As a matter of fact, I'm setting up to build 9mm rifled barrels right
now. I'm using my CHNC lathe and a high pressure car wash pump to set
up gundrilling. Then a rifling button to press through the honed
barrel for the rifle grooves.

Even doing things on the cheap, I'll end up spending $500 to make the
first barrel. probably not worth it for one.

Green Mountain rifle company sells barrel blanks. You might look into
that. http://www.gmriflebarrel.com/search?searchvalue=.17

Karl