[Unclenick]

The official difference in height is 0.009", but the tolerances are so generous that the minimum LR primer height and the maximum LP primer height overlap by 0.003". So a physical fit is possible with some lots. However, large rifle primer cups are typically made of 0.027" cartridge brass (C2600 brass). The large pistol primers use about 0.020" cartridge brass, IIRC. But even if I'm not recalling the exact pistol primer thickness correctly, it is thinner material to enable the lower energy firing pin strike from a handgun to set them off reliably. That thinner brass can pierce at rifle pressures, and a pierced primer cup results in high pressure gas impinging on your bolt face, which cuts little pits into it. There is a lower but real possibility of a complete primer blowout that damages your bolt or your extractor more severly.

Anyway, the bottom line is that there is a reason for primers being labeled for pistols or for rifles that isn't just about their exact size or how big a spark they make.