I have owned quite a few surplus rifles over the years, and your letter reminds me of my first rifle, a Spanish Mauser 98, and my fears about having it checked as I was 18 years old at the time.
I did have a gunsmith check it before I fired it, but after that I made a rule that if in doubt about ammo or the rifle, bench it, making sure it is safely aimed down range, and pull your face to the left and away from it when firing the gun. If the rifle explodes, it usually will blow up and to the right, or back, either way your face is away.
I still use this method when test firing the first round of questionable military ammo, or a new surplus rifle. I also scrutinize the fired case to check it for bulging, splits, etc.
I have owned 3 Mosin Nagants, and they are average in recoil with the steel butt plates, I use a slip on butt pad to make em' smooth shooting in the recoil dept.