What makes a gun go KABOOM?!?!?


June 21, 2006, 03:00 PM
I always wanted to know what causes a gun to go KABOOM!!?? One reason i know of is when someone improperly reloads an ammo, but i have heard other people say if there is oil in the bbl it can go KABOOM. Thats one thing that brings a shiver to me sometimes. I dont want nothing blowing up in my hand or something flying towards my face. (Like in "Sin City"). haha

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June 21, 2006, 03:09 PM
It is my understanding that a KB is usually caused by pressures created when firing the gun that are more than the gun is designed to take. I would assume that guns are usually overengineered quite a bit, but when that pressure threshold is crossed, the energy and force has to go somewhere.

Since it's pressure, a lot of things could potentially cause a KB. Improper reloads, definitely--too much juice and the gun could become a grenade. Obstructions in the barrel will ramp the pressure beyond what the gun can take. Gunk in the barrel (grease, oil, lead perhaps) might cause the pressures to be higher than normal. Improper headspace (or a damaged/defective gun).

However, from a completely nonscientific sampling of my memory and various Internet stories, it seems like kabooms are pretty rare if you use the right ammo properly loaded, and your gun is free of defects or damage.

Disclaimer: I'm not a gunsmith or even all that experienced with guns, but I did stay at a Holiday Inn last night. :)

June 21, 2006, 03:51 PM
You never saw the old cowboy movie where the bad guy used his rifle as a walking crutch prior to shooting it, stupid BGs cause KB:neener:

June 21, 2006, 04:34 PM
From what I can tell progressive presses cause KABOOMs.

June 21, 2006, 04:54 PM
There are all kinds of variables that can cause a firearm to "Ka-Boom" as Rumble discussed.

Ammo related KBs is usually is the most common cause. And most of the ammo related ones are from reloads. An overcharged round can cause it but so can an under loaded or "squib" round. In the case of a squib round sometimes the bullet does not make it out of the barrel causing an obstruction for the next round fired. Sticking with factory ammo will help to reduce the chance of a hot or weak round.

Properly maintaining a firearm will also help to prevent a KB. You mentioned oil in the barrel was a concern. A film of oil in the barrel to prevent rust will not cause a KB. Just make sure there are no obstructions in the barrel.

You will find that KBs are very rare compared to the number of firearms in use today. You are much more likely to be injured crossing the street or driving around the block. Combining factory ammo with a properly maintained firearm makes KBs a non issue.

P.S. Please disregard any firearms related information you see in the movies. 99.8% of what you see has nothing to do with reality. ;)

Sheldon J
June 21, 2006, 08:12 PM
I was at my friends gun shop and he showed me his most recient repair candidate. :confused: it was a Cyl from a colt (destroyed by) the owner had bought a "Lee Loader" one of the early small box kits, :uhoh: came with a scoop and dies and you used a wooden mallet to cook your own. :scrutiny: This guy had looked at the instructions and used the one scoop good,:p two scoop's better, :eek: 3 scoops best, :what: method of making his own, at least he did not get hurt.:banghead:

June 21, 2006, 08:29 PM
The oil in the chamber thing is not very common. The issue is that oil in the chamber can cause excessive pressure on the bolt face. Reason being, normally, the brass expands to fit the chamber when the powder ignites and before the bullet dislodges from the mouth. If there is no oil, even a slickly-polished chamber will sort of "grab" the brass. If you have oil and far less surface tension, the brass can slip rearward to the bolt face. There's actually more to it than this, but I'm greatly simplifying the physics involved.

Now, if you have a gun that doesn't have good locking lugs, you might have a nasty bit of fire and metal coming back at you in a generally undesirable fashion.

Of course, LOTS of oil in the barrel would be getting into the realm of, say, filling the barrel with water or something - and the technical term for that is "bad."

