You are fortunate......glad you weren’t seriously hurt. Shooting glasses/eye protection......priceless!
Many years ago I had a somewhat similar situation with the first round out of 20 freshly hand loaded .223 rounds......a load proven for several years. The rifle was not severely damaged, only the extractor to be released. The bolt had to be hammered open....the .223 Rem case had been transformed into a “belted” case!
. I went home, pulled the remaining 19 bullets, weighed each charge ( a double charge impossible, plus I do a visual prior to seating a bullet)....all well. The only thing that I can come up with is that I had a barrel obstruction ( had not cleaned since last outing) ....possibly an insect, such as a “dirt dauber”, had plugged my barrel! memtb