the theory behind pistol primers in the 22 hornet, as explained to me... (and I'm only paraphrasing, not quoting any one source)
Small rifle primers are "hotter" than pistol primers. The initial firing (explosive force) of the small rifle primer is enough to begin exerting force upon the bullet before the powder ignites fully. The thin walls of the hornet case don't have a lot of neck tension to help hold the bullet in place. So, in milliseconds, the primer pops, pushes the bullet slightly then stops, powder goes, bullet moves out of case through barrel. Think of it as a slight stuttering effect on the bullet movement.
Small pistol primers, not being as hot, ignite with less force, helping to ignite the powder column without pushing on the bullet, causing more uniform ignition.
Proponents of this theory, I being one, also use a Lee Factory crimp die ($10) to put a slight crimp on the bullet to help hold the bullet in place. I feel this helps build pressure more uniformly. Running crimped vs. non-crimped loads over the chronograph has shown better velocities with reduced extreme spread and standard deviations, with better accuracy to boot.
I have a Ruger 22 hornet and had terrible accuracy from factory loadings. Just loading with lil'gun, good 33-40 gr bullets and rifle primers helped. But since I switched to small pistol primers and a Lee Crimp, it's now an 1/2" gun at 100 yards (all day long, if I do my part. YADA YADA YADA! LOL)
Hope this makes some sense.
bownut