Some thought: Doesn't this mean AR cannot fire in the rain?

[ShootAndHunt]

Read my AR manual and find the following comment:

You cannot fire if there is water inside the barrel, or it will explode!

I find the similar statements in the army's M16 manual.

This made me think: Doesn't this mean AR cannot fire in the rain?

When firing in the rain, especially when it is heavy, it is impossible to prevent water from into action, magazine, and finally the barrel. If the above statement holds, this means you cannot safely fire an AR rifle in the rain. This may mean nothing to usual civilian shooters, but for soliders, this might mean disaster! You cannot always choose time, place and weather to fight!

According to this statement, it seems with an AR, soldiers are back to the 17 ~ 18th century of the black powder period, when in a rain they couldn't fire because the prime are wet, but this time you get something more serious, you can fire but the rifle will explode!

Of course I believe this is not true since soldiers are fighting in any weather condition with their AR, then, how to explain this?

Another question: Why AR may explode when there is water in the barrel? I never heard similar things about AK47, the latter is even supposed to be able to fire when picking it up from the mud or water! I also saw demonstration videos that special forces emerge from the water and fire their MP5 immediately, and the MP5 is regarded as a more delicate weapon.

 

[Marnoot]

I couldn't say specifically for the AR-15. I'm assuming it means if the barrel is filled with water. For instance, if you tried to fire it under water, the water in the barrel would cause a dramatic increase in pressure, quite possibly beyond the maximum of the chamber/mechanism, causing a KB. That's just a guess though, or maybe it's that it would be at regular pressure but for much longer, causing metal stress?

 

[FPrice]

"You cannot fire if there is water inside the barrel, or it will explode!"

I think that refers to submerging the firearm and the barrel being COMPLETELY filled with water. Now I personally don't know if this is actual fact, just a possibility, or a myth. There were certainly many firefights in VN in the rain and I have not heard of mass blow-ups there.

 

[4v50 Gary]

Bore obstructions including water can damage the firearm (bulge the barrel).

 

[Tamara]

To expand on Gary's post, bore obstructions (including water) can damage any firearm, including bulging or splitting of the barrel, or sending bits of the bolt flying rearward at high rates of speed.

 

[Correia]

This is why you keep your muzzle pointed down instead of up when you are using it in the rain. Moisture can and will get in your barrel. A blockage can cause a blown barrel. This is easier to do in a .22 bore instead of a .30 bore, just because it takes less to effectively block it.

I use guns in the rain all of the time. The key is to just keep your muzzle pointed downwards. The pull it out of the mud and shoot test that you refer to, believe me, they shake the barrel out first. Any gun will blow with a plugged barrel.

 

[Grump]

Reports I read indicated that the troops in jungle warfare needed to be more aggressive in getting water out of M16 barrels after water crossings than with .30 caliber weapons.

It's a little capillary attraction problem where the larger bore pretty much drains by itself, but the .224 bore is a noticeably harder to clear out. Firsthand accounts I'm familiar with say a single drop in the barrel will NOT take the gun out of the fight.

In a similar vein, an Army report I read about an incident a few years ago (NTC in CA?) indicated that poking the muzzle in a sand dune as you dive for cover, with the muzzle staying up, can get enough sand in the bore to cause a rather spectacular barrel/receiver failure with the next shot. The troop *was* injured, IIRC.

 

[Vern Humphrey]

In Viet Nam, in the early days of M16 use, there were many occasions of people getting the barrel filled with water -- for example, falling in a rice paddy -- and attempting to fire.

The problem is that the .22 caliber bore is so small that once water is in the bore, surface tension will hold it there. Troops were taught to "crack" the action -- pull the charging handle back a bit, to allow air to enter from the breech so the water could drain, then using the bolt assist to make sure the round re-chambered and the bolt locked.

We also used condoms as muzzle protectors -- later the Army issued a plastic muzzle cover.

In a similar situation -- even heavy rain, it is best to have a muzzle cover, and to occasionally "crack" the action, just to be sure.

 

[Redlg155]

For instance, if you tried to fire it under water, the water in the barrel would cause a dramatic increase in pressure, quite possibly beyond the maximum of the chamber/mechanism, causing a KB.

I don't that is quite true since there are some scuba divers that carry Glocks for anti shark use underwater. Although I don't claim to be a physics major, I believe the pressure in the barrel and outside of the barrel would be equalized underwater, so it wouldn't be that much different than firing in air, except for the greater density of water slowing the bullet down and possibly retarding the action, thus keeping if from cycling correctly. Again, I'm no physics major, so someone correct me if I'm wrong!

However, in keeping in context with this discussion, you would have serious trouble firing a weapon with the barrel filled with water that was not completely submerged.

Good Shooting
Red

 

[ShootAndHunt]

So this problem seems to be related to the small caliber, not to a specific rifle, in this case the AR? It makes sense since I never heard that M1 or M14 has this problem, but they also differ in design.

Does anybody know whether the same problem happens on the AK74, whose caliber is 5.45mm, even smaller than the AR's 5.56mm?

It now seems to me that when in the rain, you could still use your rifle, but have to use your AR more carefully, something not so good for the soldiers under great pressures in the fighting.

 

[Vern Humphrey]

The 5.45 has the same problems -- but this weapon has rarely been used in areas with lots of rice paddies and monsoon rains. It isn't, therefore as apparent.

A muzzle cover goes a long way toward solving the problem.

In fact, I routinely use a muzzle cover when hunting in snow or similar conditions -- even with my .35 Brown-Whelen. You only have to fall once, find the muzzle plugged with snow, and realize you have no cleaning rod with you.

