MTM/Case-Gard makes good products.
I would consider these MTM/Case-Gard plastic "50 Cal" ammo boxes to be a good deal at the regular $9.99
But they are a steal on sale at $7.99 shipped Prime.
https://www.amazon.com/dp/B003TNV46O/
Those are the green colored ones, I prefer the black, but green is what is on sale now.
I have loads of GI M2A1 surplus metal boxes which I use for long term storage and use these plastic boxes in a supporting role.
That being said these make a good seal, plus due to the domed lid hold
more than a GI can will, they have two lock holes, and if stored in a climate control environment where the greater thermal expansion of polypropylene vs steel is not a concern then they are a viable alternative to GI boxes.
You can pack them with 30 lbs of ammo and when picked up they do not flex or feel less than sturdy. Although I would not go swinging them around to test that.
Like I said good deal at $10 better at $8.
In this photo there are four cartridge boxes laying flat on the bottom below the ones standing on end, for a total of 20 boxes (1000 rounds).
:emoji_tiger: