Stocks: Bedding

Now that we've studied how stocks are made, it is time to study an operation called bedding. This is an operation that improves the accuracy and life of the weapon. So what is the need for proper bedding of the rifle?

1. Eliminate stress to the barrel and action, for longer life
2. Prevent flexing of the action when the weapon is fired for greater accuracy
3. After the weapon is fired, the action and barrel should return back to the same position on the bedding, to ensure repeatability of shots. This is called the rifle's ability to maintain zero.

Poor fitting of the stock to the action causes many problems with the rifle. This problem is further compounded because of expansion of the metal parts, as well as warping of the stock (especially in the case of wooden stocks). By removing wood from the areas of contact between the stock and the barrel and providing a much more stable substance such as fiberglass composite instead, the fit between the barrel and the stock can be much more precise and eliminate lots of problems.

There are many forms of bedding, but we will look at two major types: Glass bedding and pillar bedding.

Generally speaking, injection molded stocks are not really suitable for glass bedding. It is mostly used for composite hand laid fiberglass stocks, wooden stocks and laminated stocks. There are several ways that people bed the rifles. Some only bed the barrel and leave the action (firing mechanism) floating in the air, some only bed the action and the parts behind it and leave the rest of the barrel not touching any part of the stock, some bed the action and the barrel completely. For a rifle to fire best, there must be constant pressure dynamic between the stock and barrel throughout the length of the stock.

Glass bedding is done by using a slow drying epoxy. The epoxy should have the properties of hardening when dry and should not shrink or expand with temperature differences. To make sure that the epoxy does not dry inside the action and jam it, the trigger assembly is first disassembled. Then modelling clay and masking tape or electrical tape are applied along the holes to make sure that the epoxy doesn't enter there. Release agents are sprayed on or manually applied with a brush to key areas, such as the action and underside of barrel, to make sure that the epoxy does not stick there. In the case of wooden stocks, the surface of the wood in the barrel channel is lightly scraped away with a chisel to remove any oils and greases before the epoxy is applied. This allows the epoxy to get a better grip on the stock. The gun is assembled and epoxy is poured into the barrel channel and allowed to harden. After one or two hours, the excess epoxy is scraped away and then the rest is allowed to harden for a few days. After the epoxy is cured, the parts can be disassembled as the epoxy does not stick to the areas where the release agent was previously applied. The masking tape is also removed and the rifle is now ready for use. The two videos below show how the glass bedding process is done.

Pillar bedding was first invented by the Germans in the late 1800s for the Mauser rifles, but did not really catch on in the United States until the 1980s or so. With pillar bedding, two precision metal pillars are affixed to the barrel using screws, and holes are drilled in the stock to accommodate these pillars. The pillars were originally made of steel, but these days aluminium is more often used. It can be used with injection molded stocks as well as wooden stocks, laminated stocks and hand laid fiberglass stocks, since the vibrations are absorbed by the metal pillars first. The screws and threads on the pillars are precisely machined to allow micro-adjustments as needed. Holes are drilled in the existing stock to allow the pillars to pass through them. The rest of the procedure is similar to glass epoxying in that masking tape and release agent are applied and then epoxy is poured into the channel to harden around the rest.

Stocks: Adjustable Stocks

In the last few posts of this series, we've been talking about how stocks are made. Now we will talk about a class of stocks that are optimized for target shooters.

The above two stocks are made by a German company called J.G. Anschutz, which is well known for making stocks for world-class shooting competitions. The first stock is made of mostly walnut wood and the second one is a laminated wooden stock. Notice though that there are a few metal parts here. For one, the butt pad and comb are adjustable, so the user can adjust where their forearm is placed and where their cheek sits to peer through the sights. There is also a large U-shaped hole behind the grip for the user to place their thumb through. Actually, this particular shape of stock is so associated with the J.G. Anschutz company, that they're sold by other companies as "Anschutz-style" stocks.

