If you wish to be ruled by fear, so be it. Life will always have risks. My personal rule-of-thumb is 20-thousands and up is "safe" for modern shells provided the tubes are in good shape (no deep pits, no bad dents). However, IMHO the real risk of "modern" ammunition in old guns is the shock back through the head of the stock. 100-plus year old wood is unpredictable at best. If screws are turning and gaps are appearing then re-evaluate your use.