5 Common Martial Art Drill Mistakes

Practice makes perfect, right?  Well, not quite.  If the way you practice sucks, then you will suck too.  This is true for martial arts just like everything else.  The goal in martial arts training is to safely produce situations as similar as possible to the violent situations that the students are likely to encounter.  The reality of martial arts drills is that, without diligent effort, people will unwittingly fall into a number of bad habits for a number of reasons.  These reasons stretch all the way from trying to be helpful to fear, laziness, and lack of creativity.

I've practiced in various schools across states and styles.  I've gone to seminars for even more styles and trained with people from even more schools.  Regardless of where I go, I see people making these mistakes.  

Awareness of these mistakes and the conscious effort to stick to the goal of drills (to develop attributes and skills to assist in dealing with real situations) is all it takes to avoid the mistakes.  So, let's jump into it.

Not Aiming To Make Contact

Sometimes to win, you don't have to do anything

You've probably experienced this.  The drill is to have one person, the attacker, throw a punch at the defender's face, and the defender is supposed to...do something about it.  The attacker then proceed to throw a punch near the defender's face.  Maybe it went off to one side or the other.  Maybe it stopped so ridiculously short as to offer no threat whatsoever to the defender.  This is bad.  

First, for the attacker, they're training themselves to miss.  That's not a good habit.  Second, the defender gets an invalid picture of what an attack looks like.  Third, if the defender still tries to do the desired technique, it's likely to "be a bit off" since the relative position of the two people is not what would happen in a real fight.

Many times, when I'm the defender in situations like this I'll simply stay still.  I won't move...at all.  When the attacker gets a confused look on their face, as if I was the one that did something wrong.  I'll just look back at them and say, "See how masterfully I deflected your attack using nothing but the power of my mind?"  Usually that gets the point across...at least until they forget and slip back into bad habits.  Sometimes (when we're wearing gloves) I'll stay still on the first repetition just to make sure that they'll hit me if I don't move.  This is not only to verify that they are aiming properly, but it's also to reassure them that they won't break me.  This helps them get over the fear so we can get down to training properly.

Crappy Body Mechanics

Even diligent students will fall into this when they're tired, but it largely comes from a way of thinking that focuses on the defender's execution of the technique rather than the entire scenario.  

I see it all the time when people are supposed to be defending against a hook punch.  The attacker will, lazily, throw a straight armed hook (more of a close-handed slap, really), and the defender will do his thing.  Sure, defending against such an attack is easier than defending a real hook (even a "street fighting" hook), but is that what we honestly expect to run into...anywhere?  Maybe the attacker is being lazy.  Maybe the attacker is trying to make things easy for the defender.  Either way, this kind of thing is unhelpful.

Again, the attacker is training themselves to have bad form.  The defender is training against a straw man of a technique, giving them a false sense awesomeness.  Yeah, you parried every one of those slap punches.  Great.  If anyone ever slap punches at you, you'll be in great shape.

If I'm ever on the receiving end of a bad technique like this, I'll stop the person and say, "Come on.  Give me some energy."  I'll move around a bit, like we're in a fight.  That usually works for a while.  Keep up proper technique is difficult, but it's good for both partners to do.  Stand like you would stand in a fight.  Punch like you would punch.  Kick like you would kick.

Unrealistic Distances

Depending on the particular drill and sometimes even the style being practiced, the distance that the partners start off from each other may be unrealistically close or unrealistically far.  Both are bad.

If the attacker has to take a huge, lunging step to land a punch, then the people should start closer together.  Sure, the extra distance gives the defender the time to do all sorts of things, but realistically speaking an actual attacker will be closer and you'll have less time than in training.  That false sense of awesomeness creeps in again.

Some people will try to combat this by starting off really close together.  If you're working a grappling drill, this might be ok, but if you are doing any sort of striking drill, then there is such a thing as starting too close.  I have a rule of thumb as the defender in drills.  If I can hit you, then I am hitting you.  

