Barrel Rifling 2

[asymptote]

Can any Military Engineer please resolve a long held question for an unknowing Electrical Engineer. I have often wondered how the rifling is achived in both small and large bore gun. Indeed how is the barrel bored.
One further question on the same subject is what is the larger mid section on tank guns for?
Asymptote

 

[ornerynorsk]

Rifling is nothing more than spiral broaching. Sometimes the lands and grooves are formed rather than cut.

 

[Executnr]

The raised portion of tha barrel is a bore evacuator. As the round passes it, ports in the barrel pressurize the cylinder around the barrel. As the round exits the barrel, the pressure in the evacuator is released by angled ports that point toward the muzzle. The flowing gas from the evacuator pulls propellant gases away from the breach and keeps them from entering the turret.

 

[asymptote]

Many thanks to orneryorsk & Executnr for the answers to my questions. The point about the larger section of barrel has raised many answers from a counter weight, a joint and just a stronger section. I now know.
Regards asymptote.

 

[modesign]

Rifling starts with a simple single cutter drawn through a drilled and reamed tube. This cutter is indexed per groove.A multi headed broach speeds this up by cutting all the grooves at once. A button rifler uses a hardened button with the lands/groove on it and pulled/pushed through an undersized tube swages the bore. Many current barrels are rotary swaged. A mandril with the rifling details on it is inserted into a tube and the tube driven onto it by a powerfull rotary forge.This is often called hammer rifling.
Each system has its advantages, price, speed, quality.

 

[rjmc]

If you watch the History channel, they have a show called "Tales of the Gun", It's about firearms history. They have several episodes dealing with the manufacture of guns. They show the process including the rifling of the barrels. The machines that they use can do half a dozen barrels at once.