[PRCalDude]

How are shotgun barrels shaped such that they taper from the breech so that they can fit the entire shell when chambered? I always thought they were made from tubing or round stock and then simply bored through. Is there something else that goes into it?

[Pete409]

The chamber is larger in diameter than the bore itself. The transition from the chamber to the bore is called the "forcing cone". At the forward end of the bore is a taper (smaller) to form the choke.

I suppose all this is done with some type of reamer, but I'm no machinist so I may have the term wrong for that.

[Fred Fuller]

It differs from company to company. Many manufacturers drill their barrels from solid steel billets. Others use rotary hammer forges (Ithaca used to, I think Ruger still does). Internal barrel geometry is established after the initial steps are done- chambering, forcing cone, choke etc.

lpl/nc

[kingjoey]

The chamber is thicker to handle the initial higher pressure. Most firearm barrels are configured that way. Rotary hammering is pretty common since it reduces the machining time/cost and material lost to chip. They'll take a piece of oversized tubing, put it over a center die and feed it through a rotary hammer which will compress the metal to match the shape of the center die. The heat and hammering shapes and strengthens the metal. The Germans were avid users of rotary hammering in WWII to mass produce machine gun barrels cheaply.

[PRCalDude]

If it's drilled from a solid steel billet, that means some sort of hammer forging of the basic shape of the barrel is done beforehand, correct? How is the billet actually formed?