Like most of us here I have to buy what's on the shelf, if somethings on the shelf. Magnum pistol primers are the most common around here, with magnum small rifle making a showing too.
In my Ruger bolt gun chambered for the 7.62x39 I need to use something besides standard Large Rifle primers just to conserve primers for my .270 Winchester. So I loaded and shot a few 10 shot groups using Federal Large Pistol Magnum and Winchester Large Rifle primers. I also loaded CCI Small Rifle primers against Federal Small Pistol Magnum. With a charge of 20gr's of IMR 4198 and using Arsenals' 312-155gr boolit I ended up with these groups for velocity. W-W brass for the Large and Hornady brass for the Small.
Large Rifle- 1761 fps
Large Pistol Magnum- 1693 fps
Small Rifle- 1693 fps
Small Pistol Magnum- 1692 fps
The small primers gave the most concentric groups so I'll work more with them.