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31BMSG

Ammo can seals

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When I clean up an ammo can for a cache container I always remove the seal to clean it and check for rust underneath. Earlier today I was working on a few and wondered about the availability of replacement seals for 5.56 and 50cal cans. So far my search has come up empty but if anyone knows of a vendor that sells such a thing I would be appreciate it if you could pass that information along. It's been 7-8 years since I purchased and replaced seals on several 30cal cans but I can't even find those now.

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These have been a real bugger to find for years. 

 

McMaster makes some good strips (see https://www.mcmaster.com/rubber-strips  and scroll down to the strips and pick either a 30 Shore A or perhaps 40 Shore A durometer material).  This softer 30A/40A stuff compresses more and so deals with any irregularities in the mating surfaces without making it a right bugger to get the lid closed. 

 

Since it's strip, you'll be on your own to deal with the seams -- a bit of silicone seal usually gets it done, even when you don't quite get them cut perfectly.

 

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20 minutes ago, ecanderson said:

These have been a real bugger to find for years. 

 

McMaster makes some good strips (see https://www.mcmaster.com/rubber-strips  and scroll down to the strips and pick either a 30 Shore A or perhaps 40 Shore A durometer material).  This softer 30A/40A stuff compresses more and so deals with any irregularities in the mating surfaces without making it a right bugger to get the lid closed. 

 

Since it's strip, you'll be on your own to deal with the seams -- a bit of silicone seal usually gets it done, even when you don't quite get them cut perfectly.

 

Thanks, especially for the specs, I'm very familiar with McMaster-Carr but don't have a clue about rubber specifications. What I have is in good shape but since the seal is out I'll make a template for future use in the likely event I have to make my own with what you provided.

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I've heard that bathroom caulk acts as a reasonable replacement, but I haven't tried it personally.

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To get a good watertight seal, it takes some real technique to run a perfect bead of RTV along that kind of distance and then flatten it out to a very uniform depth.  It's not like caulking around a tub where slight variations in height really don't matter. 

 

This kind of thing is much easier to do when, instead, you're gluing two surfaces together (as in certain types of window replacement where the glass is RTVd into the frame) and you can 'squish' everything out to a uniform depth.  It really won't do to try duplicate that 'squish' trick by trying isolate the RTV from the lid with wax paper or something, since seal really needs to be compressed during closure, and this would cause the lid to bury itself into the RTV as the RTV sets instead.

 

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41 minutes ago, ecanderson said:

To get a good watertight seal, it takes some real technique to run a perfect bead of RTV along that kind of distance and then flatten it out to a very uniform depth.  It's not like caulking around a tub where slight variations in height really don't matter. 

 

This kind of thing is much easier to do when, instead, you're gluing two surfaces together (as in certain types of window replacement where the glass is RTVd into the frame) and you can 'squish' everything out to a uniform depth.  It really won't do to try duplicate that 'squish' trick by trying isolate the RTV from the lid with wax paper or something, since seal really needs to be compressed during closure, and this would cause the lid to bury itself into the RTV as the RTV sets instead.

 

 

I'm thinking a rubber strip would be better, as previously mentioned, if the metal channel (the part that "crimps' the gasket) isn't too rusted.  Even then, gluing sections of carefully cut high-quality flat rubber strip might work, using RTV or gasket sealer.  The corners of the new gasket could be sealed with RTV.

 

By the time my ammo boxes seals fail, I'm planning to replace the whole box.  I start with a box that looks almost factory-fresh and seals well, maybe that helps with the endurance.

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38 minutes ago, kunarion said:

By the time my ammo boxes seals fail, I'm planning to replace the whole box.  I start with a box that looks almost factory-fresh and seals well, maybe that helps with the endurance.

That was my original intent but my supply of no-cost ammo cans is running low and I'm not keen on paying crazy prices for used ammo cans. I made a cardboard template of the seal I have on my work bench and will shop around for sheet rubber with the specs ecanderson gave. I would rather have a one piece seal but the cost of a sheet of rubber may prohibit that notion.

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Posted (edited)
13 minutes ago, 31BMSG said:

That was my original intent but my supply of no-cost ammo cans is running low and I'm not keen on paying crazy prices for used ammo cans. I made a cardboard template of the seal I have on my work bench and will shop around for sheet rubber with the specs ecanderson gave. I would rather have a one piece seal but the cost of a sheet of rubber may prohibit that notion.

 

Can you get scrap ammo cans?  All you need is the can lid with an intact seal.  Pry the crimp apart on both, use the "new seal".  Even better, the ammo can might be rusted out or very beat up, with a decent enough lid where you can transfer the entire lid.