The above stock is a McMillan A5. As above, the butt plate and comb are adjustable. The McMillan company is well known for its fiberglass stocks and its precision rifles. Canadian snipers used McMillan Bolt Action Tac-50 rifles to make some of the longest kills in sniper history in Afghanistan.

Stocks: Composite Stocks, Hand Laid Fiberglass Stocks etc.

In our last post, we studied one type of synthetic stocks. Now we will study some other types, made of many different types of materials, but all involving fiberglass somewhere. The first use of fiberglass in stocks was due to Chet Brown and Lee Six in the late 1960s. They later split up and Chet Brown later went on to found Brown Precision Stocks, which is still in business. Lee Six also continued to manufacture stocks and his company was later bought out by Kelbly Stocks.

At the low end, we have the poly-urethane foam stock. Predictably, these are made of polyurethane foam material. Of course, a stock made of pure urethane foam is not strong or rigid enough. Hence, many manufacturers add chopped fiberglass strands to the urethane foam. In addition, aluminium rods are added in some areas, particularly around pistol grips and the recoil lugs. Solid urethane foam stocks are generally lighter than other stocks, but adding aluminium and fiberglass adds extra weight back in, which undoes most of the weight savings. These stocks are not sensitive to moisture like a wooden stock. Unfortunately, they share the same problems of temperature as a wooden stock. They are also the stocks that are most likely to break.

Then we have the hand laid fiberglass stock, as pioneered by Brown and Six from the 1960s. In this type, a cloth made of fiberglass, kevlar or carbon fiber is first laid out on the inside of a mold cavity. Then a polyurethane foam is poured into the mold cavity and allowed to cure. Alternatively, a polyester or epoxy resin may be used instead. With an epoxy resin, the epoxy has a 3-D molecular structure and is lightweight. It is extremely resistant to impact damage and once it is 100% cured, it has extremely long life. Polyester resin is cheaper in cost. However, the molecules have a 2-D structure and it only cures partway (upto 70%) in the manufacturing process and continues to cure for 7 years or so, after which is starts to deteriorate. The outer cloth of fiberglass, kevlar or carbon fiber adds the necessary strength to the stock, that make these stocks much stronger than a foam stock alone. After such stocks are manufactured, a bedding process to seat the barrel properly on the stock is needed. This bedding process may be done as part of the manufacturing process, or separately after the stock has cured.

These stocks are much more expensive to make, as it is a labor intensive process. The curing time can take a while and much of the strength depends on the manufacturing process getting the amount of cloth and resin just right. On the other hand, such stocks are very light, accurate and immune to the effects of weather and temperature. Hence, these are the stocks of choice for many sniper rifle models and hunting rifles.

Stocks: Injection Molded Plastic Stocks

We will now begin our study of the so-called synthetic stocks. One type of stock we will study today is the Injection Molded Plastic Stock. These are manufactured using a typical injection molding process, which is used in plastic industries.

Granules of a thermoplastic material are loaded into a hopper and fed into an injection molding machine. A heater melts the plastic granules into a molten liquid state. The molten plastic is forced into a mold of the desired shape using a screw-type feed or a ramming plunger. The mold is cooled by passing a coolant fluid (usually water) through the mold via hose pipes connected to holes drilled in the mold. The molten plastic is cooled in the die and solidifies, upon which the die is removed and opened to extract the part. Any excess plastic is trimmed off using machining tools.

The initial setup costs are high because of the price of an injection molding machine and the price of machining a high quality accurate mold. However, once the setup is done, the costs of the thermoplastic materials and manufacturing cost of the stock are very low indeed, which drops the cost of each piece manufactured. In fact, the price of an injection molded stock can be far less than the price of a wood stock.

Two rifles with Injection Molded plastic stocks made by Weatherby

Injection molded plastics are usually "foamed", because the weight of a solid plastic stock would be excessive. The finished stocks are typically lighter than comparable wooden or laminated stocks. Typical time to manufacture an injection molded plastic stock, including molding and packaging takes about 30 minutes. The stocks can be manufactured to the same accurate dimensions every time, which makes them suitable for mass production.