This means that if you start off close enough to where I can reach you without moving my feet, then I should be addressing the closeness of my simulated attacker.  This might take the form of an eye strike, shove, groin kick, or whatever.  Once the attacker takes a fighting stance, I'm assuming that the drill has begun.  This trains me to take action when someone close to me takes an aggressive posture.  I fancy myself as a decent fighter, but I don't have super-speed.  If someone is close, then I probably won't be able to block everything they throw my way.  I need that fighting measure, as Bruce Lee called it.

This situation can usually be alleviated by bouncing and moving around like in a real fight and then when the timing feels right, strike.  This will feel much less manufactured than planting your feet at a bad distance and doing the drill from there.

Never Mixing It Up

I've been at schools that only drilled against known attacks.  Even though the set of known attacks was vast, when the time came to do the drill the attack was known before it was executed.  There's a time and place for this, especially when first learning something new.  But, this may come as a surprise to some people, real fights aren't so predictable.

As Hock Hockheim has said many times, we have to avoid becoming drill masters.  Drills are good.  They provide a nice framework for us to learn on, but eventually you should throw that framework away and learn to flow with the situation.

I see this in students all of the time.  We'll work two drills separately: two different attacks, each with their own response.  When we then allow the attacker to choose between the two without indicating which one it will be, the defender will start to hesitate and "mess up."  Well, in a real fight, there are more than two options.  If you train to always know what's coming, how do you think you'll fare in the chaos of a street fight?  If you're honest, you'll agree that things wouldn't go so well.

This drill mistake is usually the fault of the instructor more than anyone else.  Drills should progress towards randomness until they look more like sparring.  The job of the instructor is to recognize where the students are on the spectrum from predictable to random.  Though, sometimes an instructor will allow randomness in a drill but students will settle into familiar grooves and end up being predictable anyway!

Reacting Too Soon

When training in martial arts (especially in self-defense), some degree of acting is required.  I'd rather not have my training partner actually stick his finger in my eyes.  Some techniques have to be simulated and then the receiver must act as if it had really happened (having some experience and knowledge is helpful here).  

Much like the other mistakes, this is a mistake made by the attacker (the person on the receiving end of the defensive technique).  This mistake is particularly prevalent when drilling joint locks and throws.  Picture the scenario: the attacker takes a swing at the defender, the defender blocks and grabs the wrist, grips for an outside wrist lock, and ... before he has a chance to apply the lock, the attacker flips over onto the ground...amazing.

What happened?  The attacker gave the defender the benefit of the doubt and moved as if the lock had been put on in excruciating, violent fashion.  Who does this help?  Nobody.  

First, the defender, again, gets a false sense of awesomeness.  They might be doing the technique all wrong.  They might have an incorrect understanding of how far to move before the lock is "on."  Second, the attacker is training to give in to the technique before it is a foregone conclusion.  There are early, mid, and late phase counters to most techniques.  Giving up early is a bad habit.  

The attacker is also missing out on the opportunity to help refine the defender's technique.  I'm not saying to sit there and have someone crank on your joints hard and repeatedly.  But slowly go through the technique and resist long enough to know that it would hurt/injure you if they continued and went faster.

Don't be afraid of embarrassing someone because their joint lock technique isn't working.  Help them fix it so that it does work rather than help them save face in a safe environment of learning.  I'd rather someone help me save my life than protect me from some vague fear of embarrassment.  If the attacker is worried about being injured from repetitively being on the receiving end of a technique, then slow down and at least feel a little pressure...you won't break.  (If you will, then maybe you need to reevaluate your situation).

Conclusion

Without diligent effort, it's easy to screw up drills.  Don't be lazy.  Don't be afraid of embarrassing yourself or others.  Be realistic about the scenarios you're simulating.  Go at a speed that allows everyone to train safely and effectively.

