I think that if you create a new site and define the ip range as a subnet in AD Sites & Services and if you create the GPO and link it yo that site, it should work.
You may need to enforce thi GPO because Sites GPO are applied before Domain and OU GPO's.
Don't forget to create a new site link.
Another option would be to use Group Policy Preferences with Item Level Targetting. It's possible to define. Ip range
Hth