Remove left padding with geometry package

I'm trying to make a checklist for glider flying and I'm unable to tell latex to remove all margins from the page.

This is what my code looks like:

\documentclass{minimal}
\renewcommand{\familydefault}{\sfdefault}
\usepackage[a6paper, margin={0cm,0cm},twocolumn, layouthoffset=0pt]{geometry}

\usepackage{tabularx}
\usepackage[table]{xcolor}
\usepackage[english]{babel}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}

\begin{document}
\rowcolors{2}{gray!25}{white}
\renewcommand{\arraystretch}{1.2}

\begin{tabularx}{\columnwidth}{X}
 \rowcolor{gray!50}
 \textbf{ Pre-Flight } \\
 Remove tail wheel (if removable) \\
 Cap \& Sunglasses \\
 Chute on - straps tight \\
 Check Ballast \\
 Px Briefing / Secure back straps \\
 Secure free objects \\
 Check Instruments \\
 Radio on \\
 Controls (Visual) \\
 Wind \\
 Eventualities (Launch failure) \\
\end{tabularx}
\end{document}

However, this is how it looks:

How do I get rid of the white space on the left side?