I have a beautiful Palma rifle with an English Walnut stock. Other than the usual maintenance of barrel changes and trigger springs I have never had to “re-pillar” the rifle. The only reason this term has even hit my lips is because of something that happened while shooting in South Africa last April. To travel with the rifles I had to take the stocks off of the action to fit in the travel cases. In most situations that is better anyway so the rifle does not get torqued or damaged while being thrown around by the luggage handlers. Regardless of the uber Pelican case, sh%t happens. Once in Africa, one of our captains tightened the action screws for me and off I went. Overall I shot well during the match but I was having unexplained elevation shots. Normally I can hold a very tight group. One thing I noticed was that the screws would be loose again after each day. Of course after the fact I should have checked them after each string. Another team mate Michael Storer had the same rifle stock as mine and was having the same problem. Our coach Emil loaned him his rifle and Michael went on to clean with all Xs the next two strings. What was going on here?
The theory was that when you travel to different climates the wood stocks will react accordingly. They may expand or contract depending on humidity and/or temperature. In our particular set ups the action screws were basically just going in to epoxy covered wood. I needed to have a metal bedding block put in. The main purpose of pillar bedding is to provide a solid foundation that allows the receiver to rest against without the possibility of materials breaking down and to minimize expansion and contraction in the various environments. Straight bedding material tends to degrade over time and will require a re-bedding but pillar blocks or even better bedding blocks should be fairly reliable for the life of the rifle. Usually these rifles can go a life time with no issues of stretching or stripping screws. But when traveled many times sometimes the screws won’t stay tight which of course will effect accuracy if everything is moving. We were proven correct when at the end of the S. Africa trip we tried to take the rifle apart to pack and one of the screws was stripped and we could not get it apart. We finally did get it apart but the screw and straight bedding it was in was toast. When back in the States my friend Ken Hagan of H&H Precision came to my rescue.
Ken understood perfectly what was happening even though I still did not. I asked him to explain to me what he was going to do. He was going to put in an aluminum bedding block. Not only did he explain but he even wrote it down and took detailed photos along the way of his work. How cool is that? Unfortunately the final result photos did not stay in his phone camera so we did not get that. But let’s just say that whatever he did worked. I went out and shot a perfect match at 600 yards with an 800/800 and with 54Xs!!! I have not held a group like that in awhile. Ken will be building my new bolt action tactical rifle with his action he has designed. Can’t wait! So here are his steps and photos and explanations of the bedding. To many of you this may be old hat. But I found it fascinating.
Stripped screw from previous bedding
Photo 1 – The problem: Expansion of the wood stock created stress between the screw and receiver bottom metal creating accuracy deficiencies. Eventually the stress on the threads will fatigue and strip out. This will often give the illusion the screw become loose so the shooter will instinctively try to tighten the screw only to find the screw continues to become loose again.
What is actually happening is the threads are fatigued and stretching or flattening out. Eventually the screw will may strip out and cause damage to the receiver threads as well.
Solutions: Add pillar bedding to minimize the expansion and contraction in various environments and to allow for a more ridged platform to bed the receiver against.
Not only does pillar bedding help avoid potential problems but it is a known fact the pillar bedding often times enhances the accuracy of a rifle.
#2 – As the screw is retightened in an attempt to secure the action, the bottom receiver threads seized and gulled causing severe thread damage.
Solution: Mill threads and re-tap new receiver threads.
#3The first thing we do with a wood stock that has been previously bedded is take some dimensions from reference points so that we can record the geometry of the existing rifle.
This is so we don’t change the existing rifle configuration or geometry such as action cant or line of sight changes. With most match shooters they become accustomed to a specific feel and ergonomics of their rifle. It only takes a few degrees in change and the rifle may become unsuitable for the shooter.
When we are done installing the pillars and finish the bedding we will go back and verify from our notes that the existing geomitry has not changed.
#4To keep the existing geometry we use a level so that during the milling process we stay parallel with the receiver.
In this case the rifle is placed in a milling jig and adjusted so that the bottom of the bed is straight and parallel.
This will insure the receiver screws will properly fit without any stress caused by misalignment. We want the screws to enter straight with no angles from the bottom metal to the receiver bottom.
Every wood stock is different so we cannot rely on anything other than the actual existing bed as a reference point.
#5We use an edge finder to locate the center of the hole to make certain we are in true alignment of the existing screw holes.
