Craft Gunmaking, No compromises, No corners cut, EVER

Thursday, November 1, 2018

Sidelock Sear Spring

The patient is an AyA Number 2 SLE with a failed primary sear spring in the right lock.  Luckily, the interceptor performed as designed and kept the tumbler from falling and causing an unintended discharge.  The Number 2 is a straight Holland pattern sidelock, nothing unusual or novel about the design.  So how does something so ordinary warrant mention in my gallery of the weird, odd and unusual?  Well, first off, there are no unimportant parts in a shotgun.  Secondly, because the failed part is a perfect example of how not to make a spring.  I don't know if it was because an apprentice was entrusted to make the part, if it was made just before the weekend or if a bit too much txakoli during lunch played a part but, no matter, let's get on with it.

The original spring.  Now, we all know that the limb(s) of leaf and V-form springs should taper, gracefully and continuously, being thicker at the root and thinner at the extremities so that the entire limb flexes from tip to root.  The maker of this particular part didn't get the memo, however.  The lower limb collapsed right where you'd expect it to do so.

This spring has an integral tab on the back side of the top limb that engages a slot in the lockplate to keep the spring from simply rotating around the mounting screw.  A piece of O1 flat stock with sufficient thickness was selected and the blank for the new part was cut from it.  O1 generally isn't the first choice for forging but it can be done in thin sections (such as a spring), as long as it's done at the proper temperature.  With the crotch of the spring formed, the back side was machined and filed to create the aforementioned locating tab.  Then the mounting screw hole was drilled and the rest of the spring was filed up in the usual manner.

I also filed up the "ring" around the mounting screw hole a bit more artfully than the original.  After fitting it was heat treated, polished (by hand) and the lock reassembled.

The gun also needed a new right side striker because the original was bent, causing it to stick and not retract.  I didn't document that part of the job because we all know what a Holland pattern striker looks like.

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