Jim:
In a recent article, Jerry M. mentioned:
“One more thing worth mentioning is the small rifle and small pistol primers are the same size cups, same as the large rifle and large pistol primers are the same size. The cups on the pistol primers are a little thinner than the rifle, for obvious reasons, most rifle firing pins hit a lot harder than pistols do. I have used rifle primers in pistol rounds, and they seem to work fine. You might run into problems on S&W revolvers, using rifle primers, if you have the spring tension screw backed off to get a lighter trigger pull, but this could also happen with pistol primers, if backed off too far. Men sometime do this for wives who have trouble shooting double action, don’t! Your taking a chance on a misfire when you do this. And never use a pistol primer in a rifle round, the cup is too thin and if the firing pin penetrates the primer, you will get gas back in your face.”
To add emphasis and a clarification to Jerry’s warning: Rifle and pistol primers may have the same diameters, but they don’t have the same height. Using a large rifle primer in a pistol case will cause the primer to protrude above the case head, since large rifle primers are deeper (taller) than large pistol primers. Worst case, a semi-auto pistol (like a Model 1911) could be “slam-fired” or even double (go into uncontrolled full auto fire).
Please use the correct primer for the cartridge you are reloading! – J.B. in Tennessee