You should use 270 nm to quantify core histones, provided your concentration is sufficiently high. Molar extinctions are provided in an old Luger-Richmond paper.

Dimitar Angelov cant use 270nm... other proteins also absorb at that wavelength

Almost all molecules, including many buffer components and all proteins (peptides, AAs), strongly absorb at 205 nm. Noteworthy, if you want to quantify histones the best and quick way is to further purify them by acid extraction (TCA precipitation) before quantification by OD measurement. By the way, my recommendation for 270 nm is because the molar extinctions of core histones at 270 nm are known.