By the way, Joe is right. Looking at .020 on a micrometer or vernier caliper will scare you.
For those who don't always have a vernier caliper handy... I used to set the points gap on my '69 Chevy truck to .016" with a paper mathcbook cover as a feeler guage. This needed to be done about once a month because the distributor shaft was rough.
So lay a blonde hair on a paper matchbook cover and you are looking at about .020" That's not a lot of material between 8000-12000 psi of hot powder gasses and your fingers and eyes. I spent about a half hour totally blind from a head seperation on a rifle cartridge, so excuse me for being a bit gun shy when it comes to thin barrels. That was a very long half hour.