#6Once the center is found we then place a screw in the bottom metal and push up until the base of the screw is flush with the bottom metal.
This allows a quick check to make certain the hole is perfectly aligned with the spindle bore of the mill prior to milling the stock. We don’t want to drill a crocked hole that will cause a problem with alignment
#7Once the alignment has been verified we then set the mill up with an end mill for milling out materials to allow for the new pillars.
#8We then make a shallow cut to verify alignment and actual thickness of the existing bedding materials.
Later we will remove the existing bedding but only after the new pillars have been installed. Again we want the new pillars in place prior to rebidding the rifle so that we don’t make any unwanted changes.
#9We then go over to the lathe and make the pillar block from a solid piece of aluminum.
This can also be done prior to the other steps.
#10We then place the pillar blocks on the receiver to confirm the block are longer than required.
Using the previous recorded data we know how much to mill away after the pillars are bedded into the stock to insure the receiver fits back to its original position.
This will also be useful when we remove the existing bedding material the later so the bedding material can be removed without changing the geometry and position of the receiver’s original location.
#11We set the pillar in the shallow recess and insert a long screw to check for alignment before actually bedding the pillar block into position and continuing on to mill the holes to depth.
Pillar blocks are permanent so it’s important that everything is continuously double checked before installation. Once the pillar blocks are installed it if often difficult to make changes and keep their precision alignment and integrity.
Bottom line, under this particular scenario of working on an expensive custom stock that is used in world class competition it is imperative the pillars are installed correctly on the first attempt. There is no real good way to fix it afterwards if a mistake is made.
#12After Verification we mill out the hole to depth which is to the bottom metal surface. We continue milling about 1/10 of an inch into the bottom metal to insure we have a flat surface for the pillar blocks to mate against.
Then we insert the pillar into the new hole and once again check to make sure everything fits correctly and is still in alignment.
#13Once we are satisfied that both pillars are set to depth and alignment is good, we will then bed the pillars into the stock
#14After the pillar is bedded and the epoxy is completely cured we the place the stock back in the jig and mill the pillar down until it is flush with the original bedding material.
Now the pillar is at the same height and location as the original bedding material allowing the bedding material to be removed and insuring the receiver remains in the same position and location.
#15You will notice the black mark on the screw head. I use this black mark so I can count the exact rotations it takes before the screw bottoms out in the receiver. This is very important to insure the screw when torqued down does not hit the bottom of the receiver first before the action is tight into the stock thus not allowing the receiver to be fully secured into the stock.
We will then grind the screw down so that the threads are 1 full rotation away from bottoming out when installed in the stock allowing full thread grip. This will help insure the threads cannot be easily stripped. Keep in mind that the two screws will be different lengths so you must remember the longer of the two screws will go into the rear hole.
#16Now that we have the screws cut and ground to length we can now prepare to remove the existing bedding material and re-bed the stock.
A high speed wire brush was used to remove the existing bedding material. The wire brush creates heat that removes the bedding material but not the wood underneath.
Any bedding material that oozed into the inner hole of the pillar when it was installed is also removed with the same tool. We don’t want any material that might interfere with the screws and alignment when we go to bed the receiver.
#17We then use tape to create a relief on both sides of the recoil lug and on the front to allow for a few thousandths of an inch relief. This relief serves two purposes. 1. It allows enough relief so that the receiver can be removed from the stock later as well as installed. Without this relief the receive can become permanently locked into the stock which in some cases the stock must be damaged or destroyed to remove the receiver. 2. It allows for a little expansion and contraction of the wood itself without creating stress on the receiver when exposed to the different elements.
Also tape any holes we don’t want filled in with bedding epoxy.
We use a relief agent to help insure the receiver does not get locked or glued into the receiver as well which is applied before the receiver is set into the bedding material. Not using a good relief agent will most likely turn out disastrous later.
#18We can now mask off the stock and apply steel bedding material. Masking tape can be used to help prevent the bedding material from getting into the wood grain.
The bedding material tends to squeeze out and get onto the finished surface.
Once the material is done oozing out the tape can be removed and any final touchup and cleaning can be done using cotton swabs and vinegar.
#20A torque wrench should be used to insure even torque on both screws so that the receiver has no added stress. Most service rifles do not need more than 45 inch pounds of torque if the steel bedding is done properly. May people prefer the actions be torqued to 25 inch pounds to avoid any accuracy problems associated with over torque on the screws.
Here we torqued the screws just under 30 inch pounds.