Virtually every major firearms manufacturer in the United States makes injection molded stocks and there's a lot of advertising dollars spent on them. These stocks are usually marketed as weatherproof, shock-resistant, accurate, durable etc. So how much of this is truth and how much is hype, the reader asks.

It is certainly true that injection plastics are not affected by moisture, so fog and rain do not affect them. However, they are no more waterproof than a properly constructed laminated wood stock. It is also true that injection plastics are resistant to typical scratches and dings. However, it must be remembered that the material of the stock is a thermoplastic. What this means is that it does get affected by temperature. For instance, if a person were to leave his weapon locked in his car in the hot sun, it could cause the plastic to melt and warp the stock. Conversely, if the person left his weapon locked in the car during winter time, the cold could make the plastic extremely brittle and it could fracture due to a slight impact.

As for accuracy, it is true that injection plastic stocks can be manufactured to very accurate tolerances indeed. However, the flip side is that injection plastics are not as rigid as wooden or metal stocks. This means that it does not really matter if the stock is manufactured to very accurate dimensions, since it flexes when the weapon is fired, thereby affecting the accuracy of the weapon.

As far as durability claims go, it is certainly true that most thermoplastics degrade very slowly indeed, when exposed to the sun and rain. However, most of them are also susceptible to severe deterioration when in contact with liquids like ethanol, acetone, kerosene, ethyl ketone etc. As it happens, these are the very same solvents that are used in practically every barrel cleaner available in the market today.

Despite all the hype, the strength of an injection molded stock is actually not much different than a walnut wooden stock and is definitely easier to break than a laminated stock.

They are also ugly looking, compared to the beauty of a wooden or a laminated stock.

However, these stocks are among the cheapest types of stock to manufacture and hence, they bring down the overall cost of the weapons (or increase the manufacturer's profit margin!!) This is why practically every firearms manufacturer in the United States offers some firearms with injection molded plastic stocks. They are also lighter than stocks made of other materials.

Stocks: Metal Stocks

In our last post, we studied laminated wood stocks. In this post, we will study metal stocks. Metal stocks are a relatively modern development as far as gun stocks are concerned. The metals of choice are usually alloys of steel, magnesium or aluminium. Metal stocks are nearly always of the folding or sliding type, so that the user can reduce the overall length of the weapon as needed. One more advantage of metal stocks is that they lend themselves towards mass production.

The above weapon is an US-made M4A1. Notice the aluminum telescoping sliding stock at the rear, that allows the user to adjust the length of the weapon as needed.

The next weapon we see is an AK-47 with a folding aluminium stock. Notice that the stock attaches to the back of the rifle with a hinge that allows it to fold sideways. Also note that the stock is a skeletal frame. This is to reduce the overall weight of the weapon. Unlike the previous weapon, this one doesn't allow the shooter to adjust the length of the stock to the user's needs though.

It must be noted though that a metal stock does not always imply that the weapon is lighter. A skeletal steel stock is usually heavier than its wooden equivalent. Most metal stocks are also usually coated with a rubber or plastic material on the outside.

Metal stocks can be easily produced in large quantities via mass production techniques. Due to advances in machining technology, they can be produced to very accurate dimensional tolerances. They also have the advantage of being very cheap in price, compared to stocks made of other materials. Metal stocks generally provide superior rigidity than other types of stocks, but offer less in the way of dampening and absorbing shock. Some metal stocks have a shock absorber built in to handle the shock. Metal stocks will expand and contract with temperature variations, which affect accuracy. On the other hand, humidity does not have any effect on them.

Stocks: Laminated stocks

In our last post, we talked about classic wooden stocks, which have been used through much of the history of firearms. While wooden stocks are very beautiful to look at, they have the problem of warping, distorting and cracking in changing weather conditions. This makes the accuracy of the weapon suffer. Another problem with classic wooden stocks is that many stock blanks may have to be rejected because of some minor defects (such as a crack) in the wood. This makes complete wooden stocks more expensive because the manufacturer has to reject many pieces and find perfect stock blanks with no defects at all.

