Re: Action screw torque...
I'm certainly no areospace engineer but the main definition of "torque" will lead you to a "turning or twisting force" as it correctly applies to anything in the world of machinery that turns under power, or applies power to a shaft. Torque by definition is something rotating, receiving power and/or applying power, ultimately generating a "load" upon a system to do "work". A common household use of the word "torque" is in the marketing strategy used to sell you a more powerful pickup truck.
Unfortunate in the world of fasteners is the use of the word "torque" to describe how "tight" a fastener is twisted, as it risks the misconception, or misrepresentation, of what is being measured. Most would assume that the fastener, or base components, are actually being taken out of shape to some measured degree in relation to the value of "torque" being applied. That certainly can and does happen in the extreme as seen by anyone who twists off a fastener; or "pulls out the threads" by over tightening it; or has a fastener break later due to over stretching it. However that scenario is why we have recommended "torque" values for any given fastener; to greatly diminish, or prevent such occurance as going beyond the designed limits of the fastener itself. If a fastener is tightened between the recommended specifications of a high/low, or no more than a recommended high, then the fastener is in no danger of breaking and the clamping action produced is as required.
A "torque" value on a fastener, as it concerns most things normal and ordinary, is simply a measure of the friction upon the threads. This is why we can experience a discrepancy between a lubricated fastener and a non lubricated one; a dirty fastener, and a clean one. And this is also why we are usually allowed a higher "torque" value being placed on a "fine" thread fastener as opposed to a "course" thread one. A fine thread fastener, such as the 1/4-28 on our M700's, allows for more friction to provide a more stable clamping action than a 1/4-20 would. In essance, the 1/4-28 makes it a stronger connection because we can apply more friction to the device (screw) that provides the clamping action; thus the higher friction attained makes it less likely to loosen by overcoming any forces applied to it that could vibrate or otherwise compromise the connection's integrity.
As this applies to tightening a rifle's action screws it behooves us to completely understand this force of friction as it retains the clamping action, and how/why it's achieved. To that end we must understand such things as what is too little and what is too much, and allow ourselves to fall somewhere in that range. We must realize that a rifle's action does flex out of shape and the amount of tightening on the action screws, in combination with a recoil lug, is designed to overcome this force, to maintain what we all ultimately deem to be "repeatable accuracy". <span style="text-decoration: underline">In a nutshell, properly torquing a rifle's action to a specific amount of tightness is, first, how we achieve a repeatable platform from which to launch a bullet; and second how we avoid the need for any other thread locking system, such as loctite, or lock washers, etc. It relies completely upon the friction of the threads to hold fast the connection, and allows us to remove the connection, easily, when necessary.</span>
Nothing more, nothing less.......
We often argue about the difference between "torque" values without realizing the actual difference between the values we argue. We measure our action screws in inch pounds, which are 1/12 of foot pounds. A close cousin to our M700 action screws is the common socket head cap screw. The common recommended "torque" value for a dry non-lubricated 1/4-28 socket head cap screw is 16 foot pounds, or a whopping 192 inch pounds, far, FAR beyond the values we argue concerning a rifle's action screws. Debating then, between 40 inch pounds, or 50, or even 60, seems rather trivial, at best, regarding what the screw itself can "take" in a clamping load.
Does this mean we all can safely tighten our action screws to 192 inch pounds? Of course not, because other factors come into play that lessen the allowable degree of "torque", such as the integrity of the base components being clamped; things already long ago determined by rifle manufacturer's, and stock makers.
Personally I understand the difference between an increment of 5 or 10 inch pounds, and am fully aware the difference between 40 inch pounds and 60 inch pounds is inconsequential to the platforms I shoot, as it's well within the spectrum of what the system can mechanically "take". I find that 50 in lbs on my short actions, and 55 in lbs on my long actions is where my stress free bedded and pillared actions tend to like to be, per repeatable accuracy.
I don't own occasional shooters or safe queens, I own tools. Never have I found a rifle that for some reason or another didn't require a routine breakdown for preventative maintenance and general cleaning. I've never found that dirt, dust, grit, or other field debris is conducive to the overall good function of an accurate rifle. Just keeping crap out of a rifle's free float, or fire control, requires taking the action out of the stock. Therefore I require an exact repeatable tightening of the actions screws to return the rifle to it's known zero.
The only suggestion to a question of "torque value" that makes any amount of real sense is to abide by the manufacturer's recommended value, and not exceed that, regardless what the www tells us on forums. As long as we do not go beyond the manufacturer's limit we are operating within a range, and hopefully finding a value that best suits our rifle's function. In that context, within those limits, this really is a to-each-his-own situation with no genuinely debateable right or wrong answer.
