Bedding a Rifle With MatchGrade Bedding Compound

By Nathan Foster

Instructions for MatchGrade Bedding Compound

Video and article tutorials

You can find matchgrade products and pricing here!

About MatchGrade Bedding Compound

MatchGrade bedding compound is a product that has been specifically designed and tested by Terminal Ballistics Research Ltd in conjunction with a leading New Zealand polymer resin manufacturer.

You will need:

MatchGrade bedding compound part A and B
MatchGrade release agent
Masking tape.
Insulation tape
Cling film (lunch wrap) or newspaper
Craft knife
Dremmel or chisels
Plasticine
A drinking straw (very important)
Degreaser (household citrus based cleaner will suffice if necessary)
Headless bolts (bolt stock) either ¼” UNF or M6 depending on rifle
Clean up rags
Sand paper, 120gr, 180gr, 240gr and 320gr.
Drill and drill bits- either M7 or 9/32 bits.

Mixing instructions for MatchGrade bedding compound

Pour part B into part A, mix well.

Clean up

Use vinegar (alkali) to clean equipment).

1.Stock Preparation

The first part of the bedding process is preparation. Remove the scope and strip the rifle down into basic components. Put all of the smaller metal parts (floor plate, bolts etc) into a plastic container. It is often best to remove the trigger unit from the rifle action to prevent compound from entering the unit. That said, you may prefer to have the trigger unit in the rifle for the purpose of visual alignment and clearance.

Once separated, the gunstock needs to be masked to protect it during the work process. It is best to use a layer of cling film or newspaper under the masking tape to minimize the amount of masking tape that actually contacts the stock. On wood stocks, the cling film helps to prevent the stock finish from being destroyed when the tape is lifted. On synthetic stocks, the cling film saves the mess associated with tape residues.

The next step is to rough up and key into the stock work so that the compound has both a good adhesion to the stock as well as a good build up of compound rather than a fine but weak shim. If bedding a plastic gun stock, the entire forend should be keyed and prepped for MatchGrade Synthetic Stock Stabilizer. This should be done as an intermediate step prior to bedding.

If the synthetic stock is not going to be re-enforced with MatchGrade stabilizer, the stock should be roughed up for a distance of at least 2” into the barrel channel. (Some forend flex will remain with this method on various stock models).

Use either a rotary burr (Dremmel/air tools/ die grinder) or chisel to remove stock material in the area of the action and tang. Some of the barrel channel will have to be roughed up but a decision needs to be made on just how far into the barrel channel will be the optimum distance for bedding. On plastic stocks, hot wire (blow torch/ gas cooker) can be used to key the stock for optimum adhesion of the compound.

To decide the optimum distance for barrel bedding:

For target weight barrels, put the bolt into the rifle action (even better if the scope is still attached) and determine the balance point. Hold the action in one hand and hold the barrel with the crooked index finger of the other hand. Slide the barrel along the index finger to determine its balance point. Once established mark this area of the barrel with masking tape and transfer this measurement to the stock.
For sporting barrels that feature a parallel area at the beginning of the barrel, bed to the end of the parallel.
On sporting barrels that lack a parallel, bed for a distance of (approximately) 1”. Accuracy can also be enhanced slightly by masking the sides of the barrel in a diagonal fashion.

Masking Taped gun stock

On wooden gun stocks, the user has two factors to consider. If the bedding job is to be absolutely discreet, great care will need to be taken during the removal of wood along the top edges of the action and barrel channel. Care must also be taken with brittle woods which chip easily during shaping. Unfortunately, the more the discreet the job is to be, the weaker the product will be at the top edges due to the poor concentration of compound in these areas. My own preference is for a tough, field practical job that will also resist moisture associated stock warping.

With Synthetic stocks, it is absolutely imperative to key into the sidewalls until an ‘overhang’ is created which will give the compound a mechanical lock. Further more, the top edges of the stock should show a good gap of 2-3mm (80 to 120 thou) for optimum strength of compound.

Diagonal masking on a Remington M700 Barrel. These barrels have no parallel at the breech (knox) but can produce great accuracy with careful bedding.

ir grinding the synthetic stock. On synthetic stocks, be sure to key into the side walls of the stock to create a 'mechanical' lock. The forend of this stock (Hogue) is also being prepped for MatchGrade Synthetic Stock Stabilizer.

Dotted line shows the reference point that will be used to establish the correct resting place (level) of the action. If the action sits too low, the magazine assembly will be sandwiched. If the action sits too high, the floor plate bolts won't reach through far enough to be screwed into the action. In some cases, the magazine will be sloppy and suffer poor alignment and feeding if the action sits too high. That said, bedding can be used to increase magazine capacity in certain model rifles as well as recanting the stock pitch to minimize recoil.

