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Bedding And Rifles
#1
Subject: Bedding (Long)

Posted By: ML - Registered User

Posts: 266

Posted At: (4/18/02 6:17 pm)

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(The following stands partially as a response to Mr. Roberts’ question of 11 April, 2002, [see link here] [url="http://pub1.ezboard.com/fhoodlumsweaponsprimitiveandmodern.showMessage?topicID=647.topic"]http://pub1.ezboard.com/fhoodlumsweaponspr...picID=647.topic[/url]

in which he asked an intelligent question about rifle bedding. Several Forum members replied, some with correct information, others with information which required a little clarification. Forgive my tardy response, but it’s taken me a while to compose what I hope will be a thorough and helpful read. So, settle back with your favorite hot or cold libation, because your old Uncle ML is going to ramble on for a bit.)



Bedding and Rifles



No matter the endeavor, man seems to always seek an advantage. How can I make fire more efficiently? How can I throw this rock a little farther? And, in our case here, how can I make my rifle shoot more accurately?



To that last point, the topic of "bedding" often comes up, and justifiably so. Bedding, per se, is concerned with how the metal parts of a firearm come in contact with the stock. In general, we’re concerned with two areas: a rifle’s barrel, and its receiver or action. Let’s take a look at what goes right, what goes wrong, and what we can do about it.



A rifle’s stocking generally serves to make the unfriendly metal of the weapon more ergonomically inviting: i.e., as a glorified handle, it gives us a place to hold on. In some instances, it may also serve as a structure integral to the weapon itself. For example, in the Remington Nylon 66 family of .22 rifles, the one-piece stock forms an integral part of the receiver; also, older firearms, especially sidelock percussion guns of Civil War vintage, use the stock as an essential structural element--the lock and the barrel both mount separately to the stock.



We’ll consider the stock/receiver interface first.



Not all firearms join the stock and receiver in the same way. Look, for example, at a typical lever-action rifle and a typical bolt-action rifle. With the lever gun, we see the stock only joining the receiver at the receiver’s very rear, and only gripped via a pair of tangs which project from the back of the receiver proper. With a typical bolt gun, the receiver lies in a deep groove in the stock (or bed, if you will), like a hot dog in a bun, although here, too, there are exceptions.



This wood-to-metal fit, as other Forum members have pointed out, is critical. If it is too sloppy, the action will flop around from shot to shot, and as it moves, the stock’s structure will contact different parts of the action with different pressures. In addition, particularly with heavy-recoiling arms, the action will batter a loose-fitting stock and eventually split it. If the wood-to-metal fit is too tight, the action will be stressed and bent before a single shot is fired, and this too is detrimental to accuracy.



So, what to do? In the old days, skilled craftsmen working with fine-grained walnut stocks, sharp-edged scrapers, and lamp black produced gunstocks which fit their actions perfectly. Ah, but they had the skill, and labor was cheap. Today, high-speed pantographs hog out generous troughs in questionable wood, the ill-trained wage slaves spend only seconds fitting action to stock in the spirit of mass production. Consider, though, that even a poor working stiff such as yours truly can purchase a truly fine rifle for less than a week’s pay, whereas in the hand-fitting days, firearms were the privilege of the upper classes exclusively--maybe this mass-production stuff ain’t such a bad idea after all.



So while metallurgy and affordability have made exceptional strides over the last century, attention to proper bedding has suffered.



Sometime between 1920 and 1950 or so, this country produced a fine generation of handymen, people who could rewire a lamp, fix their own automobile, and engage in gunsmithing beyond simply swabbing out a bore. These men could run a lathe (wood or metal), weld with gas bottles or an electric arc, and understood about refinishing wood. Sadly, they are old or gone now, replace by and large with a generation who keep their tools in a drawer in the kitchen rather in a well-equipped basement or garage shop, and that’s if they have any tools at all.



Those old handymen discovered many ways to improve their firearms, often requiring little in terms of cash outlay. Correcting poor factory bedding was a fine place to start.



