Yama-BP-JSerio-SPC

[bettingpython]

I never mess with a dealer on private sale. I don't even want a receipt because I don't want the guy to remeber me. FTF sales break the paper trail. The only thing I ask someone before selling ftf is if their is any reason they can't legally own a firearm. That's even more due dillegence than is even required.

[wladziu]

Knock-down power does exist.  I've done it.  I'm not talking about big game or paper. 
The problem comes in when you try to find a person dense enough to absorb the round momentum while allowing as little penetration as possible, or finding a large enough BOOM!  Fat people don't count, unfortunately.  Best shot placement I've had for knockdowns was the hip.  And as was said, don't expect a handgun round to do much of anything.  Unless shot placement is right on, you're only achieving penetration.  I've experimented with knee shots, liver, chest, shoulders, legs.  A good headshot is always appreciated, but very hard to practice.  To add to the "wobbling" difficulty of headshots (and it's amazing how much that people actually wobble their heads), though, you have to consider shot placement actually on the cranium.  Anything lower than the eyes, and you're just getting gristle. 
Knee shots never worked well for me.  There's still alot of crawling involved afterward (and at a surprising rate), even with direct hits.  Shot volume is a priority, especially with subjects moving at a good clip, and leading becomes an issue.  My tip is to aim at the patella, not behind (the ligaments and joint heads) if given a side presentation.  If given a full frontal, knee shots are not recommended because of clothing, unless they're wearing shorts or you're happily armored.
Abdominal shots are worth nothing.  Especially defensive.  I've tried the classic liver shot (like I said), lungs, diaphragm, and yes, I've tried the heart.  Heart shots are better than you might expect, but certainly not the classic movie speed.  Subject expiration is quicker than, say, suffocation, but certainly not immediate.  Crawling does occur.  Lungs shots are absolute garbage; they can still run.  One of my best, though, happened to be the diaphragm.  While not an immediate kill, of course, some stoppage did occur.  I found it very strange, but I guess I could relate it to a punch in the gut with the air getting knocked out of you.  They didn't really "stop" per se, but there was usually stumbling.  On one occasion, I was pleased to see a subject fall to the knees (but, got back up). 
Neck shots are incredibly, incredibly difficult. 
As was mentioned, fragmentation does do immediate damage, but movement still occurs.  You'd be surprised how much.  It mostly depends on the munition, it's shock effect, and the constitution of the subject.  NEVER EVER expect ANYONE to stop.  Most don't. 
I wasted a belt and a half on an individual no taller than 5'8", no heavier than about 150.  Midsection shots within the upper gastric to lower illiac sections (think of the abdomen in 9-section quadrants, lumbars on the side, gastrics on the top, iliacs being upper pelvis), leaving the satisfying "pink-mist" effect.  Individual still ran like an Ethiopian chasing a chicken. 

The human body doesn't lend itself well to absorbing ultra-high momentum of small projectiles.  The best I've found (my point) are side presentations with the high(er) probabiilty of a spinal shot with the larger back muscles, when using smaller than .50 caliber.  Femoral shots are absolutely awesome, given the high density of that particular bone.  But, weird physics comes into play there.  Rounds sometimes tunnel along the side of the bone, or fragment without shattering the bone itself.  Stumbling happens there, but is easily overcome by determined individuals.  Same thing with shoulder hits, usually deflection occurs. 
Do not be swayed by the belief that a large person can take hits better than a shrimpy guy.  It's absolutely not true.  The physics may show it, your experience with paper may show it, hunting, etc, etc.  But, I'm telling you...   Try it yourself, and see what happens.

After my experiences, I no longer own a firearm.  The sense of security that they give is completely overrated.  I've stopped a 6'8" 300lb guy with riot-controlling sound-ray equipment faster than I've stopped Napoleonic guys (damn near teenagers) with 7.62.  I've seen a normal guy take a full clip of 9mm to the back, point blank, without stopping to flinch. 

Firearms are overrated.  If you need defense, then stick them to the wall with flichettes, move to a better neighborhood, or do whatever you have to do.  Just don't trust something that punches holes, please.  If you absolutely need to stop somebody, please try to achieve optimal "shock effect" and not pain or wound depth.  For this, you need larger caliber than what you can buy without a class 3. 

I respect your $20k in ammo.  Those are fun days.  I had a $125K day, once.  It was a "blast".   Haha.