Please take note of an experience that I had:

A few years ago I built a sporter for myself using a Siamese action, .45-70 caliber. I kept it for a while and sold it on Gunbroker. As I was prepping the rifle for shipment, I checked the chamber and closed the bolt - firmly, but not violently. To my shock and dismay, the cocking piece popped off and landed in my hand! Since the bolt was closed, and the striker (firing pin) was fully forward, the bolt was locked and couldn't be opened. Upon some consideration, I passed a dowel down the bore and depressed the nose of the striker enough to allow the bolt to be opened.

Upon examination, I saw that the failure originated at the root of the last lug of the striker, where the cocking piece ended: this is the area of maximum bending moment, and the area most likely to fail. The inside corners of the lugs were made with minimal radii, i.e., they had very sharp corners, ideal stress risers. The failure appeared to be a brittle fracture with little evidence of ductility. Fatigue did not appear to be a contributing factor.

I quickly obtained a spare striker from Numrich and was able to send the rifle on its merry way. Before it went out, however, I ground and polished a generous radius in the roots of the lugs to alleviate stress-risers. During research, I found that early Mausers had sharp corners but later ones were generously radiused. Maybe this had happened before?

If I had been shooting the rifle, the falling striker would have probably ignited the cartridge while the bolt unlocked. That would have likely spoiled my morning; it would have been worse had it happened to the new owner. I don't know with certainty that all Siamese actions suffer from this fault, but one would be wise to check.