The recent sale of a 10ga hammer gun included a very interesting letter that referenced a pattern of 200 pellets in a 24" circle at 45 yards. Another member PM'd me saying his hammer 10ga was patterned in the same manner at the factory and a gunsmith told him that was a 40% pattern and the chokes were open, which I believe is incorrect. Very soon after that Chuck Bishop sent me a PM out of the clear blue about patterning at the factory and how it changed over the years. I am hoping he will share that info with the entire group here.
After that discussion I found this article about shotgun patterns and it references a book from the 1950's with a chart that sheds some light on this.
A gun that shoots 70% in a 30" circle at 40 yards is expected to throw a 58% pattern in a 30" circle at 45 yards. Reducing the circle to 24" at 45 yards would mean a pattern much less than 58% would still be a full choke.
http://www.shotgunsportsmagazine.com...story0313.html