I’ve done a quick search of the forums and it’s mainly just people speculating or saying they read this here and that there.
Can someone please explain or provide a Canon link that describes where the ammunition is stored on the suit?
Magnetic magazines and inside the armour is what the video games use I’m assuming. Minus halo reach, but some of those pouches are what soldiers now days use which for a futuristic game is unrealistic.
This topic and this topic pretty much answer your question. In fact you’ve already answered your own question, it basically boils down to magnets and pouches. Sources include most of the earlier novels, Halsey’s Journal and The Package specifically for internally stored ammunition. As for realism, there have been a whole bunch of topics discussing how the UNSC’s weapons should be way more advanced than they are, instead of being not much better than today’s weapons, I guess you could check those out.
You beauty cheers mate