Some magazines have a window along their length, so when you eject the magazine you can see how full it is with a glance. Otherwise, you'd have to be familiar with the weight of the gun or magazine to estimate, or you empty (or fill) the magazine to know for certain.
For the record, I would expect that magazine to be full. There's no good reason not to reload it to capacity during down time after use, and no good reason to think that Wesley used it after getting it from Francis.
Re: Wesley's gun
Some magazines have a window along their length, so when you eject the magazine you can see how full it is with a glance. Otherwise, you'd have to be familiar with the weight of the gun or magazine to estimate, or you empty (or fill) the magazine to know for certain.
For the record, I would expect that magazine to be full. There's no good reason not to reload it to capacity during down time after use, and no good reason to think that Wesley used it after getting it from Francis.