One of the solutions to minimizing this problem is to make a laminated stock instead. A laminated stock consists of separate layers of wood which are glued together. If the layers are properly arranged, then they cancel out each others' distortion and minimize the warping caused by humidity, temperature etc. The result is also free of internal defects. They are also less expensive to make, since cheaper wood can be used. The same blanks that would normally be rejected for classic wooden stocks because of defects, can be used to make laminated stocks, since the manufacturer can cut multiple layers of wood from the blank by working around the defective areas.

The Germans were the first to start making laminated stocks during World War II, for Mauser K98 and G43 rifles, when solid wooden stocks suitable for rifles became difficult to obtain. The Soviets were quick to adapt this idea around 1950.

The process of making laminated stocks is the process of making very high-quality plywood. To make a laminated stock, the maker first cuts thin layers of wood (1.5-1.6 mm. thickness or so). Each layer is individually impregnated under pressure with a strong dye. Since each layer is only 1.6 mm. thick, the dye permeates every bit of the wood, which provides a high degree of water resistance. Next, a waterproof epoxy resin glue is applied to each layer's surface and they are arranged so that the direction of the wood grain alternates between the layers. Alternate layers may also be dyed in different colors to produce an attractive appearance. The layers are then put under pressure and heated to set the glue. The curing process takes a few hours to complete and the glue makes the wood cells close to the surface of each layer almost completely waterproof. The alternating directions of wood grain between the various layers give the stock extra strength. The result is an attractive stock that is stronger than a solid wooden stock and almost immune to the effects of heat and humidity.

One of the major suppliers of laminated stocks to many small arms manufacturers today is the Rutland Plywood company, which sells their raw plywood material under the trademark "Stratabond". This company manufactures stock blanks for many well known companies such as Ruger, Remington, Savage Arms, Sako, Browning, Kimber, Boyd etc. The exact lamination process and the glues used are a trade secret, but it is known that they generally use birch wood layers for their stocks and use around 35 layers of wood veneer per stock. They offer blanks in several colors and patterns per manufacturer requirements and can make customized blanks as well. Some examples are shown below.

A laminated wood stock can be almost as strong as a fiberglass stock and look and feel the same as a solid wood stock. It also absorbs vibration better than a fiberglass or an aluminum stock. A laminated wood stock has more durability and strength than a comparable solid wood stock, has zero internal defects and can be made of cheaper material as well. It is virtually immune to the effects of temperature and humidity changes, thereby retaining its accuracy in a variety of weather conditions. It also has a pleasing appearance that can rival the best quality wood stocks. The only downside is that a laminated wood stock is heavier than the corresponding solid wood stock of the same size and material.

Stocks: Wooden Stocks

Of the different types of materials used to make gun stocks, the most common one used over the ages was wood. Since gun-making was always considered an art-form, it is no surprise to note that the work of making gun-stocks was usually entrusted to master woodworkers. These master woodworkers would generally use high-quality hard woods to make the stocks. The material most used was from walnut trees.

The requirements for a wooden stock generally are:

1. The material should be a hardwood which is reasonably dense, but not too heavy.
2. The material should be somewhat hard, but not brittle.
3. It should be relatively easy to machine.
4. It should preferably have naturally attractive patterns and grain (after all, guns were always well-crafted products made by skilled craftsmen and it wouldn't do to use low quality wood)

As it happens, walnut wood happens to fit these requirements the best.

