I am talking about 308 caliber. If a rifle is designed to shoot the 168 grain, would using 175 grain ammo where the barrel out faster than using 168?  Any difference?  It’s a steyr ssg 69 and I can’t remember the rifling twist

I believe the heavier bullets are longer so more bullet is riding the bore. You wouldn't think the difference in 169 and 175  would be much more wear?

I suspect bullet material vs barrel material has a far greater impact.

Generally a barrel wears out from the plasma between the lip of the case and a couple of inches into the barrel, not because of friction.
It is called a plasma because it is so hot that the electrons have separated from the atoms. This is beyond highly corrosive.

What contributes to barrel wear is pressure, the higher the pressure and the longer the pressure is high the more corrosive the plasma is.
Using a slower powder with heavy bullets reduces barrel wear (by a bit more than a smidgeon).

This thread is on this topic
http://forum.accurateshooter.com/threads/question-does-shooting-heavy-bullets-reduce-barrel-life.3755009/

Throat wear before barrel wear