Well since you already picked up the Chrony that was going to be my first recommendation, as it is a needed piece to tune these guns. I have used 22 lr shell casings for different spring guides in the past. Just double checked, and it did fit in the hammer spring. I can drop you one off for free when we meet up. Oh, and the Mellon PA's are very nice, as you can change the hammer spring without removing the adjuster from the gun, just the adjuster screw.Casey