion on one of the forums in response to a request for information regarding gas pressure problems in short AR barrels.  The consensus being that they are usually solved by removing the front sight tower/gas block assembly, drilling the gas port in the barrel larger (up to .090) and reinstalling the gas block.  This will often produce problems with overpressure in the gas system and unusually high cyclic rates and or sharper recoil on ARs with collapsible stocks.  

Information on short barrel gas system fixes


People have been having problems with AR15 type rifles with barrels shorter than the Military M4 (14" length) although the shorter barrels are commonly available.  The most common problems relate to reliability problems.  One expert on the subject had posted a very good essay on solutions to the problems and I have copied it to this page. 

The 11.5” barrel was used by the US Army on the XM-177. The M4 carbine later superseded this rifle. The 11.5” AR is a finicky animal. Sure some particular rifles will work in the semi-auto mode, but they are not reliable enough in full auto. This lack of reliability and its reduction in muzzle velocity did the XM-177 in.

The inherent problem with this set up that the gas port is to close to the muzzle. The AR-15 runs on the direct gas impingement system. Whereas a long stroke gas piston will work with the port close to the muzzle, the direct gas impingement system will not achieve reliability that is acceptable in military conditions, with the port close to the muzzle. The direct gas impingement system runs on the pressure behind the bullet after the bullet passed the gas port and before it exits. The Marines (US Army did not fund it for length of the program) funded the XM-4 program in order to get a more reliable shorty. It was found that the AR-15 needs at least four inches between the gas port and muzzle. This was determined after extensive testing. You will note that the 14.5” barreled M4 and the 20” M16 have the same distance form the port to muzzle.

Many AR-15 barrel makers and gunsmiths will attempt to correct this problem by drilling the gas port larger. This will result in increased bolt velocity. The bolt velocity achieved in current AR-15 type rifles is already faster then Stoner had intended. With increased bolt velocity in the AR-15 the extractor can skip the rim or rip it off. If the case is indeed extracted form the chamber intact, then problems can show elsewhere. The bolt will rebound heavily off the rear of the buffer tube and can come back over the mag before another round is stripped out of the mag. Once the bolt group strikes the barrel extension it will rebound farther back due to increased velocity and momentum. This can lead to the hammer falling while the bolt is unlocked. Normally this will simply show up as a miss fire in case of the later rebounding problem.

In short the problem is not port pressure that can be solved by port size. It is a time problem. Some reliability can be gained by using a heavier buffer. The M4 has been improved with the addition of the “H” marked buffer. With the larger port that is common on an 11.5” barrel the bolt group will be pushed hard for a short time. The heavier buffer can slow the bolt group down. A proper heavy buffer will also help in holding down bolt group rebound by absorbing some of the momentum. A better solution to using a heavier buffer is to use a standard length buffer tube/stock assembly. This will also reduce bolt velocity and corresponding bounce back.

I recommend simply replacing the barrel with one that locates the gas port farther away from the muzzle. Buy one that is Mil-Spec as in FN, Colt’s or Bushmaster. These barrels have chambers that are cut appropriately for use in an AR-15. The chamber dimensions in any gas gun are very important for reliable function. It would seem that your gas port is too large for a heavy buffer to fix. You could try a full size butt stock as a cheaper test.



This X-ray view of the internal workings of a semi-automatic AR15 should give you some idea of the details of its workings.   In this picture, you can tell that the hammer is cocked and the magazine is empty.  The light shaded areas are aluminum and the darker areas are steel.  






Sources of parts, tools and parts kits are listed here.

