Try an experiment...............
With two de-capped pistol cases (that would ordinarly use a Large pistol primer)...........cap one with a LR and one with a LP primer.
See any difference?
Run your finger on the case's bottom (headstamp area)...........feel any difference?
Aloha, Mark
PS............the basic diameters are the same...........but, some have mentioned a difference between heights. Then not to mention, variations by brand. Thus, the suggestion.
And for liability reasons, I'll add..............
Never mix or substitute components.
Every lot of powder, primers, bullets, brass, and any other components can differ significantly. Different manufacturer's components differ substantially. For example, never substitute Federal brand primers for Magtech, and expect the same results. One primer may be fine with your load, but another brand may cause extreme pressures with the same load. Don't substitute magnum primers for standard primers for the same reason. Just because two brands of powder have similar characteristics, that does not mean they are interchangeable or mixable. Every time you finish with a lot of a component, you will have to back off the load slightly and start over, checking for overpressure signs, just as you did when you first worked the load up. You are in essence working up a brand new load.
Taken from the Magtech web site.