Out of curiosity what could I do to my AR that would make it more reliable after a complete submerge underwater? I’ve seen that there were Maritime floorplates for pmags and my LWRCI has cuts in the bolt that allow water to come out of the buffer tube and they also have buffer tubes on their site that actually have holes in the positions of the buffer tube. Call me crazy but I’ve been bored and getting a little insomnia. This would be for a regular AR not a Piston one.
After being submerged and bringing AR back out of the water, point muzzle down, do a press check to break seal on bolt (allow barrel to drain), chamber round and shoot if needed. However, it is always best to clean weapon and lube when time premits.
CD
CD, thanks for the reply and the great pics (especially the ones in the Scuba Diver thread). Would you say a lot of water gets in the buffer tube area?
Yup. It is one of the leading reasons that DI guns don’t do well if they aren’t drained (other than barrel obstruction).
Breaking the bolt out of battery and dropping the muzzle does a few things- it breaks the seal in the chamber, allowing water to quickly drain out of the barrel, it breaks the seal of the gas key and gas tube, allowing water to drain out of the tube quickly. The receiver extension drains pretty fast without any aid.
You can also drill a hole in the magazine floor-plates to let them drain faster, since water in the magazine can cause issues when firing. The hole needs to be small enough to not let too much crap into the mag when proned out, but big enough to actually let water flow out.
Is anyone else amused at the cute little cupidfish logo on that photo.
On a long track providing cover for K9 through a very rural area, my rifle and I took a spill into a playa lake after a huge rain storm. I turned the weapon muzzle down and water began to run out. I did the above technique and I was suprised as to how much more water came out of the rifle after press-checking.
Just for S&G’s, after the track I took the rifle out to the range and ran a full mags through it without issue but it was filthy. My T1 was also just fine. 
Any idea where the rest of the water came from, after the press check?
I’m gonna go out on a limb jhere and say that it came from inside the weapon. 
The water will drain, eventually, without press-checking, so think of volume spaces: some in the barrel, some in the magazine, lots in the receiver extension and upper. Hold the gun down, water will start to drain from whatever area is closest to the ground first; simple gravity.
Crack the bolt a bit, and it’s like you just punched a hole in the base of the can of beer you’re preparing to shotgun. Air rushes in, water follows the path of least resistance. It may appear as if you opened a floodgate, when in fact you just introduced an easier means to let air get back in and replace water.
That’s some funny shit! Cracking the bolt does make sense now. Thanks for the response.
Some funny here may help prevent un-funny for somebody later down the road, hopefully. It’s less a reliability issue than a safety one, since water doesn’t compress. While I personally would not do so, it’s possible to shoot out some dirt out of a muzzle; water…not only no, but f**k no.
There was a fatality not too many years ago, Co E/4th Recon Bn in Alaska, if I recall correctly, because a Marine took a shot after coming out of the water, having forgotten to crack his bolt.
I saw one of our kids forget the same thing at Lejeune;small-craft unit, a water extraction on Stone Bay, couldn’t get close enough to shore so our crunchies had to wade/swim out to us. We were firing blanks, so the BFA must’ve kept too much water from infiltrating the system. Popped his magazine out and scared the dogshit out of everybody on my boat, but no injuries.