1) It's Winchester 243win brass - deep analysis here might be overthinking it. They're easily replaced and aren't expensive.
2) Loose pockets cause gas vents like that - a slight fail in the seal of the cup to the pocket allows flow, and then high pressure flow jet-blasts a pinhole like you see, and burns your bolt face. Since these were range pick-ups, sure, your boltface didn't take the damage this time, but you have indication of failed seal in the recent past of this brass, so how bad do you want to etch your own boltface with these, just for the value of $3 worth of brass?
3) If you insist on recovering this brass, run a pick around the wall of the pocket - does the tip of your pick catch on the jet burn? In the photos, it looks like the pocket wall is compromised, so there remains a path for the jetting to recur on subsequent firings.
4) If you insist on recovering this brass, gauge the pockets. Are they oversized, or were the primers undersized, or was the load over pressured? Gauging the pockets is cheap, fast, and easy.
I wouldn't personally choose to pit my bolt face for $3 worth of Winchester brass.