June 21, 2006, 08:29 PM
In addition to all the above reasons, one can have a KaBoom! with normal factory ammo should a problem with the gun allow it to fire out of battery -- i.e. with the slide not fully locked to the barrel. Obviously this does not apply to revolvers or low pressure "blow-back" autos like .380 ACP or .22LR.

Over the years I've had more than a few (although its statistically rare, below 1 in 20,000) .22LR rounds cases let go at the rim (where the seam from the sharp bend forming the rim is) and other than making the gun a lot dirtier than normal and making much more noise on that shot, nothing really bad happens -- as long as everyone is wearing eye protection!

Another rare KaBoom! can occur when clearing a gun where a problem in ejection/extraction causes the live round being ejected to go off -- again as long as ones hand is clear of the ejection port and eye protection is in place, no real damage is done.


June 21, 2006, 08:33 PM
Plugged barrels, excessive pressures, defective parts, operator error (using wrong caliber of ammo than firearm is chamber for).


June 21, 2006, 08:33 PM
Finally, guns can go kB when either corrosion, or previously undedected defects in the steel finally give way.

Metalurgical Quality Assurance was my Dad's gig, you have no idea how many things would just go plotz if the steel is out of spec.

June 21, 2006, 09:17 PM
Rembrandt: those are definitely some of the gnarliest KB's I've ever seen-way beyond the usual bulged/ruptured barrel, split cylinder or cracked frame. Exactly how you blow apart the cylinder and the top strap on a Ruger is beyond me. And that rifle; presumably it had a fluted barrel that predisposed it to that nifty blooming-flower like barrel shredding spectacle? Did the guy weld the muzzle closed or what?!?:eek:

Jim K
June 21, 2006, 09:39 PM
With the exception of a hidden defect in the barrel steel or the breech, almost all KBs are due to error on the part of the gun owner, either a loading error or an error such as firing with a plugged barrel. A few may be due to a gun firing out of battery; most designs will not allow that, but some do and it can happen.

As to how to blow the cylinder and top strap on a Ruger, I can say that in a case I know of it was done with a "triplex" load, using three different kinds of powder, including a hefty charge of Bullseye. The shooter had read about that nonsense in a gun magazine and decided to try it.

I think one possible cause of KBs in Glocks and some other pistols has not been explored and that is the 9mm/40 and 40/45 error. This is where the shooter loads a smaller round into the magazine instead of the larger. When the smaller round is pushed into the barrel, it goes too far forward for the firing pin to reach and there is a misfire. The shooter checks, sees no brass, thinks the round failed to load and jacks the next, large, round into the chamber and fires.


Sir Aardvark
June 21, 2006, 10:00 PM
Interesting picture of the Glock 30 kB!

Generally, a .45ACP has a little bit more latitude pressure-wise before there is a critical failure. Of course, no gun is immune to a kB!, even Glocks ;) .

I have not seen it mentioned yet, but one thing that can promote a kB! is an unsupported chamber, like those used in Glocks. Also, some ammo, such as the .40S&W, run very close to critical pressures, so something as simple as bullet setback of just a couple millimeters could be enough to over-pressurize the firearm resulting in a hand grenade.

A kB! can be attribute to a plethora of issues: barrel obstructions, double-charged reloads, heavily leaded barrels, weakened over-reloaded brass, etc.

No gun is immune to a kB!, and some guns actually are more prone to it (so I've heard), but... some things you can do to minimize your chance of having a critical failure are to use the recommended new factory ammunition in a clean well-functioning firearm that you are sure has an unobstructed barrel.

June 22, 2006, 12:12 AM
I usually drench the barrel with FP-10 and then clean it out with patches until the barrel seems dry enough. I used all kinds of solvents and paste to get the fouling out. Hopefully none of the chemicals mixed. And that H&k that got the reciever blown up, did all the ammunition blow up? Is that possible?

June 22, 2006, 04:15 AM
I watched a replica Yellow-boy go up once.

The owner loaned it to another shooter at a cowboy action meet. The ammunition used were the owners reloads.

