Rflshootr,
Firing a gun with an oily bore creates greater bolt thrust. It increases pressure.
Firing a gun with an oily bore AND chamber CAN lock a rifle bolt SOLID.
It will not increase wear in a barrel, as it is the gasses that do this, not the bullet travelling down it.
I do not know if a cold bore shot with an OILY barrel is slower, have NEVER deliberately shot a rifle with oil in the barrel, did ONCE with one of my 25-06's, blew a primer and locked it solid. Case had the deepest ejector swipe I have ever seen.
Cheers.