The thought that it may be a 9.3x72R S&S certainly is worth considering, but rifles in this caliber are pretty rare and are mostly limited to JP Sauer guns. The standard bullet was 187 grains, as I recall, so the proof for a 13 gram bullet seems to indicate it is not the Sauer round.The Sauer and the 9.3x74R are close enough in case dimensions that they are ,in fact, sometines confused.One that I bought as a 9.3x74R and used with that caliber ammo, for years, turned out to be 9.3x72R S&S.The fact that it wouldn't stabilize a bullet longer than the 286 gr.RN, should have been a giveaway, as should a blown primer. Now, I just trim 2mm and still use 9.3x74R dies to load it. I have heard of others using the wrong ammo also.
Mike