Torque as some of you will know is rotational force. You apply torque with your arm when using a screwdriver for example. If you apply too much torque you may snap the head from the screw, too little and the screw will not hold materials firmly together. The application of measured torque is important because the correct mating of surfaces in a firearm can have noticeable effects on accuracy.
Torque and Zen
There are three primary areas which require consistent measured torque. The action and chassis/stock are more often than not separate articles (with a few exceptions). If there is any play between action and stock then this can lead to degradation in accuracy. Some of you may recall the difference between the old style Remington 700 wooden stock and a modern Aluminium chassis/stock system (from around 3.5moa to 1moa). That difference was due to the slop in the wooden stock which had been roughly inlet for the action.
The original stock on a Remington 700BDL model. You can see the imperfections in the wood which lead to inconsistency in mating surfaces.
The modern Aluminium version can be machined to very tight tolerances giving a snug fit. That snug fit is totally dependent on the screws connecting both parts.
A modern stock/chassis based around the classic Remington 700 action. Dolphin Gun supplied a large lug which provides a perfect flush fit to the machined recess in the chassis. Surfaces mate superbly and the v block chassis system negates bedding.
Many bolt action rifles have a classic two action screw set up – one screw in front of the trigger guard and one behind or in the grip. There are rifles which have different placement or number of action screws so check your diagram before loosening or tightening things at random. There are a variety of opinions regarding the exact torque settings. Now if you really want to get Zen about things you could take a range of suggested settings and load test your rifle with several different settings. Different levels of torque on the action are going to effect barrel harmonics so I feel it is a relatively simple and worthwhile procedure. I undertook this testing on a Remington 700 Varmint barrelled action and Manners T5 stock and mini chassis. The rifle certainly had a preference.
Recommendations for action screw torque settings.
Remington 700 type action in standard stock (no mini chassis) is 1.1NM – 1.7NM (Remingtons data). This is in my opinion because non bedded standard stocks are poor quality and lack the strength to torque down the screws further.
Remington 700 into a mini chassis/bottom metal is 5.1nm to 7.3NM.
Tikka rifles between 5.7NM- 5.9NM
Winchester standard stock 2.8NM
AI AICS/AX/AT 6NM
Many modern chassis’ to custom actions 5.1NM – 7.3NM
Many companies give a band rating i.e from x-yNM and leave the exact number up to you. It is certainly worth asking the manufacturer of action and stock/chassis what they suggest you use as a starting point.
I have a manners stock and mini chassis. Manners suggested 7.3NM at the front screw and 5.1NM at the rear. They went on to suggest the front screw should be tighted first which in theory allows a “properly floated tang” (their wording). I tried their spec and found it did yield better accuracy than my previous setting of 5.1NM for front and back.
The next area that benefits from correct and consistent torque are scope mounts including rails, mounts direct to action and the scope retaining screws on the rings themselves. Lets start with the rail to the action.
Rail/Base Direct To Action
Popular manufacturers are recommending between 1.7NM and 2.8NM. It would not be good to have slop between mating surfaces here as it would allow the scope to move slightly under recoil. A slight movement which goes unnoticed at 50yds will be magnified with increased range. You may find hits at 1000yds+ impossible as the cone of fire will shift unpredictably. Equally concerning is an overly tightened screw snapping leaving itself buried tight in the action thread – a drill out job and some gunsmiths time..
Badger Ordanance 1.7NM to 2NM
DNZ 3.3NM to steel receiver and 2NM for Aluminium.
Some will use some thread locking compound on picatinny/base screws. Personally I have never had need.
Cross Bolt Screws
Most scope bases have screws requiring set torque along the bottom edge. Some tactical models offer quick release levers which are designed to lock at hand tight.
An example of quick detatch rings which do not require specific torque setting..
Those with screws usually tighten against a clamp (crossbolt) which grips the picatinny rail. Again it is important there is no slop allowing the scope to move. Overly tightening these can crush sections of picatinny rail making any future mounting to that area impossible. I have seen quite a few rails damaged in this manner. The recommended specs for these are much broader so care must be taken to follow your manufacturers data.
Vortex 5.1NM – 5.6NM
Many mounts require the crossbolt screws to be tightened in a certain order or rate. Ignore such advice at your own peril. If manufacturers have taken the time to have their engineers produce a guide then there is a good reason for it..
