Battle jackets were originally designed in 1983 for South Africa's R4 (Galil) 35 round magazines, which are similar in size but slightly longer than standard USGI/STANAG magazines.
PMAGs might be a tighter fit in general, and specialized 5.56 magazines such as those for the G36 are not going to double-stack. Consider using PMAGs instead of the kind that link together.
The best possible fit is always going to be the aluminum/steel USGI-style STANAGs for their slightly thinner proportions all around.
7.62 platform magazines, like the case with original battle jackets, largely do not fit in the main magazine poouches. AK mags are too tall, and "Battle Rifle" magazines such as those for the G3, FAL, or M14, are too large or otherwise awkward of a fit.