What is "keyholing"?

[KMAX]

This is a newbie question, no doubt, but what is "keyholing"? It is not a term I am familiar with. Maybe I call it something else. Thanks.

[Brian Pfleuger]

Keyholing is when the bullet goes through the target sideways.

[KMAX]

Thanks Brian. Knew I could count on somebody to answer my question right away. Lot of knowledgeable people here at TFL. Thanks again.

[bcarver]

bullets flying sideways or tumbling. It is caused by instability in the bullet. I think the most common cause is improper rifling twist rate. I have never seen it occur. Most guns are designed for the most common rounds. If you are shooting a heavy or light(for caliber) bullet you may encounter it. The bearing surface of the bullet (length that engages the lands) is a factor also.
The rifling stablelizes the bullet by imparting spin(like a football). Not enough and the bullet wobbles.

[Glenn E. Meyer]

It is well known in short barrel guns. For example, the NAA minis are notorious for keyholing 22 level rounds.

Seen it myself. I've even seen a perfect sidewise 223 puncture in card board. How did that happen? Who knows.

[KMAX]

Is this where the idea of the M16 bullets tumbling came from?

[44 AMP]

Is this where the idea of the M16 bullets tumbling came from?

No. "Keyholing" has been seen since we switched from round balls to bullets. (because, obviously, if a round ball goes through the target "sideways", how do you know? )

Bullets too long for the rifling twist rate they are fired from, OR bullets undersize to fit the rifling properly can, and do keyhole. The bullet tumbles in flight. If it happens to hit the paper end on, we seldom notice, but if it hits the paper sideways, its obvious. The oblong, generally bullet shaped hole reminded folks of a keyhole in a door, and so the name...

The M16 bullets "tumbling" occurs only AFTER the bullet strikes, NOT when its flying to the target.

FYI, virtually all rifle bullets will "tumble" after striking flesh. This is because the base is heavier than the nose. What differs between them is the amount of tissue they travel through, before the tumbling happens.

The M16 round tumbles in a very few inches, .30 caliber rounds "tumble" (yaw) somewhere after a foot, or a foot and a half, or so. Calibers for really big game will penetrate several feet of animal (and heavy bone) before the yaw becomes a factor (or is even noticeable in some cases).

There are a lot of variables but essentially, most of the time we don't see the tumble in tissue in bigger calibers because the bullet has exited before it tumbled. And, soft point, expanding type bullets do their thing, totally changing the "tumble" factors that a bullet that keeps its long pointed shape has when moving through tissue.

While there is some basis of fact for the "horrific wounds" from M16 "tumblers", I believe that the truth was "embellished" to Vietnam GIs, in an effort to give us confidence in the new and radically small bore rifle. And no matter how much or how little truth there is in a story like that, once it goes into the troops hands, it almost never goes away, and only rarely gets corrected.

[CWKahrFan]

I inherited (lucky me) one of those cheap Rohm .22 snubs that tumbled EVERY shot... At about 6 ft. out of the barrel, the slug would start whirring loudly... like VVVRRRRUMMMM... and arcing downwards... and the target showed keyholing on every shot.

[mete]

Handguns with a leaded barrel often show keyholing.
The 223/5,56 have been made with various twist rates from 1:12 to 1:7 .The 1:7 for the very long military bullets. It is the length not weight that tells you what twist you need.

[STEINER]

44AMP...
Your post explains something that I always wondered about.

What has always been confusing for me is if you are in combat, boots on the ground with a rifle and your goal is to stop the enemy, why not cartridges that do the most leathal damage.
I know the "Geneva Convention" doesn't allow hollow points but doesn't that defeat the soldier's objective?

[Buzzcook]

I know the "Geneva Convention" doesn't allow hollow points but doesn't that defeat the soldier's objective?

The objective of a soldier is not to kill enemy soldiers. Killing enemy soldiers might be needed to achieve that goal, then again they might not.

