Tim, if it were my gun, I do not think I would worry about the TM damaging the barrel, or the PSI being to high for 1948 gun. Chances are it has been shot with heavy loads sometime between 1948 and 2017. New stock might be a strong indicator of that. However I would sure pattern that load. You might find that a lower velocity shell will put a significant higher number of pellets in the pattern. Bonus being a bit easier on the gun. Good luck. Pattern kills. Dk