Hi Paul,
It is good to see another Sherman for the campaign.
I have a couple of pointers for you.............Nethier of which are your fault.
On the barrel you will see a step down from where the end of the barrel closest to the turret meets the major part of the gun. This step down shouldn't be there it should be flat like the rest of the barrel. The easiest way to change this is to just sand it off with a light grit sand paper.
Also just a word of warning if you a planning on using the kit tracks make sure your rear idlers (I think thats the name) are securely glued to the hull because the kit tracks are a little short and have been known to pull the rear idlers off. It also helps to have the suspesion units glued stiff so they can't move as this also can cause overdue tension on the tracks.
HTH