Some rifles will throw first rounds out of an oiled bore, some don't. If one does, consider that the barrel may not be well-tuned to the ammo being used.
It's believed that the ideal situation for a load is when the bullet exits the barrel slightly before the muzzle reaches the maximum vertical amplitude of it's vibration, when it's nearly stopped moving in that direction. That's when minor variations in pressure/velocity don't make as much of a difference in vertical displacement of projectiles (POI).
Tuning to achieve such a condition is accomplished by the handloader, primarily by changing seating depth, but bullet selection, powder selection, charge weight and primer selection can all have an effect.
Folks who don't reload can change ammo brands/types, bullet weights, stock screw tensions, or consider changes to pressure points. Action bedding can also alter or even reduce vibrations somewhat.
I usually clean my CF rifles after shooting and use a slightly damp patch with Break-Free CLP prior to storage. When hunting in November, I usually run a dry patch through the bore, then place a piece of electrical tape over the muzzle to keep the bore dry and protect it from debris. The trapped air ahead of the bullet pushes the tape off prior to the bullet exiting.