what machine/machines do i have to use to make a gun barrell and the spline in it?

Answer 1

Gun barrels like most metal is made by using lathes: http://en.wikipedia.org/wiki/Lathes
The rifling can also be made this way. In fact all the items to create a lathe can be made on a lathe.
The lathe operates by turning the metal stock very fast and then applying a knife against it.

The other metal milling machine is called a metal mill: http://en.wikipedia.org/wiki/Milling_machine
Although not as useful as the lathe straight line cuts are made with them. Once the barrel is cut then the top spline is straight so a mill would have to be used.

CNC Machines; computer numerical control Machines (http://en.wikipedia.org/wiki/CNC) are computerized mills and lathes that are used by industry to manufacture millions of parts a year, probably more. With a CNC machine it is possible for the draftsman to draw the part an then for it to be programed and manufactured without additional human intervention, except to replace the stock.

The latest technique in construction is to use an ink-jet style printer that lays down the part a layer at a time. With this machine a plastic part can be created and then a reverse mold can be made from that so that the metal can be cast.

Casting is the last method needed to create parts for a gun; like the trigger and some other mechanisms that can be cast instead of being milled, but the lathe is the most commonly used machine in metal manufacturing.

Answer 2

You will need a metal lath to turn and bore the barrel. You will need a Broach machine to draw the splines in the barrel called rifling's.

Answer 3

In Texas it must be a minimum of 18" barrel length. The over-all length must exceed 26 inches. ADDENDUM: 3. Manufacturing, transporting, repairing, or possessing a shotgun with a barrel less the 18” and an overall length, butt to barrel, of 26” or a rifle with a barrel less than 16” and an overall length of 26” is considered an unlawful act. H