Anybody with a metallurgy background?

I was researching rifle barrels and came across something I hope someone with industry experience can clear up. 

Many rifle barrels are made from 416r stainless. I was talking with a barrel maker, that I have several rifles with his barrels,  and he stated he bought his stainless from Europe and it was Crucible steel that is no longer made here, or at least to his liking. I guess crucible steel is poured at a higher temp which allows a better mixing of the base materials?

What I think is the difference is that there is SS416, SS416r and then there is Crucible stainless in various formulas and then there is Crucible Steel Inc in New York. Crucible Steel Inc. made 416r for barrels but I don't think it was done in a crucible. I believe they went out of business until they were recently reorganized.

Is Crucible 416r is known to have different characteristics? Is it harder like a Damascus type?

Thanks for any insights.

I believe Crucible is only made by Crucible Specialty Metal Division

crucible steel is a foundry process. it's not only from one place. it was developed by Huntsman in the late 1700's.

As I understand it, Crucible has a “special grade” of 416R that is called “Gun barrel Quality” which is controlled for impurities and alloy segregation.  The “R” means it has been “resulphurized” to aid machining (which is important in making barrels).  It isn’t any harder or softer, generally, than other 416 steels.  Crucible was a “specialty” maker of steels for the Aerospace and Defense industries and gun barrel steels were a part of that. I believe that most of their products were melted from scrap steels in either Vacuum Arc furnaces or Electroslag furnaces.

416r is a grade code (like 17-5, 15-5 etc) that denotes the composition in terms of chemistry/element content (chrome, manganese, carbon, sulphur, etc.)

Crucible is the manufacturer, and they're still in business as far as I know. It's also produced by Penn Stainless, and many others.

416 grade has a high tolerance for heat, is easily machined, is designed to be quenched/hardened, has great corrosion resistant properties, as well as low friction which prevents seizing and galling.

In other words, it's ideal for rifle barrels.

As far as the grade (S41600) it can be made by any Steel maker, the chemical composition is a AISI standard.. but some mills (perhaps Crucible) have tighter tolerances and simply make a better product.

https://www.crucible.com/history.aspx


a quick read about Crucible the company, not the process.

Greetings,

A year ago, I telephoned Crucible asking to get some metallurgical data on the 416R barrels.

I did talk with, probably, the last employee in the USA technical division. We also had a nice talk about the demise of American Manufacturing.

He said most of the 416R steel is produced outside of the USA.

There are European datasheets that specifically address 416R. I cannot recall the European alloy numbers. Actually, there are several. DIN, UNS, Italian, etc.

416R originally came from the factory in three hardness levels ready to machine, ( HRC 24/28, 28/32, or 32/36).

It is possible to heat treat 416R to 40-45 HRC as used in Pistol Barrels.

It does machine very well and leaves a nice finish.

Cheers,

Dave

robert84010 wrote:Is Crucible 416r is known to have different characteristics? Is it harder like a Damascus type?

As I understand it, 416 steel is considered to be "gummy" when machined.  This means machined chips end up long and stringy, and do not break readily, resulting in a large mass on or very near the cutter.  In 416R, sulfur is added to 416 as a lubricant and a "chip breaker", making machining much easier.


NOTE:  There is a finite amount of sulfur which may be added to steel.  Add too much, and the risk of sulfur collecting at grain boundaries in the metal increases.  This leads in premature cracking of the barrel and subsequent failures.  Seem to recall that Crucible mentions "ultrasonically tested" in the comments for 416R, this is probably to ensure sulfur "stringers" do not exist in the steel they sell.  From the data sheet for 416R:

6) 100% ultrasonic testing for reliable barrels.

Hope this helps.

Hi Asa,
We machined a lot of 410 and 416 stainless where I used to work.
410 is the more difficult to machine without proper tooling/speeds/feeds.
416 is just 410 with sulfur added to produce "free machining" characteristics.
I was at a highpower match in OR and two positions away from me another shooter had an M1a barrel blowup due to sulfur strings.
Not a pleasant thing to happen, wood all over the line.

Wes Lorenz wrote:another shooter had an M1a barrel blowup due to sulfur strings.
Not a pleasant thing to happen, wood all over the line.

 I'd think likely some other 'organic' materials in his general vicinity as well.

The 'R' stands for 'Rifle Barrel Quality', as noted. Resulphurized is redundant.

There's more to machinability than hardness. Some years back, just for fun, I made up a couple blanks to thread. One was 416, the other S-7 tool steel. Both hardened and tempered to 45C. S-7 isn't made for that, took a bunch of steps in temp to get it down there. And no idea what the actual properties would be.

The difference in cutting 16TPI threads in them was amazing. The 416 peeled off beautiful shiny chips and left a gorgeous surface behind. Seemed to be no real strain on the machine or tooling. The S-7 ... Wow! I thought the insert was going to snap off at any moment. I could sense the load on the lathe as well. Finish was 'fair'. One of few tool steels that have any sort of material properties available, Tensile/Yield/Impact ... It's one of few that get used for anything other than tooling, landing gear for aircraft is one I think.

I fit up a barrel for a friend awhile back. Could not get the chamber reamer to cut. Called PTG about it, and he asked about the barrel. When I told him it had come from someone I thought was involved with the Palma team, he said 'oh, that's not 416, it's 410. Great barrels, last forever, but a bear to chamber'. He gave me some suggestions to try.

I wound up putting the reamer in a Morse ER chuck and driving the barrel by the muzzle and using the reamer as a 'center'. Brutal, but came out with a nice finish and the reamer in one piece.