Yes it will affect accuracy.
How much depends on what you shoot in it.
.45 Colt bullets are either .452" or .454".
And .452" bullets in a .458" throat is Not 'minor'!
.45 Colt factory loaded 250-255 lead RNFP loads generally use very soft hollow-base bullets.
So the bullet base expands when fired to fit the over-size throats, then swages back down in the forcing cone.
Jacketed .452" bullets may shoot O.K. too, if they have a long bearing surface to keep them in a straight line until they get out of the cylinder.
Reloads using solid base cast bullets may present a severe bore leading problem due to gas cutting melting the sides of the bullet base while getting through the oversize throats.
rc