In the handloads.com chart on primers, the 5 1/2 primers are listed as small pistol magnum primers. In a box of 5 1/2 primers I see no mention of "magnum". I am getting long in the tooth and can easily be befuddled. I had to print out that chart to cross reference etc. I took a picture of this chart and it is below
I might add that Remington 6 1/2 primers are not designed to be used at some of the high pressures some cartridges are loaded to. They are good for 222 pressures though.