"Clark Magnuson" wrote in message
...
http://www.6mmbr.com/gunweek055.html

Using EDM to cut rifling is at least 30 years old, although I don't know if
it was ever used in any kind of production (ECM has been used to rifle
barrels for longer than EDM, and it's been used in production). However, I
hadn't heard of using it to cut chambers. I'd like to know what the "patent"
is about.

The description of EDM in that article is about half right.

--
Ed Huntress