No, they are not interchangeable. The .32 H&R Magnum and .32 Short and Long Colt cartridges are not interchangeable. The .32 H&R is a longer case, with a larger diameter than the .32 Short and Long Colt. The .32 H&R Magnum also operates at higher pressures than the .32 Short and Long Colt, so it is not safe to fire .32 H&R Magnum rounds in a firearm designed for .32 Short and Long Colt.