Then it may be the channel in the drum was not drilled to speck(to small) from the factory... which isn't the first time it has happened. Also have seen the hole in the drums drilled on angles and not very centered.
Not on the drum but on a T/C my brother bought many years ago had a nipple that wasn't drilled all the way through. Drilled it the rest of the way and 'presto', it shot.
All components being correct, you should be able to shoot reg. 11's in the CVA.