Ammo cans for tobacco storage

The Ziplocs aren't airtight - if I recall, most folks don't recommend them for more than short-term (2 weeks) storage. Not sure about the seals on ammo cans - if they're silicone, they might work pretty well.

Whelp.... Let me see, I have a lot of experience with steel ammo cans starting with a 1950s can marked .50cal/B52 to nearly present day NATO issues. I store, well, ammo in them. It never occurred to me to store tobacco in them. I think the reason is that there is an omnipresent stench of some military grade preservative or desiccant or something that is almost an overwhelming smell in every single can. I can take out a box of ammo that did not have that smell about it when I put it in, and when I open it up again it smells strongly of whatever that is. My fear would be that my beloved tobaccos most likely would take on that smell and I could not be rid of it... Like a military grade ghosting so to speak. It might be one of those things that bothers some people and not others, I don't know. But personally, I would not store my tobacco in those cans for that reason. I have not yet checked out any of the high impact plastic ammo cans yet... Maybe they might be better in that respect. Good luck though... You couldn't get anything tougher than those good old ammo cans!!

Incidentally, I forgot to mention: I have always found that Ziploc bags are permeable, tobacco-wise. I bought a selection of bulk blends from PAndC once that included a large bag of Larry's blend. Every other tobacco that I had smelled like Larry's blend by the time I got it home. YMMV.

I've been keeping a bunch of tins and bags (and pipes) in ammo cans for a while now. Granted these are Canadian ammo canisters, but I haven't noticed my pipes coming out wth any funny smells (other than the smells of pipes and tobacco, which I keep in an ammo can in order to contain those particular smells).
Bags still dry out, the volume of the can is still way too big to keep the moisture in the bag.

It does a great job of containing the smell of a tobacco stash though, the smell I get every time I open it is fantastic. That being said, it seems like nothing actually has a perfect seal, even my mason jars will strongly scent any container I keep them in, and that means there is still exchange through the seal on those lids. Keeping those in another airtight container should theoretically improve long term srorage even further. I actually don't have any jars or tins stored in open air (most of it is in an ice cooler for insulation from winter temperature swings).
Now if you were to stuff a can full to the brim with loose tobacco, that would probably keep reasonably well if the entire volume is filled with tobacco (again, not counting any smell from the paint). A bag of tobacco the same volume as the can wouldn't be much different.

It would be hilarious to see someone filling a pipe with some OTC blend straight out of an ammo can.

I'd say just go with mason jars, they're tried and true.
No idea about "ammo cans". The only guns I own are the ones attached to my shoulders.

I would avoid military surplus Ammo cans for the reasons noted by @jerwynn.

Both Plano & MTM make waterproof plastic (polypropylene) 30 cal-sized cans; MTM also has a 50 cal-sized can.

Both brands are available at Amazon, & Plano is also found at Midway USA, & Dick's Sporting Goods (these have the best prices).

I use them for storing tins in the cellar. They are lighter, more portable, & more airtight than coolers. (I also use 3 & 5 gallon buckets with Gamma Seal lids for Mylar-bagged bulk tobaccos).

Traveler:
I've been able to re-purpose several ammo cans - with some Spanish cedar and pretty cool homemade humidifiers - into very serviceable, poor man cigar humidors.
Please don't do that with your pipe tobacco. Mason/Ball jars are just too cheap: whether new from Walmart or 2nd hand at the Goodwill/Salvation Army stores. (Just buy new lids, okay? They're even cheaper.)
Fnord

Maybe my cans don't smell bad because they were new when I bought them.

A brand new can sealed from the factory smells of the cardboard boxes that cartridges are packed in. It doesn't take very long for this scent to dissipate. I've had some that are full of rust at the bottom, and others that have had water stored in them are vile enough to gag a maggot. All depends on where the can has been. I wouldn't store loose baccy in them, but sealed jars or bags in a can should hold up great.

Even if the can is new and doesn't smell of oil, if it is one of the newer plastic ones, I would still avoid it. I find those ones stink of plastic and will infiltrate your tobacco.