SpudFiles

Does anyone know a way to straighten a bent metal pipe, without machinery?

stick a rod in, and pull it up. For thick pipe, a hammer might work. How big is it?

6mm, its for my bbmg I'm working on.

You might want to heat it up first depending on how bent it is

Heat it up, and just keep rolling it.

put it in your vice then squeeze it on every side until you have covered the whole piece of pipe, so that it will straighten it out in a straight line.

What I have thought up is find a drill bit that is a tiny bit bigger and drill a hole in something like a 2x4 and then push the tube threw I think it would work but I never tested it

Depends how bent it is, how long the piece is, how the bend is, and how many bends.
In most cases your going to have to get a new piece if you want a true bore.

Straightening a bent pipe is probably futile ...

But, you might try capping one end, fill with sand then tamp the sand down hard, probably need someithing like a metal rod and a sledge hammer to get enough tamping force. Keep adding sanding and tamping until the pipe straightens out.

This is similar to one way to bend a pipe without it kinking. Fill with sand, tamp, then bend. The sand will keep the pipe from collapsing at the bend.