.22 Magnum Devastator

March 30, 1981, John Hinckley Jr. attempted to assassinate President Ronald Regan using 6 - .22 Devastator bullets loaded into a Rohm RG-14 pistol. The Devastator brand cartridge contain small amounts of aluminum and lead azide explosive that is designed to explode on contact.
The first shot hit then White House Press Sec. James Brady (Check out Brady Handgun Violence Prevention Act Nov. 30, 1993), which was the only projectile that exploded, in his head. The second shot struck District Of Colombia Police Officer Thomas Delahanty in the back of the neck while protecting President Reagan. The third shot missed, and the forth bullet hit Secret Service Agent Tim McCarthy in the abdomen. The fifth hit the limo window, and the sixth ricocheted off the armor of the limo striking President Reagan under his left underarm, grazing a rib and lodging in his lung, stopping 1 inch from his heart.
On April 2nd, after realizing that the other projectiles can explode, volunteer doctors with bullet proof vests removed the bullet from Delahanty’s neck.

Out standing
Charles.J. Wells (Jack)
SGM. USA. Ret.

Nice sectioning work as usual.

I was under the impression that Hinckley used a .22 Long Rifle round?

First of all, Hinckley used a revolver. That’s not the same as a pistol. Secondly, the name is Röhm, o with umlaut. And last but not least, magnum .22 rimfire does not fit a .22 LR drum, it’s to long (sic) unless of course Hinckley used a magnum drum. Some Röhms however passed my hands. I know a magnum .22, that’s the RG 66. But it is unknown to me Röhm had a RG 14 in .22 magnum.

Wikipedia: Hinckley’s gun was given to the ATF the day after the shooting to trace its origin. In just sixteen minutes agents found that the gun had been purchased at Rocky’s Pawn Shop in Dallas, Texas.[27] It had been loaded with six “Devastator”-brand cartridges which contained small aluminum and lead azide explosive charges designed to explode on contact.

It’s quite possible Hinckley used .22 Devastator cartridges. But I doubt he loaded his gun with magnum rounds, as the post of wolfganggross suggests.