The Spartan Classic Gunsmith Adapter is designed to be embedded / inlet into a rifle stock and provide a secure low-profile attachment point for a Spartan bipod or tripod.

The information below offers some ideas and considerations for installing the adapter into rifle stocks that are produced in different ways (solid - hollow- carbon fibre.)

We produce these adapters in aluminium or brass, depending on the user's desired finish. The dimensions of machined cutouts are identical, and the same considerations apply to both designs.

The Classic Gunsmith Adapter is designed to work with the following Spartan products.

To safely perform this installation, the rifle action needs to be removed from the stock, which is why we recommend customers seek the help of a professional gunsmith if they are not comfortable with the process for their rifles.

The critical area for a successful installation is to ensure that all measurements are taken precisely. 'Measure twice -cut once."

Ensure that the adapter is:

Each rifle is different in this respect, and time spent assessing the correct placement is well spent.

The adapter is designed to fit into the stock in a specific orientation. (See the image below.)

Once the bipod is fitted into the adapter's socket, the machined cutouts in the socket can allow it to rotate only left and right (this provides the user with a muzzle traverse if desired). Alternatively, if the bipod is fitted in the reverse position, it will be locked in place, having no traverse (good for range work or longer-range shooting).

The two images below show the two machined cutouts of the Classic Gunsmith Adapter. (The 'Classic' range of adapters share this standard 12mm socket design.) The pin on the side of the Javelin bipod cant block (all designs) is located in either of these cutouts, depending upon the orientation in which the bipod is fitted.

In the photo below, the adapter is positioned slightly further back along the stock to account for the upturn of the 'Schnabel' fore-end.

Generally, though, the further the bipod is located towards the muzzle, the greater the stability can be obtained. Consider if the stock is strong enough in the far (muzzle) end. Some hunting stocks can be quite thin at this point.

Also, assess if there is a joint between different materials at the far end. This is a potentially weak position in the stock for installing the Gunsmith Adapter, as the joint often runs through the entire width of the stock at this point, and it is safer to move that installation point slightly further back.

For tripod use, it's sometimes desirable to have an adapter closer to the rifle's action, but this can depend on the available space.

We are sometimes asked if the adapter should sit in front or behind the sling stud. Ultimately, both options are suitable, but if you are a shooter who uses your rifle sling for additional stability whilst prone, you may wish to locate the adapter in front of the sling stud.

If there is a lot of tension on the sling, it could conflict with the bipod if the adapter is positioned behind the sling stud.

Consider if the position of existing sling swivel stud might impede the fitting of the bipod into the socket of the gunsmith Adapter.

It is worth considering if take it takes into account the need to manipulate the cant lever tension of the bipod, form the prone position. (If this is important to you.)

This applies if the adapter is in front or behind the stud. Remember that the bipod can be fitted into the adapter in the reverse position (180 degrees).

Is there is any internal or external chassis used in the stock? In the photos below the SAKO, S20 stock uses an external chassis that is covered by a polymer outer shell.

Because of its design, the rear-mounted adapter needed careful positioning to fit into the limited space between the machined lugs that are part of the chassis.

Customers who require opt for a second Gunsmith Adapter mounting option closer to the balance point of the rifle.

This second adapter can be beneficial when working in more confined positions, such as tree stands or hides, or where a longer wait is anticipated. Locating the second adapter closer to the rifle's natural balance point can allow the gun to be pre-mounted for use, but available for an instant freehand shot if required).

We've received positive feedback from users who endured long waits on driven wild boar drives in sub-zero temperatures and have taken advantage of this premounted capability to keep warm but ready.

We would recommend that you carefully mask up your stocks outer surface to prevent damage or marking.

The drilling process needs to be completely accuraly, so the best way to achieve this would be with a piller drill , and the stock clamped securely down. The stock needs to be mounted upside down in a suitable vice/clamp set-up so that it is level and perpendicular to the boring axis.

Use a good quality two-part epoxy containing sintered metal, with good mechanical, temperature, and moisture resistance.

The viscosity of of epoxies can vary. Some can be quite runny which can be advantageous if trying to get it to flow into small confined areas. The down side is that it will tend to find its way out of any areas that are not contained.

Alternative a 'putty' type expoxy is a little more forgiving if you are required to work or shape it slightly as it cures, as it tends to stay where you put it.

With some stock designs, it might be desirable to use an epoxy with less viscosity. This epoxy will find its way into small gaps and voids to achieve a strong and cohesive fitting.

There will be geographical variations of what is available, and other good-quality epoxy resin options will also be available. Please look for an option with the properties that you need. These are likely the same products used when bedding in rifle actions.

The generals guidelines to using epoxy adhesive adapter to bond the Gunsmith Adapter in would include the following:

You may be required to make a small former or ‘bulkhead’ to contain the epoxy within the area of the stock you would like to fit it into.

