What constitutes a different frame size I suppose varies as to how one loks at it. Note in the above frame dimensions the "Bar" is identical from .410 through 12ga. The standing breech & firing pin locations vary according to gauge. Both Lefever & Parker changed standing breech & pin spacings even within the same gauge for different weight bbls. This was how they came up with so many frame sizes. I believe that Lefever had three different Bar sizes for 20ga through 8ga.
Its always ben a mystery to me why most will say that all the Stevens 311s were built on the same frame size, yet even they modified the size of the standing breech & pin spacing for at least the .410. Yet if Smith, Lefever or Parker does essentially the same thing we say they used a different frame.