The most high-quality walnut wood is obtained from the Juglans Regia, the Persian Walnut (or Common Walnut) tree. This tree is also known as the "English" walnut, because British sailors spread this tree around the world. This name is common in North America, because there is already a native American walnut tree of a different subspecies (Juglans Nigra) and so they call the Juglans Regia as an "English walnut" to distinguish between the two. The tree actually grows from Xinjiang province in China, all the way into Western Europe. It is commonly found in Northern India. This species has great genetic variability and the trees found in Western Europe tend to have larger size, but only one fruiting period, whereas trees in the Eastern range are smaller, but produce fruit for multiple years. English colonists and sailors also took this tree to the United States, Canada, Australia, New Zealand, South Africa etc., where it still grows. It was also introduced to Mexico, Chile and Argentina, perhaps by Spaniards.

The wood from this tree is often used in high-quality furniture and firearm stocks. The finely-figured walnut woods are called "English" walnut in the gun trade. Ironically, W.W. Greener mentions in his book, The Gun and its Development, (printed in the early 1900s) that a majority of so-called "English" walnut is not English at all. The walnut trees growing in England at that time were admirably suited for gun-stocks, but many lacked the rich brown color and figured patterns for customized high-end weapons and the second problem was that true English-grown walnut wood was not available in large quantities anyway. Therefore, many manufacturers actually got their wood from the European continent. He goes on to mention that English walnut wood is heavy, well marked, but not gaudy and says that French walnut is lighter than English walnut, has richer color with black streaks and open grain. He says Swiss and German walnut woods tend to be grey and pulpy, but if well chosen and naturally matured, they are equal to the finest French woods. He says that Belgian walnut is not available for sale in adequate quantities and Eastern European walnut wood is of very high quality and available in quantity, but is often not prepared or sawed correctly for the purposes of a gun-maker.

These days, France, Serbia, Romania, Greece, Bulgaria, Turkey, California and Chile are major producers of English walnut woods, while Australia and New Zealand are also beginning to up their exports of this wood as well.

Gun stock made of fine English walnut wood (J. Regia)

In the United States, the American walnut (J. Nigra, also called the "Black Walnut") that we mentioned earlier, is often used due to widespread local availability, particularly in the East coast. This wood has dark color and good density. Like the "English" walnut, it is also heavy and strong, but easily worked. It is extremely valuable and forest rangers are often called in to stop walnut tree poachers. In 2004, there was a poaching case involving one 16 meter long tree, which was worth $2500.

Gun stock made with American walnut (J. Nigra)

Another tree that was often used in North America for a few hundred years was the Curly Maple tree, again due to widespread availability, beautiful pattern and heavy density. Most of the famed Kentucky rifles used curly maple wood stocks. It has a characteristic flame or tiger striping pattern that makes it look very beautiful.

Replica Kentucky rifle using curly maple stock.

Curly maple wood is still used today, notably by musical instrument makers. For instance, rock and roll lovers may recognize many rock guitar players using the famous Gibson Les Paul guitar. Yes folks, that is curly maple wood on the top of that guitar as well.

Beech wood, Birch, Ash, Myrtle and occasionally Mahogany wood are also used for making some gun stocks. Beech wood is heavy, but does not have any pattern in the grain, like the woods seen above.

The grain of the wood contributes greatly to the strength of the wooden stock. It should ideally flow towards the toe of the stock for greater strength. The wood should also be prepared suitably -- it should be slowly and completely dried before working on it, otherwise it could split or lose color later. A high-end stock-maker will typically use wood that has been slowly air-dried for several years (7-8 years is common, but some are even as old as 20 years!), before attempting to machine it. Cheaper wood stocks are often kiln-dried and therefore more prone to splitting and losing color much more quickly. Air drying is what gives the wood the deep dark brown color. The best wood comes from the portion of the tree where the trunk and the roots join.

Here's a video demonstrating some of the things that stock makers look for, when selecting wood blanks to make a stock.

Wood stocks are the most beautiful to look at and have been used through much of firearms history, but they have a tendency to warp under adverse weather conditions. Due to this failing, modern military, hunting and sniper rifles usually use fiberglass stocks instead.

Stocks: Parts of a Stock

We will now study the parts of a gun stock.