The prepped tang. In this example, I am prepping the tang of a Hogue stock that was factory fitted to an M1500 Howa rifle. This model stock lacks a good bedding contact area at the tang so I have placed a piece of foam (dotted line) out to a more practical distance and will fill this entire area. I will need to be careful that the finished result does not interfere with the trigger unit once it is re-fitted.

Check for clearance between the stock side wall and action metal. On wood stocks, a tighter fit is more discreet but lacks strength at the top edges and is not actually a great deal more aesthetically pleasing than a 'bedding border'.

The Hogue stock (without aluminum chassis) is the most difficult of all synthetic stocks to bed. In the picture above, a seam can be seen (running left/right). Below the seam, the stock is made of plastic but above the seam, the stock is entirely constructed of soft rubber. The rubber needs to be heavily keyed and for those who want the ultimate strength, small patches of carbon fiber or fiberglass mat should be inserted against the side wall when the bedding compound is applied.

2. Barreled action preparation

While the goal of bedding is to create a mirror image of the barreled action, it is imperative that certain areas of the rifle action are relieved (no contact with the bedding). This prevents the action from becoming pinched or ‘hung up’ in the bedding. If the action does become pinched, random harmonic vibrations will totally destroy accuracy.

The areas that need relieving are the front, sides and bottom of the recoil lug. Also the rear most face of the tang and any parallel wall metal on the action. These areas should be relieved with insulation tape or masking tape. Insulation tape is preferable as it does not bind with the compound and makes breaking the action out of the stock easier.

Sako rifles have an essentially square action. If the walls of this action are relieved with insulation tape or masking tape, the action will be a sloppy fit later on. Instead, on the Sako type action, the side walls should be given a heavy coating of release agent.

Above are the three basic types of rifle action. The red arrows show the parallel walls that must be treated with due consideration. The square shape on the left depicts the shape of the Sako action. The middle shape depicts both the Howa and Winchester M70 actions while on the right is the Remington M700 action. This last action is the easiest to obtain accuracy with as it does not have any parallel side wall metal.

Cutting tape for the front of the recoil lug. A film canister is the ultimate template.

The barrel also needs to be taped at the point where free floating of the barrel is to start (previously discussed in stock preparation). Once the relief areas have been taped, the magazine well should be taped to prevent leakage and Plasticine dams need to be used as required.

The headless bolts should now be masked to a thickness that allows them to only just pass through the holes in the stock. Japanese and European rifles normally utilize metric M6 bolts. On American rifles, the bolt diameter in ¼ inch however each maker has a habit of adopting unusual thread pitches. For metric countries, M6 bolts work fine in U.S rifles. The standard ¼ inch UNF thread pitch is not fully suitable for U.S produced rifles however, such bolts can be gently turned into the action at least a couple of turns, enough to plug the bolt holes and maintain alignment during bedding.

It is important that the user has some means to unscrew the bolts at the end of the job. Cutting slots in the top of the bolts so that a screw driver can be applied later is very useful. Button head hex bolts can also be ground down to suit. It is important to check that when the bolts are screwed into the action, the masking tape on the bolts is flush with the action leaving no room for the bedding compound to key into the bolt threads (see pictures). If using an incorrect thread pitch, check that the alignment of the bolts is square to the rifle action when these are gently screwed in place.

The Howa action taped and ready for the application of release agent. Before this final step, we need to double check the fit of the action in the stock.

3. Bringing the barreled action and stock together.

Once the action is taped up and ready to go, a final fitting is required to check stock fit. At this point, we need to make Plastercine dams in the stock to aid with the clean up and minimize any potential leakage.

Fitting the dams. Following this, the barreled action is checked for fit.

Fit the dams and shape the barrel dam to a nice concentric mold. Next, coat the Plasticine with a lubricating wax to prevent it from lifting out of the stock during these trial fittings. Lee case lube is the best lube for this use. Trial fit the rifle and check that the action and end of the barrel sink to the correct depth. Each time the barreled action is removed, the Plasticine in the barrel channel can be re-arranged for the best (aesthetic) fit.

The stock will need a dam at the tang, descending down into the trigger well. Finally, and this is very important, take a drinking straw, cut two pieces of around 2” in length to be used as dams to stop the compound running out of the king screw holes in the stock. Apply enough masking tape around each piece of straw so that the straws sit gently in the screw/pillar holes. The fit needs to be loose enough to ensure the straws can be easily pushed through the stock by the headless guide bolts when the action is put into the mortice (users can simply pull out the straws from underneath, as the action is pushed down into the mortice).

Once the action to stock fit has been checked, coat the action and barrel with release agent. Apply the agent with either a small soft bristle paint brush or piece of foam. Be sure to apply agent to the guide bolts as well. The release agent needs approximately 20 minutes to dry hard however in warmer weather, this time is reduced considerably and can be made to dry quickly using a heat gun.