 

Next time I visit an Army surplus store, I'll ask if they have a source for super messed-up ammo cans that I can have for free.  I haven't tested if the "rubber gasket" universally fits in every lid.  My oldest cache has been in place flat in the dirt and mud for 11 years, and the metal is not rusty and the rubber seal is great.  None of my other ammo can hides have any issues with seals.

 

Edited by kunarion

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Did you ask the folks here  for a name of a supplier ?   They might make their own gaskets, but every one has to conform to mil. specs, same with these guys.

I'm guessing you might have already gone through the list to ask around as well.  

Similar to kunarion,  these folks might be worth a shot for "where can I get..." info, or have a couple of "extra" can tops.

 - All would be worth a cordial email I'd guess.  Can't hurt.   :)

We never had an issue with rust under the gasket,  but might spray (after covering the gasket with frog tape) a little rustoleum if it looks like the coating's going.

"Cleaning" was usually just a wet sponge, dried, and a light wipe of silicone grease with a rag.  

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31 minutes ago, cerberus1 said:

Did you ask the folks here  for a name of a supplier ?   They might make their own gaskets, but every one has to conform to mil. specs, same with these guys.

I'm guessing you might have already gone through the list to ask around as well.  

Similar to kunarion,  these folks might be worth a shot for "where can I get..." info, or have a couple of "extra" can tops.

 - All would be worth a cordial email I'd guess.  Can't hurt.   :)

We never had an issue with rust under the gasket,  but might spray (after covering the gasket with frog tape) a little rustoleum if it looks like the coating's going.

"Cleaning" was usually just a wet sponge, dried, and a light wipe of silicone grease with a rag.  

Perfect, exactly what I was looking for. Cordial as I can get email on the way to "these guys", thanks! :)

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I'd never thought about replacement seals, the cans tend to either rust out (we get a lot of rain and humidity here) or be nicked before the seals go. The comment about the Shore Hardness rating is the key one I think.

 

Theoretically, it shouldn't be too hard to 3D print a mold and then pour seals using one of the appropriate epoxy rubbers. In practice, it may be a lot harder than I think...

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15 hours ago, beerslayer2000 said:

I wonder if household weather stripping would work... either the rubber kind or the foam kind.

I think you find the design of the original seals make that quite difficult.  They are much thinner and less 'compressible' than ordinary weatherstripping, and are designed to be worked into the corners of the lid in a very specific way when installed.  Also, the edge of the can itself is relatively 'sharp', and isn't designed to press against anything as soft as ordinary weatherstripping.  It would probably cut into it over time.  I can't imagine trying to use available weatherstripping material to replace it with a hope for getting a seal as good as the original. 

 

Edited by ecanderson

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On 11/8/2020 at 7:32 PM, beerslayer2000 said:

I wonder if household weather stripping would work... either the rubber kind or the foam kind.

 

I doubt foam would hold up. Ammo can seals work because the lid is clamped down, squezing the thin rubber gasket to keep a seal. Foam would crumble away after a while.

 

A thin strip of silicone sealant might work. I'd try it, but all my gaskets are intact right now, and I'm not gonna break what doesn't need fixing.

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You won't be able to keep the silicone uniform enough to provide a seal anywhere near as good as the original unless you've got a way to maintain the thickness somehow. 

If you really want to keep the water out when it's left upside down in your cache space, the rubber stripping from McMaster plus a little of that silicone to deal with any gaps between the pieces is still, to my mind, the best way to go.  Then again, as cheaply as these cans can be had from surplus sometimes, gotta wonder if it's worth it to rehab one unless there's already something else special about it (camo, locking tricks, etc.),

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On 3/9/2020 at 5:01 AM, kunarion said:

By the time my ammo boxes seals fail, I'm planning to replace the whole box.

That's what I was thinking.... I can't recall ever seeing an ammo tin leak (that had been closed properly), and I seriously doubt people around here have been slipping in to replace their seals??

 

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I used a strip gasket successfully on a can where fire only damaged the lid seal.  It's labeled Gore-Tex joint sealant, 5/8" x 15ft,  100% virgin TFE Fluorocarbon.  Googling this I find that a roll of this product will run you about $385. Likely not the way you want to go =:-o

However,using those search terms I find similar products at 1/2" - not Gore-tex -  which I think would work, and are a lot cheaper. 

 

Gasket has been working fine since 2011.

 

( The sealant roll was in a storage shed on a property I own, likely came out of a failed orange juice processing plant.)

 

In the moist environments where I hide, mostly cans rust out before seals fail.

Edited by Isonzo Karst
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