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Guns & Ammo Network


Understanding Barrel Bedding

by Jon R. Sundra   |  September 23rd, 2010 6

A rifle that is bedded with pressure on the barrel from the forearm tip is likely to shoot to different points of aim if it is rested between shooting sticks or against a tree or if a bipod is attached to the fore-end swivel stud. That's why the author prefers laminates or synthetic stocks and full- or partial-floating barrels.

There are many factors that affect accuracy, but next to the barrel itself, none is more important than the bedding dynamics between the stock and the barreled action.

Actually, “accuracy” can be looked at from two different perspectives: pure grouping ability and a rifle’s ability to maintain zero. The two are not the same. The former is the measure of how tight the average group measures, regardless of where on the target it is, while the latter is where our point of impact (POI) is relative to where we expect it to be. In a hunting rifle, consistent POI is more important that pure accuracy, and it’s primarily a function of the bedding.

There are a number of ways a bolt-action rifle can be bedded. Bull barrels and heavy varmint/target barrels oscillate less violently than sporter-weight ones as a bullet accelerates down the bore and generally shoot just as well when free-floated as they do when bedded. Some competitive shooters, however, have been known to glass-bed the barrel and leave the action floating while others permanently bond the barreled action and stock together by not using release agent. Most sporter, carbine and ultralight hunting rifles, however, respond better to other bedding dynamics.

Injection-molded stocks are unsuitable for glass bedding and generally have hollow fore-ends that further preclude the process. Note the small, circular pressure pad at the tip. Laid-up stocks take to glass bedding well.

Generally speaking, the thinner the barrel, the more likely it is to group best with some dampening pressure being exerted by the stock. The easiest way to produce this dynamic on a production scale is to hog out the bottom of the barrel channel about 1/8 inch deeper than necessary to a point about one inch from the fore-end tip where a raised band of material is left remaining. It is this raised portion of the channel that is the only contact between the barrel and stock. When the forward guard screw is cinched up, the stock is actually bowed inward, and that is what produces the tension against the barrel.

Dampening barrel pressure can also be exerted the entire length of the barrel channel, but to accomplish that you must have perfect surface contact the entire length of the forearm, and that can only be achieved through glass bedding, something no production rifle-maker does. Some, however, do apply epoxy to the recoil-lug area of some select models.

This full-floating barrel will remain perfectly centered in the barrel channel of this laid-up fiberglass stock. Were it a one-piece stock of walnut, the gap between metal and wood would probably change between seasons or if subjected to a drenching.

For a rifle to group its best and maintain zero, the pressure dynamic between the barrel and stock must remain constant, particularly in the case of lightweight barrels that are being dampened only at the fore-end tip. Traditional, one-piece stocks of walnut have proven to be fairly good at keeping this pressure relationship constant, providing the grain structure is properly oriented and the wood is thoroughly sealed not only on the outside but all inletted surfaces as well.

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