Tim, that's awfully nice of you (as per ususal!
).
I'll check with Numrich after I pull the other one out. They do list a replacement but I'm not confident the schematic they have for the 155 is "picture perfect". I'll let you know.
As an aside, I now am leaning heavily to the spring being weak. To test the firing pin I removed the barrel, cocked the action and placed a coin on the receiver over the firing pin hole. Did it with the Shikari and the SB2. The Shikari shot the coin a few feet up, the SB2 nearly put it through the roof!
Seems the spring is the culprit.