I know this was addressed a long time ago. I have the specifics someplace. It actually can be confusng to simply refer to 12g AA hulls as "old style" vs "New style".
The original AA hulls that we geezers grew up with (and loved) were one piece compression formed plastic hulls with Brass (or heavily brass coated metal) rims.
They loaded easily, and many times, before eventually wearing out.
usually the crimps would get weak &/or split &/or melt on the edges after MANY reloads (If you REALLY pushed it).
This is a fairly expensive way to make a hull.
About 10-12 years ago, or so, the bean counters got involved and they beagn playing with "new/improved" plastics but kept the original physical design. I remember that there were 2-3 itterations of this "improved" plastic over the next few years. This was the era of the early light colored "silver bullet" handicap loads and others that had a well desrved reputation for splitting lengthwise down the side as well as other issues affecting reloadability/longevity.
These plastic formala changes, with original one-piece design, would also be called "new style" (or some words best not mentioned in polite company) at the time.
A few years back they switched the design to a less expensive 2 piece plastic hull/base wad. I believe the plastic formula may have evolved a bit too at that time.
The recipes were ESSENTIALLY the same for most loads but might differ slightly dependng on componenets (check the books).
The newer (HS?) 2 piece hulls caused many of us some grief when they would crush and crumble during reloading.
It would happen to me on a VERY regular basis making modest pressure 1oz loads with Win12SL/Claybuster clones. I found that the powder wads would routinely catch the lip between the hull wall and the top of the seperate tapered base wad causing the crunch. I also found that I had to adjust the top/final crimp to try and get a decent non-crunch closing of the shell. It was a REAL PITA to get the press adjusted so that it could load the new 2 piece AA hulls as well as older ones and Remingtons (never completely successful).
Like a lot of people, I have found the new 2 piece AA hull to be a real pain to load with a lot of rejected/crunched ones. I also have been very unhappy with the way that the crimps refuse to stay closed even with the first reload.
I have switched to using Remingtons. The STS/Nitro hulls are great and even the gun club ones load better that AA. They use the same recipes (at least for my purposes) with very slight (usually lower) pressure differences.
Just my personal observations FWIW. (your results may differ).
The new/improved 2 piece hull design has now been adapted to most (all?) of the other AA gauges and designated HS(High strength).
It probably would be best to refer to the one-piece compression formed (original design) and the two-piece HS style (newer design) hulls for the sake of reloading.
JMHO
