I can see what you mean, even in the small pic. What you are suggesting about the grip servering as the open/close breech lever makes sense to me. Here are some pics showing the weapon from various angles, including a close up of the breech and chamber: antitank.co.uk/german1.htm
just add the http, www and such. Apparently I can't post url's :(
Even better pic of breech and sights:
yeah, i pulled most of those off google. Still doesnt show how the breech operates though.