Gary
The main difference in 416 and 416R, besides the re-suphurization as mentioned by George, is 416R is manufactured under the strictest procedures, insuring a steel that is very "clean", and very exact in it's chemical composition. This allows the steel to adhere to the advertised physical properties while offerring excellent machinability. 416R, developed by Crucible in conjunction with some of the top barrel manufacturers, offers a steel that has excellent machining qualities while maintaining adequate strength and corrosion resistance for the manufacture of precision Rifle Barrels.
The same steel can be bought under the heading: "Steel used for the manufactuer of pump shafts to be used in Nuclear Power Plants".
In the end, though, 416 does have better impact qualities than 416R, but neither one is that good when compared to the Martensitic Stainless Steels, (410, 420), the age hardening, (precipitating hardenning), grades such as 17-4 and 15-5 PH, and standard alloy steels such as 4140 and 4340.
If you look at the physical qualities that these precipitating hardenning Steels, (17-4), offer, you would figure that they would be ideal for the manufacture of Actions. They just about are. You can go through one simple agging proccess, (where the steel is brought to a specific temperature for a specific time, and then air cooled), that produces the desired properties. For instance, H1150 17-4 means the steel was heated for exactly 4 hours at 1150 degrees, and then air cooled. The 900 grade as mentioned by George is usually the highest strength level reached, but machinability and ductility do drop conciderably.
The 1050 grade gives a good combination of ductility, hardness, tensil, and yeild strength.
The drawbacks to the precipitating hardenning steels as opposed to regular alloy steels is initial material cost, and the fact that for high production work, they are pretty hard on tooling. However, some of the improvements in cutting tools, and machinery, in the past decades has negated some of this.
416 will make a perfectly good action, Remington has been using it (as the rumor says), for their Stainless Actions for years. I can't amagine anything being more abusive than a Ultra Mag with 100+ grns of powder packed in.
Of course, there is still the choice of 4140, or 4340. The advantages of these are initial lower material cost, ease in machining, and good physical properties. They do have to be heat treated, (final temper draw), before final machining, as they will warp and creep. And of course, they will rust.
Since 416R does give up some ductility, it would not be my first choice. It's superior machinability makes a lot of difference when trying to establish a small diameter precision hole in a 29 inch long barrel blank, but there are no such obsticles in the machining of an action.
It is no secret why custom action makers prefer 17-4 or similiar precipitating hardenning stainless steels for actions. They can purchase annealed and normalized bar stock that is just about to size, do all of the criticle machine work, then age harden it for the best combination of strength and ductility with little fear of creep or distortion. (some do heat treat before final machining) On top of that, it doesn't rust.
You did not say what you would use for the bolt. I believe that S-7 tool steel is the best choice, but 4140, and 4340, are not far behind. I say S-7 because it has unique properties that allow a high RC hardness, (for anti- galling qualities), high tensil and yeild strengths, while still maintaining a very high degree of ductility.
The drawback to S-7 is that the heat treat proccess MUST be adhered to in a strengent manner. There is very little tolerance in the temperature, or the time of heat.
A final note, what ever steel you choose, be sure to get as premium of a grade as is available. For instance, in 4140, and 4340, I would settle forno less than the "premium aircraft quality". These grades are manufactured with a typical VAR proccess that insures the cleanliness of the steel at the molecular level. This is VERY important when considering the important ductility factors.........jackie