The above image shows a typical English stock and an American one. The English stock was built with dimensions suited for about 80% of the sportsmen hunter population in England. Note that the English stock is built a bit more horizontal than the American one (2 inches displacement at the heel, vs. around 2.5" for the American stock). This is because American shooters generally tended to stand with their heads more erect and the same shooting style was also used in some other English colonies such as Australia and South Africa.

Public domain image from wikipedia.org

In the above image, 1 is the butt plate of the weapon (i.e.) the part that rests on the shoulder, 2 is the fore-end or fore-grip of the weapon. 3 is called the comb, which is the part that the user rests his/her cheek upon. The comb is built to support the user's cheek so that he/she can aim through the gun sights comfortably. Some combs also have a cheek-piece shaped on the side of the stock. 4 is the heel and 5 is the toe of the butt. This particular gun-stock, unlike the other two stocks above, has a grip (6) and a thumb-hole (7) for the user to put their hand through. Hence, this stock is called a thumbhole style stock.

The two types of stock are (a) one-piece stock (i.e.) the stock is composed entirely of one piece of wood and (b) the two-piece stock (i.e.) the butt is made of one piece of wood and the foregrip is made of another piece. The one-piece stock is generally used for bolt-action rifles, whereas the two-piece stock is used for assault-rifles, pump-action, lever action and break-open action weapons. Wooden one-piece stocks are usually more expensive to manufacture than wooden two-piece stocks, because it is harder to find a long piece of wood without blemishes, than it is to find two shorter pieces.

There are many factors important in shaping the stock.

1. Balance: This is the center of gravity of the firearm. If a thin thread is passed around the firearm stock, this would be the point where it would balance upon.

2. Cast-off or Cast-on: This is the amount that the stock is offset from the center when viewed laterally. A thin man may require a lot less cast-off than a fat man with stout shoulders, a right handed user may, due to a deformity, aim with his left eye etc. Usually, mass produced firearms don't have cast-offs, but custom-stocks may have cast-offs since these are produced for individual user needs. A cast-on is similar to a cast-off except it is done in the opposite direction for a left handed shooter.

3. Grip: The shape of the grip varies from stock to stock. Some may have the almost horizontal stock as shown in the English stock in the first picture of this article. Some may have a vertical grip like the thumbhole stock or a pistol grip, similar to that seen most modern assault rifles.

Stocks may be solid (i.e.) they do not change shape, or collapsible, such as a folding stock or a sliding stock. Sliding or folding stocks are generally features of military firearms.

In the above picture, we have an US made M4A1. Notice that the stock is two-piece, has a pistol grip and has an adjustable sliding stock at the back of the weapon, which allows the user to adjust the distance between the butt plate and the trigger to their own requirements.

Stocks

A stock is a part of the firearm to which the barrel and firing mechanism are attached. From the very first firearms, they have always been attached to some sort of stock, as the picture below shows:


In the illustration taken from an ancient manuscript, the reader can see that a firearm is attached to the end of a stick. A second stick is used as a support as well as a ramrod for the firearm. In most early weapons, the stick was made of wood. In fact, the word "stock" comes from the German word stoc which means "tree trunk."

In the very first firearms, there was generally a hollow socket in one end of the firearm, through which, the wooden stick was pushed into and secured. This is similar to the design of many spears of that era. The next development was the bombarde by the French and Italians. This was a small hand-cannon attached to a wooden stick. The stick was curved on the bottom side so that it could be placed on the shoulder and aimed with both hands, as shown in the first illustration below:

In the earliest firearms, people would manually light their firearms with a slow match. It was soon realized that a user could support their firearm better if they held it with two hands and lit the firearms with a separate trigger mechanism. This was the design adopted by early matchlock weapons such as the arquebus.

Soldier with an arquebus

Using both hands to aim the weapon, the user could then brace the weapon against his shoulder for strong support. In the above picture, note the shape of the stock of the arquebus and notice that the shape looks pretty similar to modern rifles as well. The arquebus stock design was so influential that the shape and design has stayed with us, almost unchanged, since the 1500s!