Yup,
I've had this a few times with various aircraft I've been sent to ferry back. It's amazing that for all the requirements for self locking fasteners around a plane, these screws are not locked at all in most cases. The odd time you'll see "witness paint" on them, though that fills in the slot, and makes them hard to remove for maintenance next time.
On one occasion, I had no choice but to tie together the mag case with plastic tiewraps. Not approved, but it worked fine.
Yes, preflighting the security of the mags, in the whole sense, is a good idea!