There is plenty of risk firing old ammunition. The pressure goes up as the gunpowder deteriorates. Given that a reasonable lifetime for single based powders is 45 years and double based is 20 years, your ammunition is very old.
This is something that is very well known which is why militaries discard old ammunition. It is unsafe to store and unsafe to shoot.
Heat accelerates the deterioration of gunpowder, so for accelerated propellant tests, they heat the gunpowder. As this test shows, combustion pressures will rise after aging.
INVESTIGATION OF THE BALLISTIC AND CHEMICAL STABILITY OF 7.62MM AMMUNITION LOADED WITH BALL AND IMR PROPELLANT
Frankfort Arsenal 1962
3. Effects of Accelerated Storage Propellant and Primer Performance
To determine the effect of accelerated isothermal storage upon propellant and primer performance, sixty cartridges from each of lots E (WC 846) and G (R 1475) were removed from 150F storage after 26 and 42 weeks, respectively. The bullets were then removed from half the cartridges of each lot and from an equal number of each lot previously stored at 70F. The propellants were then interchanged, the bullets re-inserted, and the cases recrimped. Thus, four variations of stored components were obtained with each lot.
Chamber pressures yielded by ammunition incorporating these four variations were as follows. These values represent averages of 20 firings.
Personally, I would not risk damage to any autopistol I own by shooting a box of 65 year old cheap surplus ammunition.