 

[BrokenPaw]

I don't that is quite true since there are some scuba divers that carry Glocks for anti shark use underwater.

How would you be able to tell whether the Glock-under-water KB was because of the water, and not just because it was a Glock?

Oh, you know someone was going to say it...

-BP

 

[Henry Bowman]

bore obstructions (including water) can damage any firearm, including bulging or splitting of the barrel, or sending bits of the bolt flying rearward at high rates of speed.

Just so we're all clear: that's a BAD thing, right?

 

[MagKnightX]

Yes, it is a VERY bad thing.

I think that one of the shoot-through muzzle-covers ought to relieve much of the problem, however.

 

[Obiwan]

I have shot mine in the rain.....

As well as some pretty large hail

No problems so far

 

[hksw]

I've always wondered about a similar situation when I see those scenes and commercials showing spec op guys emerging from the water in a river or on a beach with M-16/M-4s. Most of the shots I've seen they never shoot right after surfacing and more than likely is just done that way to make the scene more 'hardcore' but it makes me think what do they really do when they come out.

 

[benEzra]

I don't that is quite true since there are some scuba divers that carry Glocks for anti shark use underwater. Although I don't claim to be a physics major, I believe the pressure in the barrel and outside of the barrel would be equalized underwater, so it wouldn't be that much different than firing in air, except for the greater density of water slowing the bullet down and possibly retarding the action, thus keeping if from cycling correctly. Again, I'm no physics major, so someone correct me if I'm wrong!

The density of the water in the barrel is the big problem. When a gun is fired, the powder does not detonate instantly, but deflagrates pretty much the whole time the bullet is in the barrel (ideally), thereby smoothly accelerating the bullet while keeping chamber pressures down to a safe level (typically 40,000 to 45,000 psi). However, this is dependent on the bullet being FREE TO MOVE down the barrel. If the barrel is filled with water (which may amount to many times the mass of the bullet), the bullet will accelerate much slower than usual, and chamber pressures will rise astronomically, usually until the steel surrounding the chamber fails in tension and vents the pressure to the atmosphere.

The reason a Glock 9mm can be fired with a barrel completely full of water is that (1) the 9mm has a LOT less powder behind it than a .223, (2) it operates with a LOT shorter barrel, meaning that the water column ahead of the bullet has a lot less mass per unit of bore area. (A typical Glock barrel is ~4 inches, while a typical .223 barrel is 16 to 20 inches.) BTW, a .40 caliber Glock will kB if fired underwater (there was a thread on GlockTalk a long time ago about a guy who tried this, IIRC, and severely injured his hand).

Another problem can happen if the bullet accelerates down the barrel and then slams into an obstruction halfway down. This isn't as likely to cause a chamber failure, but WILL bulge the barrel since the local pressures at the impact site are immense.

 

[El Tejon]

Just finished class in the pouring rain with an AR. No explosion for any of the 24 of us.

ShootandHunt, who do you think wrote that advisory? I give you a hint: they are EEEVIL.

 

[Turk]

I've never tried to shoot an M-16 or AR underwater but trust me the barrel doesn't explode if fired in a monsoon down pour.

Turk
173rd ABN Bdge (Sep)
RVN 68-69

 

[ShootAndHunt]

who do you think wrote that advisory? I give you a hint: they are EEEVIL

This statement could be found in almost any of the AR manuals, including the Army's.

 

[shoobe01]

The Naval Safety Center website here has an article about just such a thing:

Some of the coolest posters in a recruiting office show Sailors and Marines emerging from the water with their rifles pointed toward the camera. You don't see what could happen next, when one of them fire one of them fires his weapon and it disintegrates in his hands, and he has to transition to a pistol. Recently, two M4 carbines were destroyed in this manner when Sailors shouldered their carbines and fired as they came out of the water. In 1996, a similar mishap occurred, damaging five carbines...

This repeats the info I have read before where you are supposed to open the chamber to let the water drain as the manual says, BUT adds info about how /long/ you have to do this. Also note that although I had always heard supressors need to drain longer, they don't seem to (makes sense -- many are liquid filled on purpose)

Testing following a similar mishap in 1996 determined that 10 to 12 seconds are required if the weapon is in condition one and 4 to 5 seconds if in condition three. The main difference between the two cases is that suppressors were not used in the 1996 mishap, but they were used during the recent case. This raised the question of whether additional procedures are necessary. Comparison tests show that an M4 with suppressor drains at the same rate as one without--no additional procedures are necessary.

 

[pignock]

An RVN campaigner I used to know told me his unit (I don't remember whichone it was) carried electrician's tape on patrol and used short pieces to cover the muzzle. When it was time to shoot, they shot through the tape without ill effect.

Can anyone verify this?


Thanks,

Keith

 

[BeLikeTrey]

I don't know about that particular...

But i do it currently with my rifles. I have seen my hunting buddy imbed his muzzle in the dirt unaware. I had to let him know before he had an accident. Since then, both of us use tape. I use a bit of duct tape-just enough to cover the opening.

 

[El Tejon]

Forgot to add: only way rain is danger to AR is if it washes away lube.

Had a FAL in class that boogered up because of rain. Guy globbed on more lube and it ran just fine.

 

[JNewell]

If it ain't raining, we ain't training...

I have spent plenty of time, too much probably , standing around and shooting ARs in the rain and have never seen one bulge or blow a barrel. Keep the muzzle down, "African carry" style.

I have also seen guys slip and dig up a clod of sod with the flashhider. I have never seen an accident due to failure to clear the obstruction, but I have heard reports of it happening when the obstruction wasn't cleared. In one case, the barrel blew near the receiver and took parts of several fingers.