documentclass[
    draft,
    parskip=full,
]{scrreprt}

makeatletter
renewcommand{chapterlinesformat}[3]{%
parbox[t]{linewidth}{%
raggedchapter%
noindentrule{linewidth}{.6pt}%
par@hangfrom{#2}{#3}%
parkern-.75htstrutboxrule{linewidth}{.6pt}%
}%
}
makeatother

begin{document}
chapter{test}
end{document}