Yes, LP and LR primers will physically interchange. They are of the same dimensions.
Small Pistol primers have a shorter cup than Small Rifle primers.
Powder suggestion for those reduced velocity loads. I really like Titegroup for this application in 41 mag and 327 Fed reduced velocity loads. Beware, it will use a small volume of case capacity and can be easily double charged.
LP and LR primers have the same diameter but different heights. SR and SP primers are dimensionally the same.
