For what it's worth...
Back on the old board, we had a discussion at one point about cast parts vs forged parts (or wrought material parts). Cast materials, as they come from the mold, almost never exhibit wrought material properties. They are always weaker due to inclusions and voids in the cast material that cannot be avoided. However, a casting can be HIPed - hot isostatic pressed. The following is what I wrote in my post on the old board:
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In my aerospace world, casting are not often used because we need the much better wrought material properties. However, we do make many more parts now by casting and get much better material mechanical properties by subjecting the castings to hot isostatic pressing (or Hipping, for short). The process involves putting castings in a cold furnace and then pressurizing it up to 2,500 psi or so with Argon. Then the furnace is heated to within a few degrees of the melting temperature of the castings. By the time the furnace is up to temp, the pressure is up to over 15,000 psi. While this process cannot repair an inclusion (i.e. mold sand, etc.) in the casting, it does close all the voids and results in a casting that is very nearly as strong as a forging. Pine Tree Castings (a subsidiary of Ruger) hips all (or most) the castings they make for Ruger firearms. The process is fairly inexpensive if parts are run in large lots or piggy back with a similar material. I have always thought that Hipping might greatly improve the quality of cast lock springs without adding too much cost.
You can also make up very unusual material combinations with this process. A friend of mine got a piece of 1 inch diameter 304 stainless steel tubing and TIG welded a cap on one end. He filled it with powdered stainless steel, powdered nickle, and 0.125 440C ball bearings and then welded another cap on the open end to seal it up. He had it Hipped and when it came out of the furnace it looked like a twisted piece of stainless steel rope. Inside, all the powder and ball bearings were fused into a solid mass of metal. He forged it out and made a knife out of it and etched it. It had the most unusual pattern you ever saw.
Here is a link to a company that does this type of work
http://hip.bodycote.com/?OB=112&POB=266&ID=35**********************************************************************************************
While the throughput for lock castings is undoubtedly very low compared to what Ruger puts out, I believe there are companies that will add a batch of parts to one of their hipping furnace runs for a reasonable fee. Every time I buy a lock, I buy a spare main spring and a spare frizzen spring (no matter who I get the lock from). I have never regretted the added expense as more than a few cast springs have broken in normal use. It would be interesting to test a batch of cast springs against a batch of the same cast springs that have been hipped (both material properties and repetitive flex testing).