Using stiff cardboard or plastic cut to shape works well for this. Plumber's putty can also be moulded to form corners and shapes to contain the epoxy resin.

A simple soft wax applied to areas that are difficult to mask up or will be removed later can protect surfaces that you don’t want the epoxy to stick to. (Neutral-coloured wax shoe polish works well for this.)

The adapter is 17mm (0.6”) deep in total, but not all of this needs to be installed into the stock. If you look at the photos below, you will see that the rim of the adapter sits slightly proud of the stock, requiring only 10mm to be embedded into the stock itself.

The adapter is machined with channels designed to work with the epoxy resin bond agent to increase the strength of the bond. These channels are machined slightly smaller than the circumference of the top face of the adapter.

The minimum depth that the adapter should be installed upto approximately 10mm (the lower portion of the adapter with the machined cutouts.)

Subject to the amount of headspace available between the adapter's base and the bottom of the barrel, the adapter can be inlet deeper into the stock and, in some cases, flush mounted. Care needs to be taken to avoid conflict with the barrel from the adapter or epoxy bonding material and the barrel.

A Danish customer of ours showed what is possible with time and the right tools by sculpting his adapter to match the radius of his Sauer rifle.

In normal circumstances, this deeper type of installation can be achieved in most stocks where there is sufficient room.

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A 19 mm ‘Forstner’ bit should be used to drill a hole in rifle stocks made of solid material (typically wood or fibreglass). This bit is the most suitable for achieving a cleanly bored, flat-bottomed, blind hole, which is essential for a solid stock.

Ideally, the drilling process should be undertaken using a pillar/pedestal type machine so that the correct X & Y axis of the bore is maintained throughout the process and the hole is bored to the proper depth.

This will produce a hole that provides a clearance fit and sufficient room for the epoxy resin to form a good bond between the surfaces or the stock and adapter.

The image below shows a fibreglass McMillan stock, which offers the same strength as the solid wood stock for the adapter installation.

The good news is that these are the most straightforward stocks to fit the adapter into and tend to be the quickest installation to complete.

The link below this process being completed on the solid wood stock of a ‘Blaser’ rifle.

https://www.youtube.com/watch?time_continue=4&v=gfXRbB7W_ik

For rifle-stock hollow stocks manufactured from polymer material (typically but not exclusively), an 18mm hole saw works well. The hole produced will be slightly too small then the top rim of the Gunsmith Adapter. If required this can be enlarged fractionally with a small rotary.

A tighter fit between the adapters outer circumfrance and the stock may be beneficial, as the adapter is initially unsupported when fitted into the stock (unlike a solid stock)

as it can help to prevent the adapter from unintentionally moving out of alignment during the epoxy bonding & curing process. Another advantage is that the tighter fit helps to reduce the migration of the epoxy resin outside the stock, especially if a more viscous epoxy resin is used.

Hollow stocks require a little more preparation work than solid stocks, as the adapter will need to rely upon the additional support of the epoxy resin as a bedding material to hold it in position and manage the energy of the rifle in use.

Often, these types of stock are manufactured with several hollows or wells divided by a series of cross braces (similar to the bulkheads of a ship). These hollows are excellent for fitting the adapter, and the cross braces form perfect bulkheads to contain the epoxy and surround the adapter. Overall, this process has similar considerations to pillar bedding in a rifle action.

Once the hole has been bored to the correct size (graduel enlarging the hole with the rotary tool to create a tight fit for the Gunsmith adapter.

The adapter and internal surfaces should be keyed, cleaned, and degreased to give the epoxy adhesive a good surface to grab onto.

The adapter should be positioned to be orientated correctly and to the correct depth. Masking tape can be used to ensure that it doesn't move during the bonding & curing process.

A consideration for stocks that have a moulded structure running centrally along the length of the stock (similar to the image below) is to fill the fitting area with epoxy resin before boring the hole. This effectively turns that portion of stock into solid stock and can reduce the chances of the cutter 'wandering' as it moves over the thin polymer spine.

Another advantage of this that the Gunsmith Adapter is supported and the bonding process is identical to the solid stock method.

Some stocks have very little inside them, and in these cases, it is a good idea to build up a larger body of bedding material inside the stock to support the adapter.

The image below shows a Weirauch PCP rifle stock. The wood is relatively thin along the base & hollowed out inside.

In this case, the adapter was positioned towards the front of the well in the stock to obtain as much support from the front face of the well.

A body of Devcon putty built up around it. This is an excellent example of how thicker epoxy can be helpful.

In these cases, the epoxy not only supports the adapter but also reinforces the thin material of the stock, which is relevant when the adapter is subject to loading when used with the bipod or tripod.

