Please Help With Identification Cutaway

Asked a question about a month ago concerning a black tip 7.62x54r labeled as PZ that rattled when shaken and was never awnsered. Now that it is cut and posted, bringing it back up. Is this a Argentine 7.65 (.313) spotter loaded in a Chinese 7.62 (.312) x54r case, headstamp 71/58? I’m not a reloader but wouldn’t that be a tight fit for the rifle barrel which could slow down the projectile enough to set it off? Thanks wolfgang