I'm about to turn 18, and right now I have a Bushmaster XM-15, Winchester Defender, and Ruger 10/22 all registered to various family members (over 18). I would like to change the registration over to me when I turn 18, but don't quite know how to go about this. Does anybody know where I should go, and how much it will cost? Thanks...

What registration? There is no registration. Their names are on the 4473's, and yours isn't. Count your blessings. Register nothing.

Oregon doesn't have gun registration, so there's nothing to change.  Your family members' names are on the form 4473's, but that doesn't really mean anything.  If they purchased any of those guns after the 'instant check' system was implemented, then the Feds have records that they bought them.  However, that is still meaningless (so far), as there is no federal 'registration' requirement.  If you are now 18, just get the guns from your relatives- there is absolutely nothing that has to be done to 'transfer' the guns to you.  Forget about it and enjoy your guns.

Don't worry about it unless they were straw purchases and you are not elegible to own a firearm.