well I have .22-250 on there which has the same size opening for the bullet, you cant fit a very big dowel in there I wouldnt trust it with heavy winter coats. Maybe hoodies/fleeces.
i had to use 3/16" dowels to fit in that hole, and they dont make those in the stouter oak dowels at least at menards they dont have them.
You would need something that could take at least a 1/4" dowel so you could use the oak and then yeah It would work to hold a coat IMO.