What’s Primer Sealant? And Why is it On Some of My Commercial Ammunition?

nato primer sealant winchester ammunition

courtesy TTAG reader

A reader asks . . .

I picked up two boxes of Winchester 9mm bulk at my local Wally World and found five of these red primers.

Any ideas?

That red stuff you’re seeing on the back of those round is primer sealant.

When primers are press-fit into cases during the manufacturing process they usually form a tight enough seal for civilian use, keeping out most of the moisture and protecting the powder and primer components from corroding. But if you’re out in the elements (say, crossing rivers or caught in a monsoon) some moisture can leak into the cartridge and ruin the powder (and subsequently your day).

That’s where primer sealant comes in. Primer sealant is typically a lacquer-like compound that is applied over the primer to form a watertight seal and make the cartridge almost completely impervious to the elements.

It’s an extra step in the manufacturing process though, so for ammo destined for civilian sales they typically don’t bother. Military customers, on the other hand, like primer sealant on their ammunition. That symbol on the bottom of both rounds is a NATO headstamp, meaning the rounds were made to their specifications.

If you’ll be going on a hunt and want to ensure that your ammo supply stays dry, you can buy primer sealant and apply it yourself to your ammunition.

So how did those rounds with sealed primers get into your bulk ammo pack? Well, it probably has to do with our decreasing involvement in the middle east.

When the Iraq and Afghanistan wars were heating up, the military started placing orders for massive quantities of ammunition. In response the major manufacturers ramped up production to meet the demand and made those components according to the military specification (sealed primers, etc).

With the gradual draw-down of U.S. forces, what we’re seeing is that some ammo manufacturers produced more military spec components than were needed. So some of the ammo they were expecting to sell to our boys in camo were just sitting around the warehouse collecting dust. Instead of sitting on it, they’ve fed some of this inventory into civilian distribution channels.

You got a few primed cases in your bulk pack that were destined for the military and were re-purposed for civilian sales, packed with the rest of the lot and sent out to your local Wally World.

 

comments

  1. avatar cmac890 says:

    If there’s one thing public elementary school taught me, it was to never EVER ford the f*cking river.

    1. avatar Tim says:

      Careful, don’t die of dysentery!

      (Love playing Oregon Trail with the boy, and having him holler out, “Mommy, you just died of dysentery!”)

    2. avatar WARFAB says:

      Only people of a certain age will have any idea what you’re talking about. Those who survived those harrowing journeys all share a common bond.

      1. avatar arc says:

        The game was too slow for me to ever be interested in it… family liked it though.

        I much preferred ZZT, Jill of the Jungle, and Duke Nukem

        1. avatar tmm says:

          “Damn, those alien bastards are going to pay for shootin’ up my ride…”

        2. avatar jakee308 says:

          “I’m here to chew bubble gum and kick ass and I’m all out of bubble gum”

    3. avatar Cambo says:

      ROFL. I have that game on my phone. My my has tec come along way

    4. avatar Draven says:

      y’all should check out ‘Organ Trail’ on Steam… its a ‘zombie apocalypse’ pastiche of it…

    5. avatar Agreed says:

      The one thing I learned was the life of a future grandfather clock merchant is never easy. Food and ammo and for quitters

    6. avatar Chris. says:

      You just had to look at how deep the river was. Chest high on an adult human 3-4 foot which is nose high on the Oxen. so they drown. If the water was less than 3 feet it worked great.

  2. avatar Geoff "I'm getting too old for this shit" PR says:

    I’ve had ammo that had the red ‘sealant’, and it flaked right off when a fingernail touched it…

    1. avatar Sandy Reed says:

      The ‘seal’ is actually between the edge of the primer and the sides of the primer pocket, the red on the cartridge base is just slop from the process

  3. avatar ROBERT Powell says:

    i always sealed my primers although it was for a different reason. i used different colors for different load-weights of powder. white for light loads blue for standard, green for target, red for hot-long range, black for match..

    1. avatar Geoff "I'm getting too old for this shit" PR says:

      Yeah, the nail polish was for your ammo.

      Suuuuuuure…. 😉

      1. avatar Chris. says:

        I wear nail polish on my fingersnails. Never tried it on my primers. They don’t need to look pretty.

    2. avatar WI Patriot says:

      I do the same, but use sharpie markers, as they will polish off the next go ’round…

  4. avatar possum says:

    I use finger nail polish. Now that I think about it maybe try lipstick to seal the chamber’s on the 51 Navy. Embrace the rainbow, go whole hogg.

    1. avatar WI Patriot says:

      As do I, it’s a great alternative…

  5. avatar Vlad Tepes says:

    Do not trust factory primer sealers as they don’t always work. As a matter of fact things like gun oil and W.D. 40 are usually not stopped by factor primer sealer because many times its actually that worthless. My hunting loads and woods self defense loads to stop cougars, etc are hand loads. I use a drop of polyurethane on all of my defense ammo primers after they are seated. I even smear a bit at the junction of the case neck and the bullet. You can buy real bullet sealant when loading but its a real pain and mess to use.

