@ 10:25 am (GMT)
Nathan FosterHi Ryan, the short answer, is to utilize both full length and pillar bedding.
Regarding pillar bedding, pillars are best utilized where there is a risk of stock compression over time. This is most apparent on on wood stocked rifles because the wood fibres can become crushed, resulting in a split stock. This occurs especially on older rifles where oils have continually run into the wood fibres but in contrast can also occur with dry, brittle stocks.
In my own processes, I pillar bed wood stocked rifles but do not usually pillar bed plastic or laminate stock rifles. However, each rifle must be taken on a case by case basis. Occasionally, I will come across a plastic stock design that shows a great amount of flex between the king screws, requiring pillar bedding to prevent stress. As for glass stocks, the HS and B&C ali chassis rifles have the ali to prevent compression, the McMillans do not have this and pillars can help prevent cracking.
A couple of things to bare in mind. I don't induce stress to the stock during bedding. By using a bunjy system during the bedding process, stress is eliminated. Using the king screws and floorplate can induce great stress and if you look at page 78 of the PP presentation given by Hi Score Gunsmithing, you will see that they use this process and warn that if it is not done carefully, the action will be stressed. I would rather not go down this path, instead using headless screws and bunjies. Also, the sides and front of the recoil lug should be relieved, not just the bottom and along with this, it pays to mask off the stock, not leave it bare. A bare stock is prone to knocks and bumps during work and any missed compound spills in areas such as the checkering will be frustrating to remove once the job is completed.
Recently, I have been working on quite a few T3 and Remington SPS rifles with plastic stocks. I stabilize the skeletons first with our stabilizer compound, not just the forend but also the skeletal areas of the action. This makes for an immensely rigid, solid stock and by the time the steel based epoxy bedding goes over this, stock compression is no longer an issue. However, this still does not mean that the king screws should be tightened severly. The T3 is quite sensitive to king screw tension, effecting vibrations within the action.
Pillar bedding can be done in one of two ways. The wide type pillars used by Hi Score are one method and you can see they have gone to a great deal of effort to create a good system. The other method is to use a narrower pillar, cut it to size, taking measurements from your stock, epoxy the pillars in place, then bed over this, again using headless screws. The difference between the two systems is that the second method results in a counter sunk pillar- there will be a light layer of compound over the pillar and it can only be seen from the bottom of the stock. Again, stock compression is eliminated with this system. The advantage of the narrow pillars is especially noticeable on narrow tang rifles where, if a wide hole is drilled, the entire tang area may be compromised. At the simplest end of the scale, aluminum arrow shaft, cut and final-sized used a lee case cutting tool is directionally- immensely strong when epoxied in place. This is ideal for rifles such as the Weatherby Vanguard / Howa.
Remember that a good layer of bedding helps a great deal. Skim bedding jobs always turn out to be a real disappointment down the track, especially with the non metal filled epoxies that lack density.
With your M70, if it utilizes 3 king screws, you can use either the Hi-Score method of utilising the floor plate during bedding or my suggested bunjy system, the former system requiring greater care. Also, you can still use the Hi-Score kit with bunjies if preferred. Our instructions can be utilized with regard to areas to be relieved and the application of dams. A major difference between the compounds is that the Hi Score is not a runny type compound. Our compound used to be a stiff mix but based on end user requests, it was changed to a runny mix in order to be more effective at filling voids. Regardless, between both sets of instructions, you will have a good volume of information to work with.
When re-assembling your M70, regardless of how you bed the rifle or which system you use, you will have to be careful not to over tension the middle king screw. You can use either loctite or even a small amount of thread tape to nip the screw into place, without stressing the action. This is the one weakness of the M70 if not properly addressed. Following this, after re-assembly is complete, check the bolt locking lugs to make sure contact is even. If the contact is uneven, the lugs will need lapping.
Below are some of the most recent rifles I have been working on showing full length bedding and also the stabilizer compound in conjunction with full length bedding on the SPS and T3 stocks.