On the right: 5.56x45mm M193.
On the left: .22 Spitfire.
It's a necked down .30 Carbine cartridge. Performance with a 50gr bullet from a 1:14 16" barrel is remarkably similar to 5.56x45mm NATO from a 1:7 14.5" barrel.
Willard happened to have one in his pocket. He's up to something.