Govt. Model (GI 1911-A1) = 5" Bbl & Full Size Grip (usually 8 rd Mag)
Commander Model = 4" Bbl & Full Size Grip
Officer Model = 3" Bbl & Shorter Grip (1 rnd less). My Kimber UC II is like this.
Some make what is usually refered to as a "Compact" model that has a 4" Bbl on an Officer size frame (such as my Sig GSR).
My hands are not huge, so the shorter grip fits me nicely and I find it easier to conceal. I don't have a problem with the 7 round mag capacity and can carry a full size Govt. mag as a spare ( if I want to).
There are probably other configurations out there that I just don't know about. I have a Para Ord PDA which has an even shorter grip than my UC II and only holds 6+1 Rds. Of course, this isn't a true 1911, since it has Para's "LDA" double action trigger.
