Catalysis of the reaction: S-adenosyl-L-methionine + (histone H3)-arginine (position 17) = S-adenosyl-L-homocysteine + (histone H3)-N-methyl-arginine (position 17). This reaction is the addition of a methyl group to the arginine residue at position 17 of histone H3.
histone-H3R17 methyltransferase activity