To be clear review the differences in brittle fracture and ductile fracture.
When a low number Springfield fails you will get fragments without plastic deformation. A properly heat treated receiver will deform before it breaks.
If you do not comprehend the differences in the 2 different failure modes you should research the subject. Low number Springfields are junk.
Attachment 182289
Notice where the brittle failure occurs. It happens without deformation of the metal and can result in fragmentation.
Attachment 182290