La Chasse Au Fusil An Essay On Shooting (An English adaptation of Marolles' original)
Gervis Francois Magne’ de Marolles 1789
http://books.google.com/books?id=-Q0AAAA...ary_s&cad=0 A description of Plain, Twisted, Stub Twist, 'Wire Twist', and Canons a’ Ruban
To form a
(Plain) barrel in the manner generally practiced, the workmen begin by heating and hammering out a bar of iron into the form of a flat ruler, thinner at one end than another, the length, breadth, and thickness of it, being regulated by the intended length, diameter, and weight of the barrel. This oblong piece of metal is then, by repeated heating and hammering, turning round a cylindrical rod of tempered iron, called a mandril, whose diameter is considerably less than the intended bore of the barrel. The edges of the plate are made to overlap each other about half an inch, and are welded together by heating the tube in lengths of two or three inches at a time, and hammering it with very brisk but moderate strokes, upon an anvil which has a number of semicircular furrows in it, adapted to the various sizes of barrels. The heat required for welding, is the bright white heat which immediately precedes fusion, and at which the particles of the metal unite with each other…
This operation, which the English artists term jumping, serves to consolidate the particles of the metal more perfectly…
The mandril is then introduced into the bore or cavity, and the barrel being place in one of the furrows or moulds of the anvil, is hammered very briskly by two persons besides the forger, who all the time keeps turning the barrel round in the mould, so that every point of the heated portion may come equally under the action of the hammers.
The
(Twisted) barrel when forged (is) made to undergo the operation of twisting, which is a process employed by the French workmen on those barrels that are intended to be of a superior quality and price to others; but which as will be seen in the sequel, is very different from that followed by the English workmen in the formation of their twisted barrels. This operation consists in heating the barrel in portions of a few inches at a time, to a high degree of red heat, when one end of it is screwed into a vice, and into the other is introduced a square piece of iron with a handle like an augre and by means of these, the fibres of the heated portion are twisted in a spiral direction that is found to resist the effort of the powder much better than a longitudinal one. To render this operation as complete as possible, it is necessary to observe, that when one the several portions of the barrel have been twisted, the heats that are afterwards given in order to consolidate the fibers of the metal in their spiral direction, by means of the hammer, ought not to be very great. Otherwise the grain of the metal will regain its former state, and the barrel be no better than it was before it underwent to twisting.
More here
http://docs.google.com/Doc?id=dfg2hmx7_216ddsz38cb
(and twisting BARRELS is quite different than twisting RODS that are used to make barrels) but you might like this 