Trigger Mechanism, will it work?
Since it will be a breech load you must also think of the dead space that will be created by your breech, it may be best to use a very thin breech so that your gun will not have a lot of dead space which will increase the size of you barrel volume, therefore a chamber should have chamber 2: barrel 1 ratio, if not your shot may not be as powerful as you like.
when life gives you lemons... make root beer and leave the world wondering how you did that 