[Tinner666]

What has always been confusing for me is if you are in combat, boots on the ground with a rifle and your goal is to stop the enemy, why not cartridges that do the most leathal damage.

We were taught to only wound the enemy. War is about economics, not killing and ammo is made to be more humane and injure more than kill.
That's one reason so much is made about the number of shots fired versus the number killed.

[Toolman]

My grandfather gave my brother a Winchester WRF pump .22 that had the barrel split about an inch from the muzzle. Brother cut it off and filed the end. He shot it and it keyholed terrible. I asked him if he re-crowned it after cutting off the barrel. No, he didn't. He had a local gunsmith crown the barrel & it pretty much fixed it. If you don't have a good crown, the gases aren't equal around the bullet when it leaves the barrel & that can cause tumble.

[Glenn E. Meyer]

Interesting:

1. All the service personnel I know say they weren't taught to wound but obtain good hits. Let's see a service manual that says shoot to wound.

2. Hague Convention - not Geneva.

[44 AMP]

What has always been confusing for me is if you are in combat, boots on the ground with a rifle and your goal is to stop the enemy, why not cartridges that do the most leathal damage.
I know the "Geneva Convention" doesn't allow hollow points but doesn't that defeat the soldier's objective?

It seems confusing, to those who think only in terms of reality....

First off, specifically it was the Hague Accords that (among other things) dealt with hollow points, dum dums, etc. The Geneva convention(s) covered more general things like identification of, and treatment of combatants, prisoners, etc. Most folks only know about the Geneva Convention due to its frequent mention in movies, etc.

The idea in vogue at the time, and remember that this is in EUROPE, where the idea that warfare had rules, and should only be fought under those rules, was that things that caused "unnecessary harm" to soldiers should be banned.

The objective of a soldier is to carry out their orders. Shooting, killing, wounding the enemy is only ONE method of getting that job done. The people making the treaties were NOT the ones doing the fighting, and had no personal stake in survival on the battlefield.

In fact, I would go so far as to say that unlike previous leaders, they were taking great strides in showing concern for those who actually did the fighting, by setting out terms and conditions for treatment, and proscribing certain things that would cause "horrific" wounds.

The fact was, that what they prohibited was seen as those things that made war more deadly, so they were, in effect, trying to make it "safer" for the troops.

The fact that denying these things made the soldiers job more difficult was not a concern.

Also note that while the US was not a signatory nation to the Geneva or Hague accords, we made the official decision to abide by them, back when the ink was still wet on the signatures.

[carguychris]

In addition to what Glenn and 44 AMP have said...

Expansion is the enemy of penetration. Don't forget that one of the main reasons for using expanding bullets for LE and civilian SD applications is to reduce penetration, thus enhancing safety for bystanders beyond the intended target, or on the other side of a structure near the target in the event of a miss.

OTOH for most military applications, Penetration is Good, because (a) any person standing close behind an enemy soldier is likely to be another enemy soldier, and thus worth shooting as well, and (b) modern military firefights often involve digging an enemy force out from behind cover, so it's beneficial for military bullets to retain their killing power after passing through bushes, walls, fences, unarmored vehicles, etc.

Although a yawing bullet may also yaw as it passes through an intermediate barrier, I surmise that most yawing military bullets probably remain relatively more lethal than a hollow-point after passing through barriers like interior walls, heavy vegetation, wooden fences, or light vehicle bodies.

[As a footnote... prior to the advent of modern expanding bullets, many authorities pooh-poohed 9mm as a defensive caliber because 9mm FMJ ball penetrates like crazy. OTOH many military forces had adopted it precisely because it penetrates like crazy!]

[TimSr]

I had an old 7x57 Mauser that put footballs on paper every time I could actually hit the paper. Rifling was shot out of it. There was a reason they used round balls in muskets!

[Skans]

Keyholing is usually an indication that the barrel has something seriously wrong with it - either shot out (rifling worn) or something wrong with the barrel's crown.