Here is the part of the Ohio code which pertains to your question:
2923.16(C) No person shall knowingly transport or have a firearm in a motor vehicle, unless the person may lawfully possess that firearm under applicable law of this state or the United States, the firearm is unloaded, and the firearm is carried in one of the following ways:
(1) In a closed package, box, or case;
(2) In a compartment that can be reached only by leaving the vehicle;
(3) In plain sight and secured in a rack or holder made for the purpose;
(4) If the firearm is at least twenty-four inches in overall length as measured from the muzzle to the part of the stock furthest from the muzzle and if the barrel is at least eighteen inches in length, either in plain sight with the action open or the weapon stripped, or, if the firearm is of a type on which the action will not stay open or which cannot easily be stripped, in plain sight.
(a) "Unloaded" means
, with respect to a firearm other than a firearm described in division (K)(6) of this section, that no ammunition is in the firearm in question, no magazine or speed loader containing ammunition is inserted into the firearm in question , and one of the following applies:
(i) There is no ammunition in a magazine or speed loader that is in the vehicle in question and that may be used with the firearm in question.
(ii) Any magazine or speed loader that contains ammunition and that may be used with the firearm in question is stored in a compartment within the vehicle in question that cannot be accessed without leaving the vehicle or is stored in a container that provides complete and separate enclosure.
(b) For the purposes of division (K)(5)(a)(ii) of this section, a "container that provides complete and separate enclosure" includes, but is not limited to, any of the following:
(i) A package, box, or case with multiple compartments, as long as the loaded magazine or speed loader and the firearm in question either are in separate compartments within the package, box, or case, or, if they are in the same compartment, the magazine or speed loader is contained within a separate enclosure in that compartment that does not contain the firearm and that closes using a snap, button, buckle, zipper, hook and loop closing mechanism, or other fastener that must be opened to access the contents or the firearm is contained within a separate enclosure of that nature in that compartment that does not contain the magazine or speed loader;
(ii) A pocket or other enclosure on the person of the person in question that closes using a snap, button, buckle, zipper, hook and loop closing mechanism, or other fastener that must be opened to access the contents.
(c) For the purposes of divisions (K)(5)(a) and (b) of this section, ammunition held in stripper-clips or in en-bloc clips is not considered ammunition that is loaded into a magazine or speed loader.