Ways To Strike With A Stick

(Ok, I know it's been a long time since I last posted.  Other tasks and the holiday depleted my available time and mental energy, but I'm feeling a bit motivated so I'm going to try to crank this one out!)

Having already covered guns and knives, I might as well cover sticks.  There aren't likely to be any surprises here as stick are mainly used as impact weapons anyway.

There are basically three ways to hit with a stick: the shaft (think baseball bat), the tip (think fencing foil), and the butt or "punyo" as some are inclined to say (think reverse grip knife stab). 

These options can have varying degrees of effectiveness and availability based on how you hold your stick.  Different fighting systems that utilize sticks will promote one way of holding the stick over another.  They all have their reasons, and there are pros and cons to each.  Here are some options.

Grip all the way at the end.  This allows for maximum swinging velocity
and "stabbing" reach.  It also avoids certain disarms that rely on the punyo.
The downside?  You don't have a punyo to strike with.

A slight modification of the one above.  This lets out just enough
stick to allow striking with the punyo but not enough to allow
for those same disarms that worry some people.

Moving the hand up a bit more, this punyo is about the width of your hand.
It allows for striking with the punyo as well as hooking limbs and weapons.
In some cases, it can be used to apply compression locks, and yes it puts
you at a slight risk of being disarmed (it's still my favorite grip).

This relatively uncommon grip is not so great for swinging strikes,
but it is excellent for ground fighting.  It can be used to hook, choke,
crush and do some strikes.

Continuing up the stick, you might end up grabbing it so the majority
of the stick is coming out of the "bottom" of your hand.  This
slightly modifies how you go about "stabbing" and swinging the
stick, but you can do the 3 ways of striking just the same.

An alternate grip of the previous grip.
This allows for more control of the tip in
the event that you want to stab someone in the eye.

Two handed grips have a lot of variety.  You can hold it like a baseball bat if it is long enough.  You could hold it like a rifle (one palm up, one palm down...hands near opposite ends or sliding anywhere in between, symmetrically or asymmetrically).  Or you could do a more traditional two-handed grip with both palms down.  With these latter two versions of the two-handed grip, you can't get the swinging velocity of a one-handed grip, but you do gain the shove and two-handed block, which is actually really useful.  You can also get a lot more momentum and structure behind the tip strikes.

Conclusion

So, this article was more of a taxonomy than anything else.  Sticks have always been impact weapons.  So, seeing how to strike with them is not likely to be as much of a creative leap as it might be for pistols and knives.  That being said, there are definitely things to consider about how your grip might affect the quality and availability of the different ways a stick can strike someone.  Think through the different scenarios and definitely mix it up in sparring to see what works best for you.  You might be surprised.

Ways To Strike With A Pistol

In pattern with the recent posts, here's a brief treatment of how to use a pistol as an impact weapon.  Sure, shooting bullets is the primary way to use the weapon, but not all situations allow or call for such usage.  Perhaps you're out of bullets.  Perhaps your gun jams and the bad guy leaps on you.  Maybe the area behind your target isn't clear, and you don't want to risk hurting an innocent person.  Whatever the case may be, there are plenty of situations in which you may want to use a pistol as an impact weapon rather than a projectile weapon.

The Pistol Whip

Anybody who has played a first-person shooter game in the last two decades is probably familiar with this move.  It involves striking with the bottom of the handle.  This is a perfectly natural movement as it is essentially just a hammer fist assisted by a hard object.

The Barrel Push/Thrust

This is when you basically thrust the barrel of the gun into the other person.  You can't quite get the velocity or power that you can with the pistol whip, but it'll hurt nonetheless...especially if you choose an effective target.  Now, this isn't meant to be like in the movies where the bad guy pushes someone with a gun in a way that maintains contact.  This is more like a powerful break in a game of 9-ball.  Hit and retract.  Part of the reason for this is the slight (I emphasize...slight) possibility that if you maintain pressure on the barrel such that the slide moves back ever so slightly, some guns may not fire because the firing pin can no longer reach the bullet.  Like I said, it's rare, but I imagine that if you have your gun out then you want to take every precaution to make sure it does what you want it to, when you want it to.

