While this would physically work, it may not meet the requirements of the range. If the range officials determine whether or not a load is a "magnum" by reading the headstamp on the case, they may not allow even light-loaded target-type ammo in the range if it loaded in magnum cases. On the very few ranges where I have seen pistol ammunition velocity restrictions, this is the most common method of screening.
Originally Posted by FloridaGuy
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)