Not difficult. My people were boatbuilders and shipwrights when they weren't farming, and I grew up bending wood. The only hard part is reading the grain of figured wood so you don't crack the stock on 10 grand worth of Perazzi. Straight-grained stocks are pretty wellwellstraightforward.
Build a serious, full-length jig with common heat lamps. The Big-Box stores carry the lamps cheap. This jig is two layers of CDX sheathing laminated together using construction adhesive. Carved, contoured, carriage-bolted oak blocks at both muzzle and action padded by soft cedar shims make for zero slippage of the gun, which is required to protect the bluing. Just dont bend the tubes by overtorquing those nuts. Trigger guards always come off for bending. With the guard off, double check to insure the wrist doesnt have any repairs. Polyurethane and resorcinol glues are the only ones thatll withstand heat. All the others will let go at well below 180 degrees F.including epoxy, PVA, casein, urea formaldehyde and hide glue.
To protect the finish, the wrist is wrapped tightly with several layers of cheesecloth and tied with string. Dont leave any air pockets or the finish will bubble on you. A meat thermometer poked into one of the triggerguard screw holes measures temperature, a pocket watch keeps time, and a teakettle is used to heat peanut oil to just shy of boiling around 200 degrees F. Peanut oil has a high flash point and doesnt smoke, whereas linseed oil smokes and burns too easily.
The jig needs a brace to pull the stock into, and an index to measure how far. Fancy is a plastic grid. Simple is a couple of string lines riding in notches (which are easily moved with a dovetail saw and square when required) and a set of dividers and a rule.
Heat the wrist, keeping the cheesecloth soaked with hot peanut oil. After 20 full minutes at 180-190 degrees, try to bend the stock. Keep heating until it bends easily, some wrists are thicker than others and some wood denser than others. Its the heat that plasticizes the woods cell walls, and it has to reach all the way to the core. For applying pressure, fancy is threaded rod inset into captured nuts let into the brace. Some even saw apart C-clamps to use the components. Simple are padded clamps. Note the C-clamp Im using as an anchor has a scrap of leather glued to it as a pad. Be liberal with the peanut oilkeeping the varnish wet is the only think keeping it from bubbling. Also note there is a hole in the jig base to recover the oil using a pan beneath the bench.
(The reason I use a double layer of CDX for the base is for stiffso I can cantilever the jig onto my workbench using clamps, so as to have the excess oil free-fall into a pan on the floor rather than run all over the bench top.)
When the core temperature of the wood is right, the walnut bends like a wet noodle. Dont force anythingthe wood will tell you when its ready. This one is getting a bit of comb and toe cast, but with this jig you can bend them in any direction required.
No need to worry about springback. Some do spring back a tad over time, some dont. You can always put it back in the jig and bend it further in the direction you began, but undoing over-bends is more difficult and more risky.
Looking at the difference in the bend between photo's #4 and #6, while in the process of bending I release pressure on the clamps to see if it springs back, playing with it a bit until I have the bend I want. Then I remove the clamps immediately after getting the results desiredI dont leave the stock in clamps until it cools. Fewer dents and surprises that way.
Refit the trigger guard, bending it with your hands if you have to. Dont even think about bending a stock with it in place, or you may split out the inletting.
Have at it. Just avoid figured wood until you learn how to read wood grain and have a dozen or so bends under your belt.
Does this have applications to full-length, one-piece stocks like those found on rifles? Certainly.although it is rarely used.
Ideally, one-piece stocks are cut from tree crotches or bends so the wood grain runs parallel to the barrel channel then bends to run parallel with the comb. This minimizes grain runout at the stocks toe (above), preventing weak short grain and the potential for cracking there. But figured wood rarely is found above the crotch in walnut and never in maple, so even the old masters generally ignored the problem and the stock often cracked with age and seasonal movement.
But by roughing out the blank then bending it at the wrist before completing the final shaping, you can have the best of all worlds strength, stability, and figure too.
