This is irritating.  After all these years, I'm finally sorting out ammo by type and caliber in their own cans.  Except there's a problem.  CCI/Speer boxes aren't the same size as Remington UMC or Winchester or Federal.  Doesn't matter if it's .22LR or .375H&H, everyone has different sized boxes for like calibers.  I'm looking at 4 manufacturers of .45ACP ammo and there's 4 different sized boxes.  

Anyone have any tips or tricks for storing boxed ammo in ammo cans?

Caveat: except shotgun shells.  Those are all the same size/packaging...which is a completely different issue.

I just dump them loose into the ammo can and add a desicant and close it up. I can get WAY more in there that way.

vacuum pack.  pick the size/quantity you want

I dump 100 rounds into a ziplock freezer bag and tear off enough of the packaging to identify the lot # any anything else that might be useful if a kaboom happens.

You can store far more via this method than keeping ammo in original boxes.

I've mixed different brands of ammo in ammo cans and use sheets of cardboard as spacers.  This keeps the ammo snug so it doesn't rattle around.  I also purchased a large bag (100 pieces) of desiccant packs and place one or two into each ammo can.

In mags. 18 30rd USGI mags per 5.56 ammo can with little movement if any.

try a different size ammo can. that or just buy more. i have a wall of full ammo cans, vary from 30 cal up to 20mm.
btw 223 on stripper clips will fit perfectly in a 12ga 25rd box.

I prefer to keep my boxed ammo in their original boxes. (pehaps it's OCD)

Some 5.56/.223 I put on strippers, bandoleers and pack in cans.
Other calibers, I separate manufacturers into their own cans.
Other than that, I buy more cans.

28 standard 30 round AR mags or 24 PMags with ranger plates and caps will fit in a SAW ammo can.
6 battlepacks of SA surplus 7.62x51 will fit in a 25mm/M242 type steel can.

7.62 ammo can tricks and tips:
A sleeping mat cut to fit and taped inside will fit a Beretta 92, 2 fifty round boxes of 9mm and 2 extra 15 round magazines.
A friend of mine showed me a neat trick on how to make a 'tray' for 8 FAL mags with magpuls in a 7.62 ammo can.  
Without the 'tray', 10 FAL or M1A mags without magpuls will fit snugly.  9 will fit with magpuls but will rattle a bit.  It's also best to store them rounds up to keep the feedlips from getting bent.

The 7.62 cans I'd really like to get my hands on are the British 7.62 ammo cans.  They have a rack system that holds 4 cans.  It's much easier to move 4 cans in a rack than not.

I've also started spray painting can lids by ammo type: shotgun, pistol and rifle.  Except for the Korean and Greek M2 cans, they are going to stay just like they are.  

I'm considering getting a couple of Mk19 cans rhino lined when I get my truck bed done, but I'm holding out for the larger HE-DP Mk19 cans, not the smaller T/P cans.

I'm mostly just lamenting the lack of a standard box size for calibers.  Kinda tempted to take a tape measure and get interior dimensions to see who's hard plastic ammo boxes will fit.  Google is a wonderful thing

Great setup!

With pistol ammo, I just dump it and pack each brand/headstamp in gallon freezer bags, which go into 50 cal cans. I shoot it fast enough that rotation is constant and year+ storage is not a concern.

I can't believe no one has said it yet. Buy all of your ammo from the same manufacturer.

Hold on a minute, obsessively reorganizing your ammo a couple times a year is one of those things that I hate to love...or love to hate or whatever. Trying to figure out how to fit all those different size boxes in just one can is like a prepper's Tetris.

I am amazed no one has ever come out with plastic ammo boxes (Midway MTM, Dillon, etc )that fit the 50 and 30 cal cans.

They would fly off the shelves.

Loose is the way to go

You can fit 3400 rounds of 9mm in a large Cabela's can.
You can fit 2000 rounds of 45ACP in a large Cabela's ammo can.
You can fit 5000 rounds of 22LR in a 50 cal can.