The Barrel Slap

You can get a bit more velocity on this one than the barrel push.  You swing the barrel of the gun like a little stick and hit the bad guy using any side of the barrel (top, sides, bottom...if you're gun is long enough).  If you hit with the top of the barrel, you might be able to get some bonus damage by raking the sights across the guy's skin.

Purpose/Goal

The purpose or goal of hitting someone with a pistol in any of these ways can range anywhere from just hurting the guy to getting distance so you can get a clear shot off.  It all depends on the situation.  Maybe you don't even want to shoot the guy.  He may have rushed at you thinking you wouldn't shoot, or maybe you hadn't drawn yet.  You slap the guy around a bit with the gun to let him know you're willing to hurt him, you gain some distance, point the gun at him, and then let him quietly ponder his life choices as he realizes the seriousness of his situation.

Caveats

It should be noted that guns are precise machines (some more than others).  Slamming your gun into a hard surface (like a skull) might cause things to get knocked out of place.  So, be ready to clear any jams that might occur afterwards.  My understanding is that semi-automatics, having more moving parts, are more finicky than revolvers.  Perhaps doing some experimentation at a shooting range (they may not like you slamming your gun into the table so going out in the country might be better) would be a good idea.  Another thing to be very careful of is the possibility of your gun going off because of the impact.  Maybe the impact moves that firing pin just fast enough to pop that primer.  All gun safety recommendations are still in effect.  Be very aware of where your gun is pointing.  Your intent might be just to hit, but your rickety old pistol might just go off when you do it.  KNOW YOUR WEAPON.

If you found this article eye opening, then you might also want to check out my similar article on alternate striking methods with knives.

Ways To Strike With A Knife

The ways in which you might cause damage to an opponent when using a knife might seem obvious, but there is more to this ubiquitous weapon than just cutting people.  As mentioned in my previous post, most knives can be used as both an edged weapon and a pointed weapon.  That covers the slashing and stabbing that people associate with knives.  But let's not neglect the potential of the other parts of the knife.

As an example, let's look at my CRKT M16-04Z.

Closed position

"Stay away from me if you know what's good for you" position

Just for reference, the blade is 4 inches long (in Texas, you can legally go up to 5.5 inches).  From end to end, it's about 9.25 inches.  Here's what it looks like in my hand.

If we're not friends and you see me like this,
your day is not likely to improve

As I said, the blade and point are the obvious danger zones of this weapon.  But there are some other ways of striking with it.  For example, look at the part of the handle that protrudes out from the bottom of my hand.  It may not be "sharp" per se, but it's enough of a corner to do some serious damage as an impact weapon.  I'm a big fan of hammer fist strikes already.  So this part of the knife just augments those strikes.  In the Apache Ghost Dog system, striking with that part of the handle is called an "eagle's beak".  If you've ever had, the back of you hand hit in knife sparring with one of these...you know it hurts badly.

Let's not forget that the blade (particularly the one on this knife) is a slab of metal with some weight behind it.  Beyond the cutting/stabbing parts of the blade, hitting someone with the flat of the blade can be jarring and painful.  In sparring, I do this using a whipping motion similar to a back fist strike.  I use it to either hit my opponent's weapon out of their hand or to just do damage to their hand.  It's very fast and gives up a minimum in terms of openings.  In the Apache Ghost Dog system, this is called a "snapping turtle".  When you feel it, you'll know why.  Now obviously, if you have a little blade, this isn't going to be as effective as, say, a bowie knife.  So, know your weapon.

Now, most knives that people carry around these days are folding knives rather than fixed blades.  Just because a knife isn't in the open position, doesn't mean that it can't do damage.

Closed position, in hand

As you can see, I still have the eagle's beak strike available to me.  I also have a similar strike on the other end.  If effect, a closed knife is like a kubaton, which is a small impact weapon like the one below.