The last screws to consider are those on the rings themselves. These screws clamp the scope tube in the rings. They generally have a lighter recommended torque value as they are usually the smallest screws in this area. Over tightening can result in two outcomes which are both very common. The thread can become stripped on the screw, the ring, or worse you can dent the scope tube. The tube contains delicate moving internal parts which could be adversely effected and make your scope useless..
The ring screws do have a tendency to work loose over time so a small dab of thread lock is sometimes used. I prefer not too as mentioned previously and I simply check for tightness regularly.
Spuhr 1.7NM – 2.8NM
DNZ 2.8NM – 3.4NM
Seekins 1.7NM – 2.2NM
Barrel Retention Screws
You can see the single barrel retention screw above the front palm rest on this AI AXMC.
The last screw I would consider for careful torque setting would be those used for barrel retention in the new era of switch barrel rifles. Most of these weapons are a result of the US Military PSR contact which invited gun manufacturers to submit sniper weapons against a tight set of requirements. One of the requirements was a multi caliber system which was user changeable in the field within a short time. The Remington MSR won the contract and remains somewhat of a unicorn to non military users mainly down to the price (currently around $20,000). The other competitors have proved popular in both the civilian and foreign military markets. Some of these rifles require specific torque for safe and effective barrel retention, something you definitely do not want failing on you mid shot..
Below are a few rifles which have barrel retention screws.
Accuracy International AXMC – 5.5NM
Desert Tactical Arms SRS – 7.9NM, HTI 9NM
FN Scar 16/17 – 7NM
Barrett Mrad 11.3NM
Steyr HS50 – handtight!
Some weapons manufacturers go as far as to provide a pre-calibrated torque tool for use on certain screws (Accuracy Internationals torque tool for the barrel retention screw being an example). These brand specific tools can be expensive and tough to source. They generally only have one torque setting so as not to fall foul of human error in field use. If you do not need to change barrels on a battlefield then I think a torque wrench with a range of desirable settings is the best option. You can use it for a multitude of weapons if you pick something with a sensible range.
I should mention here that all torque figures quoted thus far have been in NM (Newton Meters). Many manufacturers list inch/lbs. I am careful not to list using inch/lbs in case people mistake it for foot/lbs and end up breaking something. The inch/lbs value can easily be converted online into NM (just search “convert inch pounds to NM”).
I would seriously recommend a quality adjustable torque wrench with a 1-20NM adjustment. This should cover all your needs. Do not be tempted to buy cheap. You need a calibrated wrench which keeps consistency or the whole point of torque/accuracy is lost. I have used Norbar, Wheeler and SnapOn and had no complaints with them other than the price (a little eye watering for the Snapon)..
Adjustable wrenches normally have the setting in the handle. Turning the bottom of the handle increases or decreases the torque value.
The latch on the base flips out on the Norbar to allow torque setting adjustment.
If we take the Norbar Tti20 as an example you can see the base has a latch which must be opened before the base can then turn to desired torque level. The gauge on the handle gives an NM value in white and an inch/lbs in yellow. I use NMs as the Norbar also features a finer scale at the bottom giving you .1NM values as well. Once set the latch is simply flipped back over locking the wrench at your chosen value.
Adjustable wrenches are available in a number of sizes as regards the socket fitting. I select a 1/4inch head as most socket and bit sets have a 1/4″ converter head so that the wrench can accept standard hex and torx bits. You can also buy converters allowing use of bigger sockets should you need them.
A 1/4″ drive in the 1-20NM range is ideal..
Kentucky Torqueage – AKA Using Your Hand!
I have spoken with some extremely experienced people who simply use guess work to torque screws down. Some of them eclipse me in knowledge and experience. I have in the past used guides such as “hand-tight plus a 1/4 turn” myself. The issue I have with that system is that everyone has a different concept of hand-tight. I would not for example allow the Mountain from Game of Thrones to adjust my scope rings to his version of “hand-tight”. Obviously that is a comedic extreme but you get the idea.. Guessing is also not accurately repeatable. If your gunsmith uses his hand-tight and you have to strip the rifle and reassemble to your hand tight there may be a difference which effects accuracy. Personally I like to remove any such uncertainties when it is easy enough to do so.
I have said it before – do not trust any data 100%. Even manufacturers supply incorrect data sometimes. Collect torque data from several good sources before applying it. The data above should be considered a guide to be compared with other sources. It is not an absolute. If you have found some settings that work well for you in your weapon system then please feel free to share below in the comments.