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Carbon fibre stocks can accept the fitting of the Classic Gunsmith Adapter, but their structural design needs to be carefully assessed before starting the installation.

These stocks may be hollow or solid in design. All carbon fibre stocks require extra care when drilling to avoid chipping the resin or catching carbon threads. It is essential to ensure that the tools have sharp cutters.

Other designs of carbon fibre stock have been formed using airbags or inflatable formers, which are removed once the epoxy resin is cured. The stock is hollow, so consider providing additional support around the adapter.

Where a carbon fibre stock is formed by laying up multiple layers of carbon fibre material to produce a lightweight, rigid structure, it is likely to be hollow. There are many variables with this type of design, but in most cases, epoxy resin material will be necessary to firmly support the adapter in the stock's hollow void.

Because the stock has limited access, drilling an additional access hole(s) from the top side may be necessary to allow the bedding to be fully applied and any former material or dams to be shaped and positioned.

In the images below, the top face of the stock has been used for this purpose.

In other cases, the stock is formed by laying the carbon fibre material over a foam core to produce the rifle stock. These foam core composites are intended to produce highly lightweight composite structures while maintaining their lightweight and low water absorption.

In the image below, you can see the foam core from a SAKO Carbonlite rifle. SAKO uses a carbon fibre sleeve (like a sock with the toes cut off) that slides over the foam core before the assembly is mounted into a press, where the epoxy is injected into the carbon fibre weave. Once cured, the carbon fibre material and epoxy create the strong but light material we recognise.

Because the 'skin' of carbon fibre material is thin, the 'point' loading created by mounting a bipod needs to be considered. This issue becomes more relevant when a bipod is fitted due to the more significant loading and kinetic energy produced when the rifle is used with a bipod.

In the image below, you can see the finished carbon fibre stock from a SAKO Carbonlite rifle now covering the foam core.

Because the stock's foam core is a relatively soft closed-cell foam material, simply boring a hole and bonding the adapter in place in the same way as a solid stock can cause the adapter to move as the foam core is compressed due to the bipod being loaded or recoil.

In the image below, illustrates the need to undertake preparatory work rather than simply drilling and bonding directly into the stock and failed in use due to a lack of support, which allowed it to move, debond, and break out of the stock (SAKO Carbonlite with custom paint finish).

As with all such installations, it is essential to mask the stock to prevent unwanted marking and accurately mark the position where the adapter will be inlet into the stock.

It is essential to position the hole along the central line of the stock.

Mount the stock under the drill (a pillar drill is ideal for this purpose) and ensure that it is horizontal to the direction of the drill and firmly supported and clamped. (Leave this mounting arrangement set up for a second drilling process later on.)

The image below shows how much the carbon fibre layer is around the foam core.

Using a 19mm Forstner bit, bore a hole to the full depth of the inner stock to remove most of the inner foam core. In the image below, you can see the flat base and sides created. (Note the air space created by an air bubble when forming the foam core.)

Please make sure that there is enough room around the adapter's total circumference and under its base.

Removing some additional foam core material from the stock is necessary to form the extra space for the epoxy bedding material.

To achieve this, we have found that a set of small wood carving gouges is ideal for precise and clean removal of the foam core.

By carefully slicing away small amounts of the foam core, you can build up a uniform space around the circumference of the adapter and the base, leaving room for 3-4mm of epoxy resin bedding material to support the adapter.

Ensure that the area under the face of the stock is also cut away, and the area under the base of the adapter.

At this stage, it might be tempting to apply epoxy to the hole and install the adapter, but we advise against this approach. While it could be successful, there is a risk that the bond between the adapter and the epoxy and the inner stock and epoxy could be compromised.

This approach tends to create air pockets in the epoxy bedding material, forcing the epoxy out and lifting the adapter out of the hole.

To avoid this, we recommend adding additional steps.

Fully clean the hole so that it is free of foam shavings or dust.

Fill the hole completely with the epoxy resin material. Use a small stirrer-type stick to tamp the epoxy into all areas. Let the epoxy cure.

Refit and clamp the stock to the drill bed in exactly the same position as the original drilling position and redrill the hole.

As discussed earlier in this article, the minimum depth to install the adapter is 10mm, but if desired, it can be installed a little lower.

Clean the redrilled hole and key the surface of the adapter to aid adhesion to the epoxy. Clean away any dust or grease. Apply a thin coating of epoxy resin to the parts of the adapter that are to be installed into the stock and to the sides and base of the hole.

Install the adapter fully into the hole. If you feel any air pressure, gently twist and rock the adapter until the air is expelled.

Ensure that the machined slots in the adapter are perpendicular to the line of the stock. Consider applying a stripe of adhesive tape over the adapter to secure it in place.