Spiked kubaton

You should also note that my knife fits excellently into my hand, weighting it for more devastating punches.

It's not a roll of quarters, but it'll do

So, even in the closed position, I have heavy punches and impact weapon potential for hammer fist strikes on either side of my fist...all before I even deploy the knife.  This can be useful knowledge when faced with a self-defense situation in which you are able to pull your knife but don't quite have time to open it.  Hit the bad guy somewhere painful, and when you have a couple seconds to open your knife, do so.

Conclusion

Knives are dangerous weapons in many ways, obvious and non-obvious.  I didn't mention throwing your knife, but that's a possibility as well.  Though I'm more in the camp of "why would I throw away a good blade?"  All of this is just to highlight the point of my last article that weapons can fit into multiple categories.  So, understand what you can do within a weapon category and you can quickly figure out how to effectively use any weapon that fits into those categories.  In this case, knowledge of pointed, edged, impact, and even projectile weapons will help you to more effectively use knives.

Weapon Taxonomy

There are a lot of different weapons out there. If you include all of the "traditional" martial arts weapons then the variety seems to grow tremendously.  If you want to be as effective as possible in a self-defense situation, then you'd better have some weapons skills, but does that mean that you have to practice with as many different weapons as possible in the event that something strange or exotic is available in a fight?  Thankfully, the answer is a definite "no".

What you should practice with are some weapons that are representative of their entire category.  If you don't know what the categories of weapons are, then read on.

Like the classification of living things in biology, weapons can be grouped (and subgrouped) based on their characteristics.  A good taxonomy will have non-overlapping categories.  So, I'll do my best to meet that standard here.  Keep in mind that while the categories don't overlap, there are weapons that fit into multiple categories.  Not to worry though.  If you understand how to fight with each of the categories, then that multi-category weapon will work just fine for you.

1. Projectile
2. Impact
3. Edged
4. Pointed
5. Flexible

Let's look at some examples.

I love my XDM

Guns are the typical example of projectile weapons, but they aren't by any means the only projectile weapons.  Assuming that stinger missiles and ICBMs aren't in your arsenal, any of the following would also constitute projectile weapons.

Throwing knives...of movie fame

The ever popular "ninja" star

Yes...this is a rock

Anything that you send through the air counts as a projectile.  Let's look at some impact weapons, which are basically anything that you use to hurt someone by running into their body really fast while it's still in your hands.

Here's the typical rattan stick ala Filipino martial arts

Tonfas...like a stick with an extra handle

Nunchucks are good for bashing people...
that definitely counts as an impact weapon

I witnessed the two year old version of my little brother
smash the skull of my older brother with one of these.
It looked like it hurt.  So, this goes here.

The ubiquitous folding chair of pro wrestling fame

And just to make this explicit, you could use a gun as an impact weapon by simply bashing someone with it.  Try not to knock it out of battery or jack up your optics, but...you know...don't die either.  Keep your priorities straight.

On to edged weapons...which are anything with a sharp enough edge to slice flesh open.

CRKT M16 Z ... never leaves my side

"Butcher" knife

Straight razor

A shard of broken glass will cut you as easily as
any knife will

I used a typical knife as the first example because that's what people tend to think of when the term "edged" weapon is used.  However, technically it is both an edged AND a pointed weapon (but nobody really bothers to say that...because it's inconvenient).  Edged weapons need not be pointed and pointed weapons need not be edged.  As we will see below.  Oh yeah, and all these examples except for the glass have impact potential...and they all have projectile potential.  Anyway!  Pointed weapons...

Prison shiv #1

Prison shiv #2

The school yard favorite...

Ergonomic handle for really driving that sucker deep

So yeah, anything that you can stab somebody with counts as a pointed weapon.  If you're really talented, then maybe you could turn these into projectile weapons.

