One of the things any writer learns is the various meanings of a sentance based on the placement of the word "only."

One failure only, caused by ammo.. Means the was one and only one failure--period.
Only one failure caused by ammo... means simply there was one failure because of ammo--but there could have been many others caused by shooter or firearm.

Good writers know this and will use it to their advantage to create whatever slant they wish to present.