So I've finally sorted out the issue with my rifle, I initially thought it was the magazines fault the pellets were falling out... But... It was actually the o-ring inside the barrel (where the pellet loads), it was missing completely... I replaced the other two o-rings outside the barrel too and my shot grouping has improved drastically... Just thought I'd mention it here in case anyone has similar issues (because I couldn't find anything remotely similar on the internet)