Finally it is time to mix and apply the compound. Add part B to part A and mix well but not so vigorously as to create lots of air bubbles. The stock needs to be in some form of a rest at this stage. Use either vice or if working in the house, a small cardboard box with v shaped cuts at each end to serve as a rifle rest. Ensure that the compound is worked and forced into keyed areas and or drilled holes. It is critical at this stage that all plasticine dams are in place and able to perform their function, preventing compound from running out of the magazine, trigger well and stock forend channel. Following this, set the barreled action into the stock.

When setting the barreled action in place, do not use G-clamps or other ‘severe’ devices which may stress the action. The action should simply be either taped or bungied in place followed by a visual check on vertical alignment of the action (cant).

Once the barreled action is set in place, clean up the surplus compound that has overflowed from the stock. While doing this, leave a small bead of compound along the top edge of the action and barrel. Failure to leave some surplus compound on the top edge may allow suck back to occur during the curing stages.

Note# for those who prefer a stiff mix as opposed to the more commonly preffered runny consistency, the compound can be warmed by placing the mixing bowl on a hot water bottle. At high temperatures, the compound will begin to stiffen dramatically at around 20 minutes at 40-60 degrees. Obviously, the compound should be checked every few minutes to determine optimum consistency.

Bead of bedding compound at the breech and barrel parallel.

Bead of compound taped up and ready for curing.

4. Curing

A heat lamp over the rifle is ideal for curing however hot water bottles or even 1.5 litre coke bottles filled with hot water can be placed under or around and over the rifle. If using hot water bottles, wrap the rifle up in its blanket to retain heat.

During the first 10 to 20 minutes of curing with heat, the compound will soften and any air bubbles that have been inadvertently mixed into the compound. MatchGrade features a chemical air release agent within the compound which, combined with heat, helps dissipate air bubbling from the critical bedding surfaces. After 20 minutes and up to 4 hours; depending on heat and environmental conditions, the bedding compound will begin to harden. The rifle needs to be checked at hourly intervals for these first four hours to monitor hardening. Once the compound reaches a soft toffee like consistency, the bead of excess compound should be carefully trimmed away from the action to a neat finish. Failure to trim the excess compound away from the breach at this stage will make the job much harder to work with once the compound has fully cured. If a large bead of compound does fully harden, it may trap the action and prevent it from being lifted without damage to the bedding. Should this occur, the bead must be very carefully chiseled off while taking care not to mark the metalwork of the barreled action. In some cases, if the bead is not trimmed as described, small air bubbles may occur within the bead requiring a touch up fill later on.

With the trimming complete, the job must now be left to post cure for at least 48 hours. During this time, hot water bottles should be swapped once cooled. The ideal post cure temperature for this compound is 40 degrees C for at least 48 hours however fluctuations in heat as the hot water bottles cool are acceptable. If the job is pulled too early, the mixture will be hard but brittle. The same will occur in cooler weather if the job is left for 48 hours but without heat curing. Once the compound reaches full cure, it will be both hard and tough.

5. Finishing the job

Once the bedding achieves full cure, remove all tape that is binding the stock and barreled action together. Remove the action bolts. Apply two or three layers of masking tape to the underside of the barrel.

With the rifle upside down, hold the stock forend in one hand and strike the barrel (protected with masking tape) with a rubber mallet until the job begins to break out. Next, carefully wriggle the two pieces apart until fully separated. If a rubber mallet is not available, the parts can be separated by hand however the work is much harder and will require a good deal of brute strength.

Breaking the job out

Initial view of bedding

The stock can now be cleaned up and finished. Use a sanding block and sandpaper to true up the top of the barrel/action channel. Use a chisel or Dremmel to trim and shape internal run offs.

During the clean up, check for any masking tape debris or bedding compound burrs that could upset accuracy. It is always best to use a craft knife to scratch all corners, especially at the tang. Raised stampings (factory stamped letters and numbers in the metal work) that appear in the bedding should also be scraped flush. The breech face imprint should also be either scraped or chiseled as this area requires relieving.

Finishing work

Scraping away the breech face bedding. This area is just a thin line, about 3mm (120 thou) wide. In the picture above, I am scraping from the top of the stock channel, right around to the opposite top edge. The line can be seen due to its slightly lighter shade from my previous pass with the chisel.

When the job is complete, very lightly grease the metal work of the barreled action but not the trigger unit which should be treated with light grade oil. Assemble the rifle but when doing so, carefully observe the fit. If the fit is too tight, the rifle will produce fliers or stringing during shooting. In essence, the two parts should simply ‘fit like a glove’.

Another check that needs to be done is at the forend. Screw the action bolts (also known as action screws or machine screws) up tight and then loosen the front bolt a turn to see if the stock forend separates from the barrel. If any movement can be seen between the forend and barrel as this bolt is unscrewed, the action is under stress and needs further relieving. That said, the magazine box may also be pinched and out of alignment and should be the first check point in this instance.

Finally, the barrel channel of the stock must be checked to ensure that the barrel is free floating. Pressure point bedding at the forend should always be avoided unless a stress fault is occurring within the barrel.

Good shooting!