I would think that most of the "wear" a pistol gets is from being hammered around by recoil. What wears out on revolvers is the small parts, the moving parts and with enough recoil from velocity you get end shake or the frame spung. Semi auto's get the frame cracked, the slide stop bent, the moving parts worn none of which can be related strictly to pressure but are related directly to velocity and battering.


if the velocity is equal the recoil should be close to equal except the additional recoil added by more powder being expelled thus increasing the mass being ejected. Thus slower powder should increase wear. See recoil calculations that include powder weight at Recoil Calculator

Regarding heat of the powder. Slow powder generate more volume of hot gasses. It would be interesting to see some imperical data on the heat of combustion of different powder. However, slow powder in magnums can cause flame cutting and if one considers flame cutting wear then again the slower powder produces more wear.

Regarding pressure. Fast powder may generate more pressure for the same velocity however I've never seen a gun worn out by pressure, a few KB'd by over pressure but not worn out.

With all that, as others have said, IMO there isn't a significant difference in wear between the slow vrs the fast powder as long as the loads remain within safe pressure levels.