I have 'properly' patterned one gun .... that is to say, 5 shots from each (pre dirtied) barrel at 40 yards with a given cartridge, draw 30" circle (afterwards) - count pellets and work out percentage. Honestly - hard work with 6' square paper sheets that catch the slightest breath of wind. Didn't learn much - except its hard to do! Resultant patterns were a little tighter than the bore dimensions indicated, but the cartridge used had a plastic wad.
I have shot about half my guns at a pattern plate during fittings. This was to adjust the stock dimensions to shoot where I thought it should. None of my guns showed any significant difference between left and right, or top and bottom in the pattern centre. Where they shot LOW, or LEFT, stock alterations have been made.