Of all weapon categories, flexible weapons is probably the most neglected.  Or at least, only a very small subset of these weapons have any sort of popularity.  We've already seen the nunchucks, which are a sort of flexible/impact weapon crossover.  But that's just scratching the surface.

Three piece staff ala China

Kusari fundo ala Japan

Flail ala...miscellaneous European countries...I don't know

I actually wear this kind of belt virtually every day.  The
metal doesn't look like much, but I could break someone's
bone with it I'm sure.

Here's the famous Dan Inosanto using a sarong (ala Indonesia)
to make some poor guy's day a little less pleasant

Flexible weapons have a "bendy" part.  They can be used to grab, immobilize, and strangle.  When weighted, they can be used as effective impact weapons as well.

That is about it for categories of weapons.  If you can understand how to use each of the categories, then you should be able to use just about anything that you pick up to defend yourself adequately.  You should be able to improvise just about any object into a weapon of some kind.  Adaptability is key.

I've been thinking a lot about various weapons and their applications in self-defense scenarios.  So, expect to see more along this vein in upcoming posts.

Rock, Paper, Scissors...Stab!

Recently, I saw a video that inspired me to make a new drill for my students.  The video took place in a kendo school.  Two opponents knelt in front of each other.  Between them were two toy hammers and a big bowl.  They then proceeded to play rock, paper, scissors.  The winner grabbed the hammer and tried to hit the other guy's head.  The loser grabbed the bowl and tried to use it as a helmet as quickly as possible.  If a clean shot was landed, then a point was awarded.

Beyond the comedic value of the video, I instantly saw a framework for what will likely be many games/drills at my dojo.  The first of which I will do this Saturday and will proceed as follows.

Two opponents will kneel in front of each other about one and a half arm lengths apart.  In front of them will be two training knives, one for each of them.  They will play rock, paper, scissors.  The winner gets to grab their knife and will have 3 seconds to cut the other person.  The loser must defend through blocking, parrying, and/or disarming.  If the loser gets cut (probably restrict this to vital areas), then he or she has to do 5 push ups.  If they tie, then they can both grab a knife and the same rules apply.  If you lose the rock, paper, scissors battle and you grab a knife anyway, then you do 10 push ups on top of whatever else happens.

I'm pretty sure that's going to be a lot of fun.  I like the drill for several reasons.  First, there's a randomness to it.  Often in martial arts drills, roles are assigned and everyone knows what they're supposed to do and when they're supposed to do it.  It lacks a certain realistic uncertainty.  Even having an instructor call out which person is supposed to attack can lead to some psychological predictions on the student's part because the instructor will inevitably want both sides to get an even number of tries at either role.  The rock, paper, scissors pre-game eliminates all of that.  The students have to be ready to attack or defend at a moment's notice.  Second, because of the uncertainty, there's a requirement to be not only physically quick but mentally quick.  I'd argue that mental quickness is the more important of the two in a fight.

I'm actually quite looking forward to trying out this new drill/game.  I have a feeling that there will be some push ups to be had...

Stopping Power? Physics and Bullets

Being a martial artist, the topic of guns comes up frequently.  When it does, the issue of what caliber of ammo is best usually gets brought up along with the all-too-popular point about "stopping power".  Stopping power is often brought up by proponents of larger caliber bullets (.45 and up).  The argument tends to go along the lines of claiming that the bigger bullet has a better ability to stop a bad guy that's coming at you.  Rather than conjecture about whether or not it's a valid point, let's use some science to figure this out.

First off, let's agree that Hollywood movies do not constitute sufficient evidence of stopping power.  Ridding our minds of the images from movies that bias our thoughts on the effects that bullets have on the human body can be difficult.  That's why we have to let the science and math speak on the issue.

The most relevant physical law at play here is the law of conservation of momentum.  The momentum of an object is calculated simply by taking the product of its mass (m) and its velocity (v), mv.  The law of conservation of momentum basically states that the combined momentum of two interacting objects will be the same before and after the interaction.  To put it in a formula:

m₁v₁ + m₂v₂ = m₁v₁' + m₂v₂'

Here the apostrophe after the velocities indicates the post-interaction velocity of the given objects. 

