What is the difference between a single and double stack mag?

Quoted: Single stack mags are for rifles that are nuetered so that they cannot accept a standard military double stack magazine.

Another way of putting it:  The rounds rest on top of eachother in a single stack mag, whereas the rounds are staggered in a double stack mag.

Sly's cheesy diagram:

Single stack=
O
O
O
O
O
Double stack=
0-
-O
0-
-O
0-
-O
0-
More rounds can be fit into a staggered "double stack" mag than a single stack mag.

HTH-

Sly

eta: The damn diagram keeps showing up w/ both as SINGLE STACK! AAAARRRRGGGHHH!!!

eta2:  I had to add dashes to the damn O/0 to make it look close to right.  It is damn cheesy!

A little back ground on this is that this letter came out April 6,1998 banning the import of rifles that can use a magazine that holds over 10rds.
www.atf.gov/firearms/assault/treasrelease.htm
To comply with the new import restrictions the importers of AK rifles contracted with mfgs. in Romania to produce the models Romak 991 and WASR-10,Egypt model MISR-10,and Hungaria model SA-2000. The hole in the bottom of the reciever for the magazine of these models was not cut as wide so they couldn't use the double stack magazines but only use the narrower single stack magazine. As you can see in the example in the post above the single stack mags are about 1/4" narrower than the double stack standard AK magazine due to the way the cartridges are stacked in the magazine. Century Arms mills out the magazine opening in the reciever of single stack rifles they import to use double stack mags and adds US made parts to comply with this law.
a257.g.akamaitech.net/7/257/2422/14mar20010800/edocket.access.gpo.gov/cfr_2002/aprqtr/27cfr178.39.htm
So this is why there are  Romanian model WASR-10 rifles available on the market that use single stack or double stack mags.

Thanks for the explanation folks.  I particularly like the diagram  Will the single stack work in a rifle made for doublestack?

Quoted: Thanks for the explanation folks.  I particularly like the diagram  Will the single stack work in a rifle made for doublestack?

Negative.

If you were to get a single stack rifle you could add the correct count of US parts to allow opening the single stack mag well to accept double stacks.  See the build it yourself forum if that's the route you wish to go. ar15.com/forums/forum.html?b=4&f=51

Also the AK Referrence: ar15.com/forums/forum.html?b=4&f=93

Sly