I believe you already have your answer, the strait wall hulls have a larger and different shaped area above the base wad where the powder burns. I guess it coud be best described as a strait cylinder, compared to a cone shape in tapered hulls.
I am surprised that the load is the same in a strait walled hull. Typically it takes more powder in a strait walled hull to achieve the same velocity.
I assume you are talking about Federal/Estate hulls. Be aware that many of these strait walled hulls have paper base wad, and can really only be reloaded a few (4-5 times) max. Federal also had some issues with the brass coming off of reloaded hulls when they were fired/ejected. Other European shells/hulls are hard to get consitant crimps.
I am surprised that the load is the same in a strait walled hull. Typically it takes more powder in a strait walled hull to achieve the same velocity.
I assume you are talking about Federal/Estate hulls. Be aware that many of these strait walled hulls have paper base wad, and can really only be reloaded a few (4-5 times) max. Federal also had some issues with the brass coming off of reloaded hulls when they were fired/ejected. Other European shells/hulls are hard to get consitant crimps.
