For personal defence the conventional wisdom is 3-7 yrds (21ft) approx. Studies have shown that this is the distance the majority of deadly force engagements take place. The thing to keep in mind is you'll have to defend in court the distance you applyed deadly force. Kinda hard to convince a jury that you just had to kill someone who was 20yrds ( 60 ft) away instead of trying to evade or break contact. Which alot of States require you to attempt. And simply saying " I was in FEAR for my life" just ain't gonna cut it.
The 4 things you have to prove in court is Opportunity, Jeapardy, Ability & Preclusion of the individual attacking you.
Goes back to that mantra of the Military : " Train the way you'll fight"
Real world Personal Defence shooting ( as real as you can make it without someone shooting back ) is about the only way I pratice anymore since giving up hunting.
U.S.M.C.
VFW-8054
USMV M/C
www.usmvmc.orgusmilitaryvetsmcmarion@gmail.com