http://www.milsurps.com/showthread.php?t=42818Tightening method for rifles with single-piece stocks
Before doing anything, please remember that we are concerned with achieving a stable fixing of a complex piece of metal in a piece of (typically) rather old wood. We are not changing a wheel on a truck, so the “tighten it until it squeaks” attitude is out of place here.
The following procedure applies to all Mauser (and similar) actions with a threaded lug on the bottom of the barrel ring section of the receiver, and a corresponding boss/sleeve on the front of the trigger guard. If you can adjust the bedding so that when these meet, the wood is neither crushed nor loose, but compressed, i.e. still elastic, then the setup will not be critical with regard to screw torque. You simply tighten up the screws to what I term "2 fingers and thumbs tight" if you are using both hands on a wrench with a tommy bar (as you should), preferably fixed in a drill press (even better).
"2 fists tight" is not only pointless, it may damage the thread, bend the trigger guard, and crush the stock wood. And if you do damage the thread you will discover that the thread pitch is something unusual (=expensive) when you look for a tap and die to clean it up!
At several points there will be alternative solutions, and only you can make the “hands on” decision as to which is more appropriate.
Prodecure
To prevent the shock loading which is caused by firing from shifting the barreled system back in the stock, the recoil lug must be bearing properly on the recoil cross-bolt (in Mauser-style systems) or the equivalent portion of the stock.
If the system can be driven back by the shock of firing, then that tends to cause a splitting of the neck - if there is not sufficient clearance behind the tang. The tang is forced into the recess in the stock, where it spreads and finally splits the wood at this point.
So first of all, assemble the rifle with the front trigger guard screw lightly tightened. Just enough to prevent slack. The rear trigger guard screw should also only be tight enough to stop the tang moving vertically.
Now hold the rifle upright, and bang the butt down very sharply on a piece of soft wood. This is to drive the system (and the tang) back as far as it will go. Inspect the wood around the tang. There must (not should - must) be a clear gap all around the tang. If the tang is jammed up into the end of the recess, then the rifle is a candidate for a neck split when firing real ammunition. The gap does not have to be huge - about 1/64 is adequate.
If there is no gap, remove the barreled system and carefully enlarge the edges of the recess until an adequate gap has been achieved. Alternatively, the recoil lug /bolt contact face can be shimmed to create the necessary tang clearance.
Now reassemble the rifle, applying a light torque on the front screw. Does the tang rise up out of the recess as you increase the torque? If so, the tang will indeed be bent when both screws are properly tightened. And so will the stock! The system is not properly bedded in the stock. It may be necessary to shave off tiny amounts of wood from the stock to achieve even bedding. Or, of course, use a bedding compound – but that’s another story.
However it may be that this is simply a result of wood movement over decades, and the bedding surface is flat enough. Loosen the trigger guard screws and see if the system can be rocked in the stock by pressing alternately at front and back.
If the system appears to sit quite flat, and the tang is well seated in the recess, then there is an alternative. When the front trigger guard screw is fully tightened it should compress the wood, to hold the system firmly but not crush it, which is a permanent distortion of the wood. The wood must remain elastic, and that is why the seating of the system in the stock should only be adjusted when any cleaning/re-oiling with linseed oilicon has already taken place, and (preferably) the stock has had a week or two to settle down.
The inevitable shrinkage of even well matured wood over the best part of a century may mean that if you tighten the screws up to a plausible torque you are, in fact, not just squeezing the wood but also bending the stock. This is a recipe for making a rifle that reacts badly to changes of temperature and humidity, and must be avoided.
On some of my rifles I have therefore judiciously used shim washers between the sleeve on the trigger guard and the threaded boss on the system, so that when the metal surfaces meet, the wood is compressed, but not crushed. Think of the wood as being a very fat spring washer - it should be neither crushed flat nor sloppy.
If you get it right, the tang will not rise more than a gnat’s whisker when you tighten the front trigger guard screw to full torque. The gnat's whisker is desirable so that when you tighten the rear trigger guard screw it is also compressing the wood, but not crushing it. Here too, careful use of shim washers may also be indicated.
Well, that’s the way I do it. It may not be theoretically perfect, but the results show that it’s not a bad method. The use of an expression such as “gnat’s whisker” is just facing up to the fact that, in the end, a certain amount of feeling is required.
And, finally, after shooting a refurbished rifle a while (say, 20 shots) check it all again! I forgot that the first time with my M1917 and had the unnerving experience of finishing a competition by holding over to keep the shots in the black, because the system had loosened up!
Give it a try!
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That applies to wood stocks. I have observed that my wood stocks will swell on high humidity days and seasons. That surely changes the pressure or compression on the screws. Synthetic stocks presumably won't react in the same manner.
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Torque inch pound figures.
http://www.thehighroad.org/archive/index.php/t-555527.htmlLooks like 50 - 65 inch pound range is mentioned a lot.
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http://www.amazon.com/The-Mauser-through-bolt-actions/dp/B0006EY9M0