If a stock is too tight in its relationship to the receiver, it’s a relatively simple matter scrape or pare away the wood in question. But what if a stock is too loose? Or, as is most often the case, too tight in some spots and too loose in others? And what to do if the stock is high-centered, and when one tightens down the front and rear action screws the poor receiver bends as though it’s been placed on a medieval torture instrument like The Great Wheel?



Enter the age of synthetic bedding. Gunsmiths discovered that by relieving the stock around the action and then introducing some sort of synthetic bedding material, they could get a perfect, stress-free stock/action fit without much trouble. Various media is applicable here: fiberglass in resin (the so-called "glass" bedding), metal-filled epoxy, even automotive body compound ("Bondo"). The goal is the same: to produce a stock-to-metal fit with no high spots, no low spots, no voids and no pressure points.



Some actions react more favorably to this than others, and every action has its own peculiarities. The Remington 700 family, with its tubular-steel action-body construction, seems happily tolerant of indifferent inletting, and ironically, its shape, initially chosen for ease of manufacture, makes it easy to inlet for as well. Mauser actions, with their flat bottoms and integral recoil lugs, require a bit more care, but produce rewarding results. Mausers, too, require deliberate attention to the area around their stout magazine boxes, as these act as giant secondary recoil lugs, not true with the pressed-sheet mag boxes of more modern Winchester or Remingtons, but Mausers reward this attention, too.



It’s not my intention to provide how-to, step-by-step glass-bedding instruction here: Different actions require different tricks, the M1 Garand in particular. However, in general, the drill is the same, and here’s a greatly simplified version: Relieve enough stock material to provide room for the bedding compound, apply some sort of release agent to the action so you don’t glue it in place, apply the viscous goo, set the action into the stock, let the goo harden, remove the excess, reassemble the rifle, and enjoy the potential for enhanced accuracy.



Please note that synthetic bedding will no more make a well-made rifle shoot better than new sparkplugs will make an already well-running automobile run better. Unfortunately, as we’ve observed, many rifles today can use help.



Forum Member Vector mentions "pillar bedding." This applies specifically to bolt-action rifles with two screws joining the barreled action to the stock, almost always through the floorplate/triggerguard assembly. Two thick, hollow pillars are inserted into the stock where the two action screws are located; the screws themselves fit through the hollow center sections of these pillars. If these pillars have been installed correctly, the surfaces which contact the bottom of the receiver have been perfectly matched.



Pillar bedding is fast and easy, and may help some bedding problems. It does nothing to alleviate poor lateral bedding, and will not eliminate a "high-center" condition. It does greatly help with consistent torque values when assembling action to stock. It’s clearly better than poor conventional bedding, but not as good as the best bedding, be that hand-fit or synthetic.



And an aside: Synthetic stocks neither warp nor swell as do wood stocks, but their bedding may be no better. In fact, inexpensive plastic stocks are often inlet very poorly, and may evidence extremely poor bedding. Again, the solution is synthetic bedding.



In the last 20 years, we’ve seen a metal-to-metal type of bedding, which may produce very good results. H-S Precision riflestocks are a fine example of this (see site below).



http://www.hsprecision.com/stocks.htm



They build an aluminum bedding block into their stocks, in theory offering a perfect action-to-stock fit.



Another similar strategy, taken even further, is in the form of Accuracy International’s complete metal chassis (see link below).



http://www.accuracyinternational.com/aics1.htm



In this latter system, the rifle’s action bolts to a machined metal chassis, and the "stock" is merely a convenient and user-friendly handle, similar in concept to the slab-side grips on your M1911 .45 Auto pistol.



Ready for a stretch? Because here comes chapter two.



Barrels: Bedding and Floating



Barrels are the second part of this bedding issue. Or, probably more correctly, the absence of bedding. You see, when a shot is fired through a barrel, a lot goes on which is not visible to the naked eye. The barrel winds up and cracks like a whip. The barrel resonates and rings like a tuning fork. And the barrel gets hot, and grows in both diameter and length.



