Good question.
To my knowledge, all WASR's are modified at Century Arms International
(
Century Arms ) and they are known for doing a fast and sometimes sloppy job.
I also own a WASR but I bought the single stack version for this very reason. I wanted to modify it myself in the future.
If some mags fit snug and some loose it will be more difficult to correct this problem. If they all fit the same, you might be able to modify to inside of the receiver by building up the magazine supports somehow. It's all trial and error; I would try to affix a small piece of metal on that little flange called the "magazine support" with a spot weld or very strong Liquid Metal or PC-7.
When this stuff hardens you can drill, tap and sand to shape, and if bonds to most surfaces very well.
After adding this metal, dremel it down little by little while test fitting till you get a nice fit to your Mags.
This is just an Idea I have never tried it or heard of it, although it might work great.
By the way, when I did the woodwork on my WASR it turned out nice, but if you decide to sand it to get the oil off, please wear a mask. I had a bad reaction to the wood dust that was saturated in that strange oil of unknown origin. I then stained in very dark 4 times then I hand rubbed several coats of BOILED linseed oil on to it as well. I didn't want that real shiny lacquer finish like most rifles have, as I thought this would be easier to maintain.
Keep us posted and toss in your photo updates.
Thanks,
Big Willy