Craft Gunmaking, No compromises, No corners cut, EVER

Monday, January 20, 2020

A New Ejector Segment for an A&A 453

This is a common enough failure with many side-by-side ejector guns, and the part usually breaks at one of two places, either at the end of the retaining screw slot, or the point where the half-shaft meets the face of the ejector.  In a design like this, with an integral guide half-pin positioned at twelve o'clock, failure of the guide pin is less common but it does occur.  The most highly stressed point of the part is where the retaining slot impacts the retaining screw.  This is because when the part stops against the screw, inertia carries the rest of the part onward, eventually failing it at the weakest point.
When ejecting spent shells, the weight of the empty hulls does a good job of mitigating this inertia.  Letting the ejectors trip on empty chambers is another matter.  It's always a good idea when opening an empty gun to place a thumb or index finger on the ejectors before they trip, in order to slow their speed, and prolong their life.  As described above, this isn't necessary when opening the gun after actually firing a shell (or shells).  It will never be a factor to even consider if you're not obsessively compelled to "relax" the mainsprings by dropping the hammers (a practice that has been debunked elsewhere on this blog).  Onward ho.....

The new ejector was blanked from a bar of O1.  From this point on, it is all handwork, except for the retaining slot, which is done on the mill.

The half-shaft is filed up completely by hand in the following manner.
Once I cut the blank from the parent stock, I filed 45 degree (approximately) bevels, then filed the "points" off the bevels.  Once it started looking half-round, I colored the entire surface with a black marker and then ran the appropriate radius gauge down the length of the half-shaft.  That left bright marks on the spots that needed to come down.  The process is repeated until the entire length matches the gauge.
The above filing stopped about .100" short of the root so that I could create the stress relief radius there.
The radius at the root was done by eye, using small,half-round files and polished using wet/dry paper wrapped around a short length of drill rod.

Next was fitting the face into its recess in the barrels.  Once it is fitted and the chamber ID is cut, the rim cut is made using (funny enough) a rim cutter.  Then the radius at the bottom is filed up and it's ready for the machining of the retaining slot and filing up the extraction cam and hammer striking faces.

Once all of the cutting, filing, fitting and polishing is done, all sharp edges are broken in order to ( in combination with the surface finish) deny cracks a place to start.

After heat treating and repolishing, it's assembled and ready to go back into service.

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