I have always been a little amazed by the low number of failures in older firearms if they are unaltered, in good shape, and used with loads for witch they were originally intended. I once saw an original matchlock fired with out incident, and when's the last time you heard of a M-91 Mosin Nagant blowing up even though many were made before 1900 and re-barreled many times. For many centuries, making good metal was akin to a "black art" and often methods and alloys were highly guarded secrets. The only way of testing a firearm was "proof" firing. While proofing establishes a basic level of safety, it is no indicator of long term safety. All of the much maligned "low number" M1903's survived proof firing and much use before any problems arose. What scares me more than than the metallurgy in old rifles is a receiver with internal stress fractures caused buy a slightly over sized barreled being installed. It can look like new on the outside and be a disaster waiting to happen.
