Silica Gel Desiccants
 

Regarding silica gel desiccants placed inside of ammo can. How often do you replace them, and how long will each last?

Iirc, it depends on how often you open the container and the relative humidity while open. When I was researching food storage about three years ago, I believe I read one packet in a coffee can size container would be effective for up to an hour exposure of opening. It's been awhile since I read that.

I'm sure bkt or c3 will come along and straighten out my memory and give you the goods.

I use kitty litter in my safe in a perforated coffee can. Once a year or so, I will pull it out and bake it in the oven for a half hour. I live in the tropics and you won't find any rust on my guns.

I suspect it would work well in ammo cans too.

Yep. Once sealed, it absorbs moisture in the air inside can, no more gets in. You can reactivate by baking at low temp. Stuff I have used has a color indicator mixed in, tells you when you need to recharge. Depends on size of packet, size of container, ambient humidity, and how long you leave can open. I have some 20mm cans that are BIG!

Re: kitty litter- will work, but important note- get it BEFORE kitty does. :p

I also keep a bag in the trunk for emergency traction on ice.

There are some out there as well that are designed for specific RH levels. Sold to the museum art community and widespread in the cigar world. Usually sold as 60 or 65 percent RH. Works great in a humidor and also in the safe. Should be good for ammo too.

What about vacuum packing ammo. Any negative side effects ?

Great question. I've wondered about vac sealing small caches of ammo the can and bury in a few shtf rendezvous locations.

The last time I tried to put the old bag in the trunk, she used a tire iron on my a$$.

Almost everything is coming with those packets of dessicant. Grab the ones that came in the box for the wife's shoes. At my house, that is a regular change out.

Corrosion Prevention
 

Silica gel is a granular form of silica that is made synthetically from sodium silicate. It is non-hazardous and can absorb upwards of 40% of its weight in water vapor at 100% humidity. It is a solid substance that is extremely porous, making it capable of absorbing high levels of moisture, it has the highest moisture adsorption capacity of any commercial desiccant making it one of the most effective ingredients for products designed to provide corrosion protection during transportation and storage.

In cases where moisture needs to be eliminated entirely, the use of powerful desiccants such as silica gel may not be enough. To that end, moisture barrier bags can provide the level of protection required. It is often used in Military Packaging.

I make my own with kitty liter. For $6, I get 100 (or 200, forgot how many were in there) coffee filters and 4lb bag of kitty liter. Ive had them in there for a few months now, only opening for less than a minute here and there. I plan on making more and replacing them soon.