I was trying to figure out what primers to use in my .327 Fed Mag loads. Ran into something funny. I have a box of Fed 205 primers, called "Small Magnum Rifle Primers". And then I realized I have no idea what a small rifle magnum primer is for... Not only that, but of all the numbers of the Fed primers, only one is used twice. The Fed 200 can be either a small rifle primer, or a small pistol magnum primer. All the Fed pistol primers are 1xx - except for the small pistol magnum primer. Then I was looking in my old reloading book by John Wooters (copyright 1976), where he lists primers. He shows for Federal two small rifle primers, the 200 and 205; no small rifle magnum primer; the large rifle primer 210; the large rifle magnum primer 215; the small pistol primer 100; no small pistol magnum primer; the large pistol primer 150; and no large pistol magnum primer. In my Sierra manual it lists Federal magnum primers, including the 205 as a small rifle magnum primer. Anyway it's strange that the large rifle benchrest primer is called the 210M (derived from the 210 large rifle primer) while the small rifle benchrest primer is called the 205M (derived from the 205 small rifle magnum primer). I'm wondering if the 200 small pistol magnum primer is the same thing as the 200 small rifle primer, just packaged in a different box... .327 Fed Magnum cartridges run higher pressure (up to 45,000 psi) than all other handgun rounds except the .454 Casull (60,000!) cartridge and the .357 Maximum (48,000). You are supposed to use small rifle primers in the .357 Max and the .454 Casull, so I wonder if that makes sense for top loads in the .327 too. Hodgdon data shows the "Federal 200, Small Pistol Magnum" primer.