The 50th anniversery flattop has the original Ruger grip frame that only lasted a few years when the first blackhawks came out, which is nearly the same size as the old Colt single actions and are the smallest grip frames Ruger makes for any of the Blackhawk and Vaquero line ups ever.

Make sure the grips are the stock grips. They'll be black, hard rubber. If they are, this is as a small as a Blackhawk grip frame gets from the factory. If it has an aftermarket or fancier set of grips they tend to be wider and that might be the problem.

Custom grips can be made of course anyway you want, but they tend to be a little pricy.

The .50 anniversaries are great guns. I had a .357 version and almost opted for a .44 mag, but the barrel is a little longer than I like. I currently have a Super Blackhawk stainless in .44 mag with 4-3/4 barrel, with a Montedo grip frame, which is the same small size frame as the New Vaquero and 50th Anniversary Blackhawks.