Underwater Boomsticks… Go BOOM! In a Bad Way!

FullMag, known for their eccentricities with .50 BMG, miniguns, and det cord is at it again, this timed armed with Modern Sporting Rifles and… a pool? Yep, Modern Sporting Rifles go swimming including the AK-47 and the AR-15.

Per usual filming, the video is complete with gratuitous slow-motion, of which the centerfire rifles are utterly mesmerizing. The energy of the round exiting the barrel causes massive cavitation in the water (cavitation is the phenomenon when something moving through water releases the air that is within the water).

Surprisingly, the AR-15 does not blow up on the first round shot… but does blow up on the second shot, having complete pressure containment failure. Bolt components are blown out the magazine well along with the follower being broken into pieces while the magazine is forcefully ejected from the gun.

On a personal note I do believe “to each their own” but the scenario presented was sheer idiocy, especially with the hands around the barrel at a known failure point. Normally, the barrel will blow, which at 50,000+ PSI is likely to take ones fingers off, even with the water helping mitigate the blast.

So, dear readers, enjoy the video and learn from the mistakes of others – don’t fire your AR-15 underwater (but do have fun with AK’s and Glocks).

Nathan S

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

The above post is my opinion and does not reflect the views of any company or organization.


  • Martin Grønsdal

    Why? Why not.

    • Roy G Bunting

      High chance of injury and bad press for the community? For me the first reason is enough.

      Also, wrecked firearm, I’m not a big fan of doing thing I can reasonably foresee as breaking expensive things or hurting myself.

  • Bob

    “This timed”?

    Anyway, that was predictable. AR not likey water.

  • MPWS

    Case of intelligence and idiocy in a weird combination. Does Obamacare cover for negligent injury/ dismemberment?

    • PK

      It depends on the individual policy, but generally medical insurance covers negligent injuries and accidents, yes, regardless of who caused them or how. Later settlements between companies may move the blame/payment to, say, a car insurer or similar, but the main point is that in essence even stupidity is covered. After a deductible, anyway!

      • MPWS

        That sounds generous, in a good American fashion. I am sure layers will get their cut.

        • I don’t think it’s limited to Americans and their superior moral standing.

          • Sgt. Stedenko

            It must suck to be so bitter and inferior.

          • Yup, it’s not easy.

  • Anonymoose

    VSO did a series a few years ago where they shot a Glock, SIG, 1911, and maybe an XD underwater. All worked okay, iirc.

    • AndyHasky

      Talk about a stupid video…

  • Austin

    Didn’t Smarter Every Day do this a few years ago with help from The So Mo Guys

  • stephen

    One of these days someone will do something (stupid) that will hurt or kill someone, then the liberals will whine on how bad guns are.

    Oh yea we have already seen this numerous times; do we really need to push the envelope and do more senseless videos?

    No thanks.

  • john huscio

    Shades of cokeman2423

  • UnrepentantLib

    Guys got way too much free time on their hands.

    • He says right here in this video that he has other jobs in the industry, which gives him access to range time and presumably some tech (even if his channel was not already successful).

  • lowell houser

    I got shouted down once for saying that it’s not the bore diameter that blew up the AR15 when it’s full of water, but that it’s the water in the gastube flashing into steam and over-pressuring the receiver. So could somebody shoot a 5.45 AK underwater and settle the question?

    • Joshua

      Except the Army has done a whole lot of water tests to show that it is indeed obturation of water in the bore.

      However this is when you are discussing OTB tests in whish external pressures are different.

  • IndyToddrick

    First round must’ve sucked water into the gas tube, then the tube had (excessive) hydraulic pressure?

    • Joshua

      Yes. The bolt cycling causes water to be forced into the tube.

  • pithy

    God, I hate stupid generic dramatic music. Hate it.

  • AFAIK, cavitation is temporary low-pressure (vacuum) cavities formed in the low-pressure areas because water is almost incapable if “stretching”. So there isn’t air in them, which makes them so dangerous – cavitation bubbles collapse forcefully, with water creating a water hammer effect, heat and even light sometimes.

    This secondary “clap”, if strong enough, itself acts like an explosion and creates another bubble in its stead (although I’m not sure what this bubble is like, is it air this time or smaller vacuum again).

    EDIT: I’m not saying what we see in this video is purely (or even partly) cavitation; that’s my point. Although the “see-saw” of pressure and intertia with oscillating bubbles certainly is there.

  • AK™

    Andrew Tuohy did it better.

  • Should have been done remotely using a jig.
    He’s lucky he still has his fingers and hands.