    I once dumped some loaded rounds treated with polyurethane in a can of oil for a couple of days and they all fired off with no problems. I did this after an incident when some of my factory ammo failed to go off because it got oil soaked even with factory sealant so after than I started to oil proof my own ammo even brand new factory ammo and especially my carry ammo when venturing out into the asphalt jungle.

    1. avatar Tim says:

      That’s interesting! I had read of an experiment on “Box O’ Truth” that came to the opposite conclusion:

      https://www.theboxotruth.com/the-box-o-truth-39-oil-vs-primers/

      It might be interesting to see how your conditions were different than his.

      1. avatar Vlad Tepes says:

        I still have a Browning FN Barrel in .25 acp that is bulged because the cartridges got oil soaked. The first shot went pop and I actually saw the bullet fly slowly down range and fall short of the target as it hit way low. The next shot did not go off because the primer failed to ignite so I ejected the round and jacked in another round and it went only pop and I did not realize the bullet had stuck mid way down the barrel. The next shot of course bulged the barrel. I had the primer fail on one of the rounds but on the other three rounds I had oil soaked powder. So in conclusion a poorly sealed primer coupled with a bullet not sealed properly will let oil into the power. AGAIN ALL THIS HAPPENED WITH FACTORY OIL PROOFED ROUNDS WHICH ALL FAILED.

  6. avatar WI Patriot says:

    I use it, hunting/shooting is NOT confined to bright sunny days…also helps preserve during periods of storage…

  7. avatar daveinwyo says:

    Back in the days of my youte I scuba dived in shark waters. Used a .44mag bang stick. We would drop the rounds in clear nail polish. Seemed to work. Never had a misfire. But then I only needed the stick about 4 times. Best was that I could still use them in my Ruger Super Blackhawk. Have had ammo straight from the ammo dump bunker fail to fire from humidity in Panama. Jungle is rough on guns and ammo.

    1. avatar Baloney says:

      You ever seen videos of guns firing underwater? Practically useless for defense

      1. avatar Dave says:

        A bang stick under water is a contact weapon, that is you have to strike the target to fire.

      2. avatar GridSquare says:

        “Baloney” sure doesn’t know what a bang stick is.

      3. avatar Matthew says:

        Hey Baloney, this guy tells you of his first-hand personal experience using a tool and your response is to say that a video you saw says that it wouldn’t work? Sigh.

  8. avatar Minuteman says:

    That’s some really crappy looking brass to be new ammo. Something smells.

    1. avatar Geoff "I'm getting too old for this shit" PR says:

      Did you bother to read the article?

      The article explains *why* you may find some primer-sealed rounds in bulk-pack ammunition…

  9. avatar HK says:

    Military ammunition is sealed at the case neck and primer to waterproof it. Usually, it has an asphaltic sealer on the neck applied before loading and then solvent is used to reflow the asphalt to seal. This results in @5% leaking cases at 1/2 ATM under water, but it’s so much better to use external ammunition sealant which was submerged 320 feet then fired 100%. There is a sealant you can buy called Accurizer…UV cured with a high power flashlight…it uniforms the bullet pull above the mechanical tension of the neck to the metal and “snaps” predictably. In one case it gave 7,62 NATO ball 140fps for free, just by raising the shot start pressure to better burn all the powder…and at the same time visible muzzle flash disappeared.

    And there you go with your answer…happy now?

  10. avatar Holdfast says:

    It is highly unlikely this is true:

    “With the gradual draw-down of U.S. forces, what we’re seeing is that some ammo manufacturers produced more military spec components than were needed. So some of the ammo they were expecting to sell to our boys in camo were just sitting around the warehouse collecting dust. Instead of sitting on it, they’ve fed some of this inventory into civilian distribution channels”

    The US military has its own ammunition factories which crank out gazillions of rounds. If the round is made for the US Government, than it has been paid for by the US Government and it is owned by the US Government. The Feds have been wildly against selling surplus ammo for current weapons systems for at least 30 years.

    Primer sealant was probably applied because the rounds purchased were part of a NATO spec commercial lot with primer and a NATO spec commercial lot without primer and there was some mixing and matching of lots.

    Sellor & Bellot put primer sealant on all of their rounds.

  11. avatar HK says:

    OK, thanks for the defense down there but there’s little need since I am correct and our colleague has not tested it. That’s because (s)he would have liked it if (s)he did.

    So here we go with one more good trick for the UV cured external ammunition sealant…it not only resists diving deeper than you can go down to get it if you dropped your mag (320 feet) and still goes bang…but now hear this:

    While testing the stuff to present to the government, I forgot a bag of UV sealed 5.56mm that was full of liquid WD-40 penetrating lubricant for about five months. I thought by then there was no way they could work, then they all fired at full velocity. So by all means lube the hell out of your gun with any ordinary oil if you want to and don’t forget the mags…if there is a thin blue ring around the primer and case mouth.

    Advice is if you are using your ammo for anything really serious, like a “Fishing Pistol” for fly casting backcountry Alaska or fighting terrorists: seal your ammunition at both the primer and case mouth better than the military does with that Asphalt stuff! It costs a just couple pennies a case and you’ll prove to everyone how smart you are instead of how dumb you were.

    And there you go again with an even better answer…seal your ammo.

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