What is that tarry stuff in some military rifle ammo case necks?

[NWPilgrim]

Got a question. Is there anything a handloader can use to replicate that tarry stuff some manufacturers uses to seal the bullet and case neck? Not only does it seems to protect against moisture but it really holds the bullet in place, that is hard to pull those suckers out.

I wouldn't be using it for range ammo but thinking about it for long term storage rounds. Any ideas?

[griz]

The stuff they use to seal the stub after they prune branches (pruning sealer? Not sure of the name) works well but is messy. Available in the gardening department at home centers. I'm not sure if that's what they use but it works.

[dahermit]

I wouldn't be using it for range ammo but thinking about it for long term storage rounds. Any ideas?

Sealants are not needed if you store your hand loaded ammo in inexpensive, surplus metal ammo boxes that you can find at any gun show. Ammo boxes have a rubber seal that keeps moisture out.
For a hand loader, applying sealant is much more trouble than it is worth.

[FlyFish]

I agree with dahermit, but if you really, really want to do it, Midway (and others, I'm sure) have a product specifically designed to do the job.

[PA-Joe]

Nail polish or super glue.

[Unclenick]

That Midway stuff is fine for primers, but their description of sealing a bullet with it is not what the U.S. military does with bullets. They apply pitch (also called bitumen or asphaltum or asphalt cement, being the tar-like binder in the black stone and asphaltum mix we apply to roads and driveways). They brush it on the inside of the case necks and let it harden before the case is sent to the loading machinery to be primed, charged and have the bullet seated. The seal is formed when the bullet pushes past it, as it is plastic enough to act a little like a thin layer of rubber, but is sticky enough to bond to the seated bullet. Their brass is always new, so there would be no carbon inside the case neck to prevent a good bond.

What I don't know is if they melt the pitch to apply it or if they use it in a solvent softened form, like the tree wound cement? The latter would be easier to apply, but more prone to dripping and melted pitch would be the fastest hardening.

On another forum, several of us discussed the value of cartridge sealing fairly recently. Some members turned out to have had unsealed rounds in boxes that were submerged during floods or that went through the laundry in a pocket by mistake, and generally no misfires resulted. One fellow even had shotgun shells that had twice been submerged for days at a time, and I think he said that added maybe 2% failures on each occasion. These were reloads, so the brass would not have been as smooth inside as it was when new.

So, it's hard to get water past either bullet or primer or shotgun wad fit. These are very thin cracks under contact pressure, and it pretty much depends on a scratch or other fault in one of the contact surfaces to create a leak path. Otherwise, you need water pressure significantly higher than the gas pressure inside the case to drive water in. So, if your ammo might be submerged to a significant depth, as, say, carrying ammo underwater during a dive might do, then the seals could pay off.

I've noticed foreign origin military surplus ammo I've pulled has no pitch seal. It did, however, have primer sealant. That makes some abstract sense to me, as the bullet bearing surface in tight contact with the case neck is usually longer than the tight-fitting portion of the primer in its pocket is. So, I can see water getting past the primer before it gets past the bullet in most loads.

[demigod]

Back when XM193 was first released for commercial sales by ATK (when you could get it for $85 per 500 rnds delivered ) , guys did home made tests on the rounds that didn't have case neck sealant.

One guy put a round in a 2 liter bottle of water over night, and pulled the bullet the next day. Powder at the case neck indeed did get wet and clumped together. But most of the powder charge was fine, and the round likely would have fired without issue.

The bottom line is this... if you plan on storing your ammo under water, seal the case necks and primers too. Otherwise, it's not necessary. And home case neck sealing jobs are ridiculously impractical and usually not as effective as a real military sealant job.

[jaguarxk120]

The sealer is ashphalt applied at the mfgr. It is a water proofing sealer used on military ammo.

[wncchester]

"The sealer is ashphalt applied at the mfgr. It is a water proofing sealer used on military ammo. "

Correct. And it's not needed on sporting ammo no matter how much it rains.

[griz]

A little clarification:

I had read somewhere about sealing ammo and thought I would try it. When I say the stuff "worked", I mean I loaded something like 20 rounds sealed and 20 with no sealant at all. I put all 40 of these rounds (223), plus 20 more 38 special with a lead bullet, in a bottle of water for a couple days. All the 223, sealed and unsealed, fired just fine, while a few of the 38s did not fire.

I was a little surprised that the seal of the lead bullets failed compared to the jacketed since I had assumed that the softer lead would conform to the brass better. There may also have been effects caused by the differences in diameter and condition of the brass. At any rate, I decided that sealing ammo wasn't worth the effort, and figured I would always distrust ammo that had been underwater anyway, so why bother. I also considered that the process of sealing might in itself present problems, and they wouldn't be as obvious as water logged rounds. Specifically, smearing some sort of goop in the neck and then seating the bullet could force some sealant on to the powder, which could possibly cause a misfire. As I already said, it didn't seem worth it. Now I just load 'em up and try to keep things dry.