First off, you’ve got to understand that very few rifle barrels are really straight, and even fewer are manufactured straight to being with. I’ve had the privilege of standing in the old Mauserfabrik works in Oberndorf am Neckar and examining their 130-year-old turret-handled barrel-straightening press. With skill, a crooked barrel can be quite successfully straightened, and with a high degree of accuracy. When the barrel gets hot, though, it may tend to "walk" in the direction of the original bend. Even if a barrel has not been straightened, stresses incipient in the original manufacturing process remain. So-called "cryogenic" treatment of barrels claims to address this, but I remain very skeptical. Two things do seem to mitigate this warping, though: more barrel mass (diameter), and the hammer-forging process of rifling a barrel.



Nevertheless, even big, fat, stiff barrels as well as hammer-forged barrels heat up, whip, and resonate, although often to a lesser extent, or I should say more correctly to that last point, at a lesser frequency.



Anything pressing against a barrel’s surface tends to interfere with these movements, and as the barrel heats often makes a bad situation worse. Hence, barrels are often "free floated"; that is, the stock material is relieved all around the barrel so the barrel and stock do not touch at all. You don’t need much room--just a couple thousands of an inch (the thickness of a dollar bill or a business card) are enough. And the best results are often found if the chamber area of the barrel is well bedded for the first two inches or so, and the rest of the barrel floated.



Clearly, junk touching the barrel does little good. Hang a bayonet off the end of your barrel, and the accuracy will take a wild shift, guaranteed (note that some enlightened designs attach a bayonet without contacting the barrel at all). Likewise a "clip-on" bipod which attaches to the barrel rather than to the stock. Gas pistons hung off the barrel such as the M1 Garand’s don’t help much either, nor do the handguards of the M16 family (target shooters have come up with a free-floating handguard for this particular weapon). Lever guns often suffer from having a magazine tube banded to the barrel and the forend hung off that. Those gorgeous Mannlicher stocks you see on European carbines? You’ll never see them on a serious target gun. Fluting a barrel does not make it any stiffer than a barrel of the same diameter, but will make it lighter, and consequently stiffer than a smaller-diameter barrel of the same weight, while also increasing surface area.



There are a couple of exceptions to this free-floating scenario, though. Since a barrel surges like a rung spring, and a light barrel surges worse than a heavy one, a little damping may often help accuracy. This damping takes the form of forend pressure--a small pad of material between the forend of the rifle and contacting the barrel’s underside. Such "preloading" of the barrel acts exactly as the shock absorber in your car, or as a finger applied to a tuning fork or a rung bell, damping out the barrel’s surge and resonance. How much pressure to apply? This is another case-by-case scenario, although about seven pounds seems to produce good results with most sporter-weight barrels. How to arrive at that figure? By altering the height (thickness) of the forend pad contacting the barrel. Bed the action first, and then alter the height of the contact pad to fine-tune.



And for every rule, there’s an exception: Many rifles chambered for the .22 Rimfire using very, very heavy barrels may actually shoot better if the barrel is completely contact bedded and the action is free-floated, a common case with the popular Ruger 10/22.



Please remember, these aren’t miracle accuracy cures--it’s just a matter of setting things right, and putting an action and stock together the way they should have been assembled in the first place.



* * * * *



Got an old rifle with a wandering zero? Groups aren’t as tight as you’d like them to be? Check your bedding, and if you find it deficient, then by all means do something about it. But keep your eyes open to the whole package. My brother, who’s hunted hard with a .270 Winchester over the last 20 years, recently went on a once-in-a-lifetime hunt. Rather than buy a new rifle, he merely gave that old bolt gun a thorough going over, and had the barrel re-crowned. It shot better than new. Big trophy.



Look at the whole picture. Practice the four rules. And good shooting.



--ML

18.iv.2



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Of all the things I've lost, I think I miss my mind the most.


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