The "Bottle " shape is very common. I used a similar design my first ball bag. However, since then I realized the bag holds too many balls and really is a PITA to haul into the field, unless I reduce the number of balls down to about the same I might carry in a ball BLOCK!
So, the next bag I make is going to be only about 5 inches long, and maybe around 1.5" in diameter, so that it easily holds in my fist. Even with my .62 caliber balls, it will hold more than I will ever need deer hunting in the field. I would rather have a couple of these to use, than ONE larger ball bag. I can leave the extra one filled, back at my truck, or in camp.
With my .50 caliber rifle the small bag will still probably hold way too many balls for any field use. But, It will serve me well on a Hunter's Walk course at the club.
I am thinking of doubling the wall of the neck with extra leather, to give it stiffness, which will help keep it closed should the bag be upended, and the plug fall out. To open, simply pinch the sides of the neck to let a ball come out or go in the neck one at a time. :hmm: