I thought of something similar when I read the explanation. Magnesium? Like the magnesium filaments in old flashbulbs? Like the magnesium used in road flares?
I was thinking more incendiary device than explosive device though.
While we may be getting a little far afield here, it is important to point out that the classic mess hall (pardon me, dining facility) SOS was not creamed chipped dried beef but was creamed ground beef. I suspect it was derived from that old favorite pork sausage gravy on a bisket. Shit on a shingle in this case was an euphemism. The stuff looked like dog vomit, the proverbial dog’s breakfast. Hot and with some seasoning it was pretty good. Cold and without a little good old Louisiana hot pepper sauce it was just dreadful. I have seen kids just back from two week patrols turn down cold SOS in favor of C Ration beanie-weenies. I can’t imagine putting that stuff in a field ration.
The history of SOS. 
My favorite MRE meal so far has been the veggie pasta in marinara sauce.
I’ve been told by a OK Army National Guard sergeant (also one of my scout leaders) to never ever trust an MRE with “Chicken” on the label 
Same fellow told me that they stopped packing dehydrated fruit in MREs because soldiers would put it in their canteens with the sugar packet and water, and it would ferment into alcohol (the things you learn in Boy Scouts).
On the few occasions where I was on a camping trip and we had MREs, we developed a sort of economy amongst the scouts based on tobasco bottles, chiclets, and whatever packs of matches we could hide from the scout leaders.
My ex-fiancée was a pilot with the 101st Airborne during the first Gulf War. They had the dehydrated fruit then. She said they’d crumble the godawful crackers into a canteen, add the sugar and creamer from the MRE, and crumble the dehydrated strawberries on top. Add water, and you had ‘strawberry shortcake’.
So what’s to stop soldiers from making hooch with the wet-pack fruit?
I wasn’t aware there was another kind.
The original, mid-1980s MREs were very similar to the LRRP, up to and including the plastic bag that you had to figure out how the hell to tear open. Back in 85-86 I remember the MRE that included the dreaded Pork Patty, a rectangular piece of matter that would make a very adequate backstop for a shooting target. If you recall that was also the year of the big Horn-of-Africa famine, thus propitiating the nickname “Meals Rejected by Ethiopia”…
I remember, one day in mid 1998, while with JROTC, we were fed lunch out what appeared to be a very old case of MRE’s (I had been in JROTC and CAP for over five years, and had eaten many MRE’s, even living on them for 10 days once.) (Also led to the most satisfying shit of my life, 5 days into the trip, but that’s TMI and not for here)
Opened the bag, got the god awful brick o’ spam. I was pissed. Then it got worse.
Out fell a bag of M&M, proclaiming themselves as the official sponsors of the 1988 Olympic games.
I waited until dinner to eat that day…
Well, as promised, I went over to my Commissary and picked up a couple of those ‘Civilian MREs’ I mentioned earlier.
The only reasonable difference I see between the military-issue MRE and this, is that the Mil MRE has a brown, opaque outter bag, while this Civvy MRE is clear.
But, I can clearly see a water-activated heater in mine. This thing is called a “TOTM: Tailored Operational Training Meal”. It must have to do with the marketing or something.
Tripler
Oh look! I got Peanut Butter M&Ms!
Wasn’t there a thread a few years ago by someone who secretly fed his g/f MREs for a ‘homecooked’ meal? And then he later told her that she’d consumed about 6,000 Calories in one sitting?
Or was that something I heard on KROQ?
A friend of mine is ex-Army…actually due to a screwup in when he was supposed to be beyond recall he is now active Army again but I digress 
Anyhow he brought along a case of MREs to one of our Yosemite trips a few years ago and we took them on some long dayhikes. We’re now pretty jazzed about them (not for breakfast or dinner, we like to actually cook) but there is something very satisfying about hoofing up to the top of Yosemite Falls, sitting down and then in ten minutes having a hot, satisfying meal. Plus a beer. I always bring a beer with me The looks you get from folks who have one smashed sandwich and a granola bar are priceless.
The selection is pretty good, we’ve got a couple of kosher folks and even one hardcore vegetarian in our regular group and everyone had a good selection to choose from. The downside is the large amount of packaging you need to haul out. The food is actually pretty good, on par with your average TV dinner.
I love the instructions for heating the entrees up - after you put the heater pack and water in the bag and stuff it all back inside the cardboard box it says “Rest on a rock or something”. We always make sure to look around for an adequate “something”.
Wildguy found MRE’s at our local Ocean State Job Lot once, when I was working a job that I had to bring a lunch. He bought a bunch of them. Most of them were good, but all kinda tasted the same. They were great to keep in the desk when Wildguy was unable to make my lunch for the day. The uwave did a good job of heating them up.
Wildguy also said he used to get C rations when he was a kid. His dad would buy them at the surplus store, and he’d take them on his Boy Scout camping trips. He said he’d always come out a couple of bucks ahead by selling the cigs in the pack to the other guys
Olive
The difference between a TOTM and an MRE is calories. The TOTM is designed for chair-warmers, not active grunts.
Nope, that was here. People got very upset.
http://boards.straightdope.com/sdmb/showthread.php?t=301621&page=1&pp=50