[44 AMP]

Is the term they used to use describing the black sealant, back in WWII days. I don't know the exact formula. Probably still the same today as it was then.

[Unclenick]

I'm pretty sure they just use asphaltum and not asphaltum gum, which is a mixture of asphaltum and hydrophilic gum (water attracting gum) used in plate printing.

[NWPilgrim]

Thanks for all the info guys! I may play around with asphaltum out of curiosity as it sounds it is tedious to apply for any large number of rounds.

I was impressed that it defeated my Hornady collet bullet puller on some .30 Carbine rounds. Normally it takes little collet pressure to remove the bullets and leaves hardly a mark on the bullet. But with the sealed bullets I tried pulling several times with increasing collet pressure and heavily creased the bullets and they are still in the case. I finally got one sealed bullet out and saw what was holding it in the case.

I have an opened can of roof cement/sealant/patch. It is pretty thick and sticky, but maybe a thinned bit of this would do the same?

I would never have known case necks are sealed inside like this if I hadn't been doddle around the reloading bench and thinking, "What's inside these Carbine rounds anyway?" Occasionally I like to disassemble factory rounds to check bullet weights and see what and how much powder is inside (not that I would ever re-use the powder except in the same case and amount; normally I just dump it after weighing and "inspecting").

Anyone else ever find something new or interesting when disassembling factory ammo?

[Sport45]

I was impressed that it defeated my Hornady collet bullet puller on some .30 Carbine rounds. Normally it takes little collet pressure to remove the bullets and leaves hardly a mark on the bullet. But with the sealed bullets I tried pulling several times with increasing collet pressure and heavily creased the bullets and they are still in the case. I finally got one sealed bullet out and saw what was holding it in the case.

A little off-topic, but next time try seating them a little deeper first. That will break the sealant bond and make them much easier to pull.

[Unclenick]

NWPilgrim,

Ditto on using the seater die to set the bullet in a small fraction to break the seal, then use the collet. My Hornady Cam Lock has pulled many hundreds that way.

Even with the above, don't be surprised if you run into some that are stuck harder than others. The seal is down in the neck leaving the case in contact with the bullet higher up and "cold weld" bonding sometimes occurs their. The fresh ammo has pretty consistent pull, but on another board a former Aberdeen Proving Grounds employee said that in experiments pulling older ammo he would see anywhere from 60 to 600 lbs pull. That's one of the hazards of long term ammo storage.

I would not count on roofing cement to be a substitute for the pure asphaltum. A lot of the repair cement I've seen has some potent solvents and dry like a plastic cement. Try Dick Blick's art supply store. I believe they are on the web as well as brick and mortar. Look for Liquid Asphaltum. I still don't know this is how Lake City applies the stuff, as opposed to melting pitch chips, like we used to do to cast telescope mirror grinding laps, but if you let it dry long enough it should be OK.

[RWNielsen]

Made by permatex. It's a drying, asphault, based gasket sealer. It seems to me that it's pretty close to the stuff I've seen on pulled military rounds. I didn't know the trick on seating them deeper and played hell getting one apart.

[demigod]

I wouldn't be running mystery sealants in my case necks. Keep in mind that a certain amount of that sealant gets stuck on the bullet jacket and thus fired down your barrel. I don't know if it cooks off or what, but I'm sure the military took that into account. I doubt if Chuy's roof goop was thinking of case necks for their product.

[Vandelescrow]

Just curious,

Wouldn't you have to adjust how much powder your using? If they are so hard to remove the projectile, would this not increase internal pressure when fired?

I'm storing my ammo in an army surplus metal ammo can lined with a plastic bag and a packet of cilica in the bag.

[demigod]

Wouldn't you have to adjust how much powder your using? If they are so hard to remove the projectile, would this not increase internal pressure when fired?

I've never seen a shred of evidence to suggest that. I mean... people fire really old Mil ammo all the time with no adverse pressure signs.

40 to 50 thousand chamber psi in a .223 remington for example can probably break a bullet seal with no problem.

[Unclenick]

Demigod is correct. This is an issue of scale. Chamber dynamics are such that the bullet doesn't start to move until several thousand psi are already behind it. The neck actually expands away from the bullet starting at the shoulder end and moving forward. That's why the mouth is often left curled slightly inward. It was the last to expand and gas bleeds past it as it gets close to open and equalizes the pressure before it stretches far enough to remain expanded.

[NWPilgrim]

Thanks guys for the reminder about breaking the seal by seating deeper before pulling. I've read that before but forgot it over the years. That is a right handy technique to keep ing mind the next time!

[brickeyee]

Thanks guys for the reminder about breaking the seal by seating deeper before pulling. I've read that before but forgot it over the years. That is a right handy technique to keep ing mind the next time!

It works on old loaded rounds that may have become partly 'cold welded' between the bullet and brass case also.