I bought a 30/06 rifle in May of 2005, and an MTM 100 round green box and 100 R-P cases in the next few weeks. I've been shooting this gun with cast bullets and SR4759, Unique, IMR4227 and AA#9. I wipe each case clean after shooting it and before putting it back in the MTM case.
The cases have been neck sized, M died and reprimed.
All reloading stuff, these cases included, is kept in an air conditioned low humidity building.
Tuesday I noticed some funny corrosion lines on some cases.
The MTM box has a black plastic insert that holds the cases.
At the top of the black plastic insert the cases, in jiggling around, have a line-a mark; all the way around.
Eighteen of the cases are corroded at this line, and the corrosion is deep enough that it doesn't go away after cleaning the case with steel wool. The corrosion is deep enough that I won't use the cases again.
I've used MTM cases for ?35? years, have 3 other 100 round boxes, just checked the cases and there's nothing wrong.
It's pretty clear that some chemical event has happened here. I've got pictures, don't know how to put them in here.
Anybody else seen this?
joe b.

I am a retired Insurance Claims Representative. This situation reminds me of a series of claims we were presented with by one of our insured manufacturers. The manufacturer made a guitar stand. It was VERY popular amongst owners of fine guitars. The areas of the steel stand where the guitar rested were covered with rubber tubing. It worked extremely well, but had a relatively short life. When clear plastic tubing came into general use, the manufacturer decided to "upgrade" their stands. 

After a few months of use with the new stands, the complaints started rolling in. High end guitars had their finish damaged where they touched the plastic. We paid to refinish a LOT of guitars. This is a case where the manufacuturer was "sandbagged" by a supposedly better product.

Maybe MTM has changed their chemistry and has also run into a problem. I would certainly report it promptly, even it the brass is not terribly expensive. It might save the next people from an expensive problem.

Dale53

I wipe cases off with a clean napkin or paper towel.
I sent the message and photos to MTM and offered to send the box and brass.
I checked 3 other boxes, one bought with the box in question. All with brass in them, no problem.
joe b.

had the same pblm, mine went away when i changed the bullet lube.

..ttfn..grampa..

Here's the reply from MTM:
Here's the MTM reply:
Joe
Thank you for the Email. Over the years we have gotten letters like yours 3 or 4 times. Every time we ask the customer to send the product back and every time we can't figure out what happened. We do know it happens in humid climates like the southeast or the northwest and not with every box usually just one. To express our regrets for your problem I'm sending you 2 new R-100s in green.
If you have any problems please get back to us.
Al Minneman
V.P. Marketing
MTM Case-gard

I think that this is a reasonable reply-what happens is a mystery and looks like a 1 in a million happenstance..
I'll wash any new MTM or other plastic cartridge box very well, and leave it out on the porch for a few days before using it.
joe b.