How many bullets are left in the magazine?
Witness testimony analysis 2 re-presents the sequence of events of 14 Feb based upon the supposition that Johnson's phone time is incorrect (see event comments for rationale). This then allows for the possibility that the 3 loud bangs that the Stipps hear some time after Annette Stipp wakes at 03:02 (less 3/4 minutes) are prior to the 4 shots that kill Reeva, which most ear witnesses then hear. One possibility for this first set of sounds is OP firing out of the balcony doors or bathroom window.
The photo of the magazine at the scene shows us that there are at least 10 bullets (of 17) in it but not whether there are more (except there aren't 17 as can be seen from the viewing hole marked '17' which is empty). If there are more than 10 bullets in the magazine then it is unlikely that the first sounds were gunshots. If there are 10, that leaves open the possibility that 7 shots were fired and perhaps the initial 3 cartridge casings were then removed from the scene (via Reeva's bag being one possibility). This also assumes that OP kept the magazine fully loaded, a reasonable assumption?
As there doesn't appear to be any evidence given on how many bullets are left in the magazine, I've had a go at figuring it myself.
From this picture of a disassembled 17 round magazine taken from a Taurus PT917CS (same gun) we can see that there are 12 complete coils in the spring.
View attachment 62408
Closer inspection of OP's magazine below shows two coils of the spring visible in the bottom right 'viewing hole'. The first is easy to see, and you can see the edge of the second to its right if you look carefully.
View attachment 62409
If the gap between these two coils is measured and then multiplied by 12 (the total number of coils) this then gives us an approximation for the extent to which the spring is extended within the magazine. Add the piece of yellow plastic that is used as a seat for the last bullet (see top photo) and we have an idea of where the bottom bullet sits in the magazine and therefore how many bullets remain.
View attachment 62412
The estimating method is inexact but I come to two conclusions assuming the magazine was full to start with:
1) It looks like there are only 10 bullets remaining in the magazine which implies 7 may have been fired
2) Even allowing for the inaccuracies of this approach it still looks like
more than 4 bullets are missing, which again supports the 7 bullets used hypothesis
Would anyone else care to have a go at this exercise to see if you agree or not?