American Spirit Arms: For everything from parts to complete guns, ASA has it all at reasonable prices.  Customer service is better than average, pricing is good, quality on average with the reputable parts suppliers.  You can hop to their site with this link.  If you happen to order from them, let them know you heard about them from

ZM weapons: Complete guns, parts and kits for the high quality high priced ZM systems based on the AR15 designs but heavily modified.  The ZM weapons use a gas pistom system similar to that of the FAL and the AK47.  The folding stock is an Alan Zitta original and is probably one of the best designs ever made.  The downside is that these guns and parts kits cost as much as three times the price of a standard AR.  On the upside, a ZM derivative needs little or no improvement out of the box, as accessories like the Knight rail system, fore grips, metal folding stocks and low profile removable sites are costly options on standard AR15s.   Click here to go to the ZM website


Bushmaster: Considered by many to be the best parts and parts kits available outside of government contractors.  Bushmaster has held government contracts for the manufacture of M4 carbines from time to time and is known for high quality and good service.  Their prices are at the upper end of the scale for the more common parts dealers that deal directly with the public and their wholesale pricing is not much better.  Their quality is generally good, but quality control has lagged at times, especially when there has been panic buying based on impending legislation and their production facilities were running faster than normal.  They are also known to restrict the sale of parts in favor of the sale of complete guns or completed upper receivers (as opposed to selling individual component parts). 

Colt: Long the trade name synonymous with high quality AR15 rifles.  There was a time when Colt meant the real thing and everything else was just a copy.  Since the bankruptcy of the company and the sale of the trade name, the name Colt on a gun or gun part usually just means that it has passed their quality control process and the rest of the price means you are paying for the name.   Colt guns and parts have also been notoriously non-compatible with government specification guns and parts.   This has largely been an effort to curtail the illegal modification of Colt guns to select fire through the substitution of M16 parts.   Unfortunately, it also has meant that owners of these guns cannot easily obtain compatible replacement parts for those lost, worn out or damaged.  

Model One Sales: A descendant of the infamous Nesard of Chicago, this company sells only parts and parts kits of moderate quality at rock bottom prices.  Customer service is dismal and quality control is sporadic, but their low prices keep them at the top of the list of most home workshop gun makers.  A point in favor of their customer service is that they make all of their goods available with no questions asked as long as they are assured payment.  It is rumored that many of the parts sold by this company are made in Israel, the Philippines, China, Singapore and Pakistan.   Prices for Model one parts and parts kits can easily be 20% below those of other parts vendors.  For an average savings of $200 per gun, many gunsmiths will endure a little more work to get a functional gun, even if it means returning some of the parts for replacement if they are beyond help when it comes to fitting.  Model 1 dealer pricing structures are also fairly well set up to ensure reasonable profits fro those who buy in bulk, thus many small gunshow dealers use Model One sales as their source.  

DPMS: Another middle of the road parts vendor.   Middle of the road pricing and availability of different models, but above average customer service.   Much of their merchandise is made by Olympic arms, but they seem to carefully inspect the quality of the goods before sending it to you and they are more timely in delivery.  

Olympic Arms: One of the few parts vendors that is actually a full fledged manufacturer.   Customer service is average, but quality control and prices are nothing to brag about.  They have been improving their quality in recent years, but they still let some garbage out the factory door.  As a business, they have the advantage of being the only game in town when it comes to certain specialty items like pistol caliber upper receiver assemblies and stainless steel fluted barrels.  For many semi-custom items, if you are not dealing directly with Olympic, you are dealing with a middleman.   They are also usually the first people to come out with an item for general sale that would otherwise be a custom item.  They pioneered the market in "flattop" upper receivers. A private party seller with a very limited product line; basically bolt carriers at very very cheap prices.   Definitely a guy to contact if you are building a gun part by part and want to obtain parts from the lowest possible cost parts sources.   He commonly has the bolt carriers on Ebay.   Some have low grade finish and for still reasonable prices, full milspec chrome lining and parkerized finish.   

Magazines for the rifle come in many flavors, with the most popular being either US or Canadian government issue.   I personally favor the Canadian Thermold magazines, but the US GI mags are reliable and durable.   On the left are three grades of current issue US mags.  On the right are from top to bottom, A Ram-Line combo mag that also fits the Mini-14.  These are decent, but will usually not activate the bolt catch in either rifle.  In the middle is a US made but Canadian issue Thermold magazine, a personal favorite.  Bottom right is a Vietnam era 20 shot military magazine that is identical to the five shot magazines commonly found with older Colt AR15 rifles.


Hit Counter