If I remember correctly it is something like 60 in/lbs. for action screws.
It's not quite that simple. Here's an column I did on the subject for
Sports Afield magazine a couple years ago:
The first time I encountered another hunter who used a torque wrench to tighten the action screws of a hunting rifle occurred on a Coues deer hunt over 20 years ago. Four of us flew to Hermosillo, Mexico, where the outfitter drove us northeast to an old adobe ranch house in the Sierra Madres. Two of us had removed the barreled actions from our rifles so they’d fit in take-down cases. I put mine back together with a standard screwdriver, but the other guy used a small torque wrench, which he claimed would result in the rifle shooting to exactly the same place as before he took it apart. It did—but so did my rifle.
After thinking this over, as any obsessive-compulsive would, I decided to run some experiments, because I might have accidentally tightened my rifle’s screws the “correct” amount. These tests are still ongoing, partly because of torque wrenches and screwdrivers becoming more popular among shooters, and not just for action screws but scope-mounting.
Along the way I became acquainted with a guy who worked for a company that calibrated torque wrenches, among other measuring tools. He said many click-type torque wrenches and screwdrivers used by rifle enthusiasts go out of calibration after some use, because they depend on relatively small springs. On the other hand, he said, beam wrenches hardly ever go out of calibration, because they’re so simple and sturdy.
The torque driver I’ve used for over a decade now was pretty expensive, around $160 in the Brownells catalog. Others are far less pricey. One popular model sold for about $35 at the time I got mine, but is now up to $50, but some are around $20 (probably why my mine model has disappeared from the Brownells catalog).
I recently compared the calibration of my torque driver with a beam wrench, purchased new at a local auto-parts store. This required considerable experimentation, but it turned out my torque driver is still in calibration—at least according to this particular beam wrench.
This may be because of my driver’s high quality, but may also be due to not using it as often after the first year or two. One early experiment involved how much torque a standard screwdriver created on typical 6-48 scope-ring screws. Mount manufacturers generally recommend tightening 6-48s to 20 inch-pounds, give or take a little. (An inch-pound is one pound of force, applied one inch from the center of the pivot-point, meaning the screw.)
I found that holding a standard screwdriver with the tips of my thumb and first two fingers resulted in around 20 inch-pounds. I mount quite a few scopes, and unless a manufacturer suggests a torque considerably different than 20, use the two finger/thumb method. So far it’s worked, holding scopes firmly but not so much it leaves ring-marks.
I also ran shooting tests with various bolt-action rifles, comparing how they reacted to being tightened with a torque wrench or driver and the method I learned decades ago. More than one gunsmith (and writer) recommended starting the screws into the action, to keep the stock in place but not tight, then hold the rifle muzzle-up and firmly tightening the front screw.
With typical bolt-actions featuring a rectangular recoil lug on the front end of the action, this settles the lug against its stock recess, and keeps there it there while tightening the front screw. Afterward, the rear screw gets tightened enough not to work loose, but not as firmly. (Some actions, including the Model 70 Winchester and blind-magazine Remington 700, have a middle action screw to hold the front of the trigger guard in place. These should barely be tightened; otherwise the action can bend slightly, which doesn’t help accuracy.)
I checked the torque of the slot-head screws on a couple of rifles, and it came out to around 35-40 inch-pounds on the front screws (accomplished with the screwdriver handle gripped with my entire hand) and about 25-30 inch-pounds on the rear screw. This is similar to Remington’s recommendation for Model 700 rifles stocked in wood or injection-molded synthetics, 30-35 inch-pounds for both action screws.
However, Remington also recommends 45 inch-pounds for both screws on their Sendero 700s, which have synthetic stocks with aluminum bedding blocks. H-S Precision recommends 65 inch-pounds for both screws in their bedding-block stocks. So what’s the deal?
The primary point of torqueing action screws is to make sure the barreled action and stock maintain the same firm connection, assuring shot-to-shot consistency—meaning accuracy. (Some shooters make a distinction between accuracy and precision: Accuracy means hitting the intended target, while precision is bullets consistently landing close together, even if they don’t hit the precise aiming point. But when most hunters discuss accuracy, they mean small groups.)
A secondary point of torque involves screw threads, which only take so much torque before they start to deform. When that occurs the screw can loosen during use, resulting in erratic accuracy (or precision—take your pick).
Third, the hardness of the stock can vary, especially wood. The “bottom metal” can also be made of aluminum or steel, and the dimensions actions vary. The tightening method I learned long ago probably originated back when many bolt-actions had relative skinny tangs—the extension on the back-end of the action holding the rear action screw.
Probably the most common skinny-tang action is the 98 Mauser. Multiple millions of 98 actions have been made, and continue to be made, with the 98 also becoming the partial design-base for other actions, such as the 1903 Springfield. The combination of a narrow tang and walnut stock could result in the wood being crushed when the rear action-screw was “over tightened,” also potentially resulting in a loose connection and poor accuracy. This is why many military 98 Mauser stocks included a steel cylinder around the rear action screw.
Many later bolt-actions have very broad tangs, protecting against this tendency, including the Model 70 Winchester, Remington 700 and Ruger 77. The Ruger includes an angled recoil lug, allowing the front action screw to draw it firmly into the stock recess, even if somebody doesn’t hold the rifle muzzle-up while tightening the screw.
Bolt-actions have continued to evolve, with many 21st-century designs lacking the single, front-end recoil lug. Instead they use smaller metal or even synthetic bedding blocks, some designed to fit recesses milled in the bottom of the action. Many also feature “pillars,” metal cylinders epoxied into the stock around the action screws, to help maintain consistent torque and prevent crushing the stock, however slightly.
I also recently consulted three gunsmiths with a reputation for making very accurate rifles—which I know about their accuracy personally, from owning their rifles:
Melvin Forbes, owner of New Ultra Light Arms, said he doesn’t bother with torque settings on his rifles, just tightening the screws until they stay firmly in place. He also only fits one pillar in his synthetic stocks, around the front screw to prevent customers from over-tightening and having the screw’s tip end up inside the bottom bolt-lug recess, preventing the bolt from turning. He also pointed out that in stocks with V-shaped bedding blocks to hold round actions, over-torqueing can bend the action slightly.
Mark Bansner, head of Bansner & Company LLC, said he’d recently done some torque tests, finding that with a standard Brownells Mag-Tip screwdriver and either hex- or Torx-head screws, tightening them as hard as possible results in around 60 inch-pounds. He’s not fond of pillar bedding, both because his synthetic stocks are very solid through the action area, and because he’s seen pillar-bedded hunting stocks break at the grip—right where they were drilled-out for the rear pillar.
Charlie Sisk of Sisk Rifles also thinks about 60 inch-pounds works for modern rifles with solid, uncrushable stocks—especially the chassis STAR stock he makes, where the action area is solid aluminum. He pointed out that many if not most hunters either torque action screws way too much, or not enough—the last often due to neglect. Often over-torqueing occurs with individual hex or Torx-head wrenches made of a bent length of steel, because they have long “handles.”
All three gunsmiths mentioned that no matter the specific torque that works for your rifle, you should check the screw-torque periodically. They’ve all had customers bring in rifles that had “quit shooting.” Tightening the action screws fixed the problem.
A consistent action/stock connection is the entire point, the reason my most accurate rifle doesn’t even have action screws. It’s a 6mm PPC benchrest rifle built by now-retired gunsmith Arnold Erhardt, with the Remington action epoxied into the synthetic stock, so I never have to check the action screws!
