Hammer P was a plastic trigger frame, but had a removable grip.
Hammer A was aluminum trigger frame with removable grip.
Hammer plus had an aluminum frame and added a power feed instead of a direct feed.
New Hammer had the body of a Plus but with a one piece plastic trigger frame/45 grip. you can not change the grips or easily mount a bottom line because its hollow. it was also prone to breaking where the screws mounted it to the body.
most A, P, and Pluses came with the brass lined barrels(all spyder threaded)