you only need a go and nogo gage. the field isnt neccessary.
there is no shortcut around this. only thousandths of an inch turn a rifle from a rifle and into a bomb.
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...
"I crapped my pants to avoid the draft!!" -Ted Nugent