Another reason for the shot limits on modern DSLR's is the amount of buffer and processing speed. I suspect it's the same with phones. It's possible for the sensor to expose images faster than the app can process the large RAW files into the resulting jpegs. When the buffer fills up, it stops shooting (or may just drastically slow shooting to match processing speed in the case of a DSLR). So it may not be physically possible to shoot 300 images in burst mode. At least, not without a slow down of the actual shooting speed.
Something else to consider is image quality. I noticed on my old G4, images shot in burst mode were noticeably lesser in quality than the single shots. I don't know if this is true across the board, but is a trade-off you need to be mindful of if it applies to you.
You may want to search for introvolometer apps. These are meant more for time laps photos, like once a minute or hour for however long you want. These may help you get more shots, but they aren't really meant to be a burst shot app. You may not get them to shoot as fast as you'd like.