It doesn't fit in the core type Keebler, I believe.
Check your pierce pin block. IF it's a threaded piece that screws into the lower tube it takes the rap4 type, but if it's a brass block held in by a setscrew then it's the zeus types.
By simply running a 1/4-28 tap through the brass pierce pin block of a zeus type, you can convert them to use the excellent phantom pierce pins. These are easy to order and keep on hand as extras.
We play Pistol and we encourage the Few despite the discouragement of the Many.