Howdy
Just to clarify things. Injection Molding usually means plastic parts. I don't think any of the parts inside the action of a modern S&W are plastic. S&W uses Metal Injection Molded (MIM) parts. Not the same thing.
Injection Molded parts are formed by injecting heated plastic resin into a mold under pressure. When the mold cools, the resin hardens into the shape of the mold, then it is popped out of the mold. But this is usually a process used for plastic parts.
Metal Injection Molding is a multi step process for forming metal parts with molding equipment. A slurry consisting of powdered metal suspended in a binder is heated and injected into a mold. When the part cools it is considered to be 'green'. The metal particles are held in position by the binder, but the part has no strength. The part is then treated with solvents and heat to remove a portion of the binder. At this stage the part is called 'brown'. It still has no strength. Then the part is heated to a temperature not quite high enough to melt the metal, but high enough to bind the surfaces of the metal particles together. The finished part then has almost the same strength as a conventionally machined part. As with conventional injection molding, there is some shrinkage from the green part to the finished part, so the part is molded oversize to allow for shrinkage. MIM is used because even with all those extra steps it is still more cost effective than machining forged parts.
The process Ruger uses for their cast parts is Investment Casting. Do not confuse Investment Cast parts with conventional Die Cast metal parts. Investment Cast parts are much stronger, than conventional die casting. Investment Casting is similar to the old Lost Wax process used by jewelers for centuries. A wax positive of the part is made and nested on an armature with many other similar parts. Then the wax parts are coated with a ceramic slurry. This creates a mold for multiple parts. Molten metal is poured into the mold and the wax melts and runs out, hence the name Lost Wax. The parts are then broken out of the mold, the mold is sacrificial. Ruger uses high strength alloys for their Investment Cast parts, and after they are broken out of he mold they are heat treated for strength. Ruger DOES NOT make cylinders or barrels from Investment Castings, these are still machined from solid stock. They do make frames and most of the internal parts of their guns from Investment Castings. Some of the Investment Cast parts will have some secondary machining done to dress critical fit areas. Look at where the barrel screws into the frame of a Ruger and you will usually see milling marks left behind from truing up the face where the barrel butts up.
I am a traditionalist, and I like guns made the old fashioned way. But even my oldest three screw Rugers have Investment Cast parts in them. And they have coil springs instead of the traditional flat springs. I have no problem with Investment Molded parts or coil springs in Rugers. I only own one S&W with MIM parts, a model 617. All my other Smiths predate MIM, most of them by many years.
But you know, I'll bet when Colt first started mass producing revolvers in the mid 19th Century there were a lot of traditionalists sitting around griping about the 'good old days' when all guns were made one at a time from scratch. Colt was revolutionary (along with several other 19th Century gunmakers like Winchester, S&W and a few others) in that they embraced the methods developed by the Industrial Revolution to mass produce firearms. Other countries, Great Britain being among them, did not and continued to produce firearms and other products using highly skilled craftsmen. The 'American System' as it was called, clobbered all foreign competition in everything from firearms to watchmaking. The result was affordable, quality, mass produced products.
Progress marches on. If you want to stay stuck in the past, then by all means gripe about modern technology. The bottom line is, if guns were made 'the old fashioned way' today, meaning a lot of hand fitting of forged and machined parts, they would be out of the price range of most of us today. That's why Rugers are so much more affordable then Colts. Investment Casting has driven the cost out of parts that used to be machined from forgings.
And there is certainly something to be said for modern processes. When I go Cowboy Shooting, I shoot a pair of 2nd Gen Colts. But a pair of Rugers goes along for the ride as backups to every match. Twice, over the years, I have had a failure in one of my Colts, usually a broken spring, and I have had to fall back on my Rugers. The simple fact is, even though Colt is still producing the SAA almost the same way as they did over 100 years ago, the manufacturing processes are outdated. Machining the bolt of a Colt is a multi-step process. Part of Bill Ruger's genius was driving the cost out by replacing it with a simple stamped part, that probably only costs pennies to produce.
Sorry to be so blabby, but this is a pet peeve of mine. If you want to buy old guns, and I certainly buy lots of them, my oldest S&W was made in 1870, be sure you understand why you are buying old guns. Is it because you genuinely believe they are better, or do you just like old stuff?