Shooter fires one round at the target and three rounds in the magazine go off an instant after. Everybody but the Yellow-boy was OK, and the Yellow-boy was repairable.

The explanation was that the owner had used jacketed pointed bullets in his reloads. He had filed the points off but just not quite enough.

Many lever action center fire rifles use a tubular magazine, under the barrel. So, the rounds in the magazine look something like this: [=>[=> (the point of the bullet is against the center fire primer.)

The moral is to only use FP (Flat Point) bullets in a tubular magazine.

June 22, 2006, 12:19 PM
Not really a KA-BOOM in the literal sense of the word but once I wanted to try black powder loads in a 1st Generation .45 Colt. I weighed the 40 grains of black powder, this left just enough room to place a .454 round ball and be able to put a heavy crimp. When I pulled the trigger three chambers discharged at once, the load behind the barrell and the right and left below it. No real damage but left a splash of lead on the frame in front of the right chamber which I had no end of trouble getting off. I wonder how the original black powder cartridges avoided flashover. I don't think they used Cream of Wheat.

June 22, 2006, 02:00 PM
Wasn't/isn't black powder measured by volume, not weight?

June 22, 2006, 02:36 PM
Simple, bore obstructions cause KB's. End of story.

Wrong caliber ammo = bore obstruction.
Squib round = bore obstruction
Dirt/crap in barrel = bore obstruction
Hot reloads = bore obstruction (pressure builds too quicky, before round has a chance to exit the muzzle)

ETA: this is assuming you have a gun in good working order to begin with.

Jim March
June 22, 2006, 05:20 PM
I have never in my life seen (in person or in pics) a Ruger SA 44mag-size frame with the topstrap missing like that. Holy crap. That must have been a brutal over-charge...like somebody filled the case with a fast-burning powder or something, equalling a triple charge or close to it.


One rare cause of KBs:

If you take a gun in one caliber and shoot a LOT of a shorter caliber (for example, lots of 38Spl in a 357 gun) and then fire a real a 357 round without cleaning, you can get a KB. What happens is, a "crud ring" forms forward of where the 38 shell stops. When you push the longer 357 shell into that ring, it can prevent the shell from uncrimping on firing, raising pressures.

This is very rare, bordering on myth. There has to be a LOT of crud to a point where you have to shove the 357 shells all the way in, and the gun is on the weaker side. I'd be willing to bet that a tougher 357 gun such as the GP100, Blackhawk 357 on the 44-class frame or similar is pretty close to immune.

The cure is simple: after firing a lot of 38, clean it before firing 357.

The same goes for .44Spl/.44Mag, .32S&W/Long/Magnum families, etc.

June 22, 2006, 08:06 PM
Quote: Isn't black powder measured by volume, not weight?

Well, you can measure by volume which is getting the amount of BP in the case and still seat the bullet. But when the .45 Colt round was originated for the 1873 Single Action Army, that round was designated as having 40 grains of BP. I'm not sure of the granulation, I use FFFG. All factory loads used in previous years had (or were supposed to have) 40 grains.

Sheldon J
June 22, 2006, 08:26 PM
Well, you can measure by volume which is getting the amount of BP in the case and still seat the bullet. But when the .45 Colt round was originated for the 1873 Single Action Army, that round was designated as having 40 grains of BP. I'm not sure of the granulation, I use FFFG. All factory loads used in previous years had (or were supposed to have) 40 grains.
True that is why all of the old rounds were called such as your .45-40, there was the.45-70, .45-90 etc. and FFFFG burns faster than FFFG hence more pressure but I was always taught that in a modern gun with modern steel you would really have to work at it to blow up a gun with BP. Lastly I had always thought that the bullet setting of a round in a tube mag. was a myth, guess not after all. :what:

June 22, 2006, 08:36 PM
Here's another photo of the Marlin .45-70:


I'd hate to be holding that when it blew up.

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