The first of the four repairs I performed this semester was on a Stoeger Condor O/U. The second barrel would not fire reliably. This was an intermittent problem which is always difficult to diagnose. On disassembly, I found the following:
At first glance, everything seemed to be good with no obvious fault in the firing system.
The stock bolt showed signs of cross threading. This was repaired as a loose stock can lead to damage on recoil.
On disassembly of the firing system, I did find that the screw holding the safety detent spring was not tightened properly. Looking at the operation of the firearm, it is possible that this could cause an intermittent problem when firing the second barrel. I tightened the screw, cleaned the firearm, and test fired it with no malfunctions.
One of the skills a gunsmith needs to have is to know how to make replacement parts for firearms. Very often, the repair is on a firearm that does not have replacement parts available. The requirement for this course is to make a mainspring and a bolt spring for an L. C. Smith shotgun. The springs are made from blank spring stock and cut to size.
The next step is to shape the springs.
Once the desired shape for the springs is achieved, the springs are heated and bent to the correct shape. Notice the curves in the legs of the springs.
The springs are then cleaned and tempered in our oven. This can also be done by using any heat source, but care has to be taken not to heat the spring too much as it will become brittle and be prone to breaking.
After coming out of the oven (and cooled down) the springs can be tested. This is merely done by compressing them in a vice. If the do not break and return to their original shape, all is fine. Mine passed the test, even though one of the legs on the mainspring broke. After discussing it with the instructor, we felt that it was most likely due to a small stress fracture in the spring material.