Re: Handguns....just curious
Small Rifle and Small Pistol primers are dimensionally the same - I use SRP's in my 357 Mag Freedom Arms revolver and have done so in other 357 loads before too.
It is also common practice in many of the high pressure pitol loads used for open class IPSC shooting (9X23, 38 Super etc) and some guys do it in 40 S&W too. And yes, the 454 Cassul is designed to use SRP's.
THe cup is generally harder / thicker and is less inclined to "flow" or pierce with high pressure loads.
Large Rifle primers and Large Pistol primers are not the same "height". If I recall the LPP's are shallower.
I've seen comments that there is no detrimental effect, but obviously there would be a potential problem if the base of the primer were standing proud of the case and dragging on the recoil shield or something.
I'm not sure if your comment was based on how "hot" the primers are, or on dimensions.