 An example of this type of interaction might be a bowling ball hitting a bowling pin.  Initially, the pin has zero velocity and the ball is moving at some speed.  After they hit, the pin is now moving (in the direction perpendicular to the tangent of the ball at the contact point) and the ball has slowed down somewhat.  If this didn't happen, then the ball would just smash through the pin, the back wall and whatever was behind that...like the Juggernaut.

I'm the Juggernaut!  Once I start moving I can't be stopped!
This is bad for science but awesome for action scenes!

In much the same way, we can look at a bullet hitting a human being and what effect that might have on his momentum.  In other words, we can use the above formula to calculate just how much a bullet will slow someone down.  Cool, huh?

Now, the was to affect momentum as much as possible is to have a "sticky" interaction, which means that the two objects stick together when they hit each other.  A bullet that passes right through a guy isn't going to affect his momentum by much.  So, let's assume that the bullet fully embeds in the bad guy (of course the target is a bad guy...we only shoot bad guys...right?!).  I'm also going to make a bunch of other assumptions that will only help the "stopping power" argument.  Like I said earlier, people who argue for stopping power tend to carry .45 caliber and up.  Let's look at some stats on the .45 ACP round:

mass: 230 gr (15g)

velocity: 270 m/s

That's not too shabby.  But for the sake of this exercise, let's assume that our hero's pistol fires .50 BMG bullets.  (That's the big one in the picture below.)

The stats on this bullet a bit more impressive:

mass: 800 gr (52g)

velocity: 882 m/s

Enter the bad guy.  The average weight of a human male in the USA (according to wikipedia) is 195 lbs, but we're going to say our bad guy weighs only 150 lbs (68 kg).  Let's say that the bad guy is charging at our hero.  Now, this morning I ran 1.4 miles at about 3.5 m/s, which is NOT fast and certainly wouldn't qualify as an attacking speed.  So, let's assume that our bad guy is not only small but also slow, traveling at a mere 3 m/s.

To summarize:

The bad guy:

m₁ = 68 kg

v₁ = 3 m/s

The bullet:

m₂ = 52 g = 0.052 kg

v₂ = -882 m/s  (negative because the bullet is going in the opposite direction as the bad guy)

Post-impact (sticking together):

m₁ + m₂ = 68.052 kg

v = ?

We want to use the above formula to solve for v.  (Who's up for some algebra?)

To substitute in the values that we know...

68 kg (3 m/s) + 0.052 kg (-882 m/s) = 68.052 kg (v)

158.136 kg m/s = 68.052 kg (v)

which means...

v = 2.33 m/s

v is positive, which means that the bad guy-bullet combo is still moving in the same direction as the bad guy was going before the impact.  In fact, a FREAKING .50 BMG bullet that COMPLETELY LODGED into the LOW WEIGHT bad guy was only able to slow him down 2/3 of a meter per second.

I won't bore you with more math, but the results for a more realistic situation involving a .45 ACP bullet and an average weight US male traveling at a typical sprinting speed (9 m/s) would be that the bullet would only slow down the bad guy by LESS THAN 0.05 meters per second.  That's not much given most altercations happen at a distance of less than 6 feet.  

Conclusion

Even if your bullet hits a major off switch, a knife wielding bad guy might still fall on you and cut you if you don't move out of the way.  It doesn't matter if you're firing .22 caliber bullets or a .50 BMG.  Personally, I carry a 9mm because it has MORE BULLETS.  With more bullets, I can shoot more bad guys or lay down some cover fire to allow me or someone else to move.   Many people will swear by their preferred caliber, and they may very well have their reasons.  Just don't let "stopping power" be one of them.

Springfield XDM 9mm Compact
19 bullets using the full-size mag...19!!