Why is no one using 416 Stainless Steel for a Monocore design.

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remmag1012
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Why is no one using 416 Stainless Steel for a Monocore design.

Post by remmag1012 » Wed Sep 20, 2017 9:45 am

I am new to Silencer Talk but I can not find an answer anywhere. I have made a couple silencers for a .22 LR and an AR-15 in 5.56. (Both Monocore designs) I am getting ready to make a monocore design for a 300 Win. Mag. Is there a reason that no one using 416 Stainless Steel to make a momocore baffle :? for a magnum rifle? :?

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Re: Why is no one using 416 Stainless Steel for a Monocore design.

Post by T-Rex » Wed Sep 20, 2017 10:18 am

I'm going to say it's because 416 doesn't offer the strength and resilience to erosion that other metals do. It cuts great, but, being that you can't easily replace baffles, you're better off using something that will last. 17-4PH SS is low cost and will provide substantial qualities needed for suppressor design & usage.
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Re: Why is no one using 416 Stainless Steel for a Monocore design.

Post by John A. » Wed Sep 20, 2017 10:20 am

^That's better than what I had.
I don't care what your chart says

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Re: Why is no one using 416 Stainless Steel for a Monocore design.

Post by speed6 » Wed Sep 20, 2017 12:37 pm

416 is "resufurized," meaning it is alloyed with extra sulfur to make it "free machining." The sulfur causes sulfur inclusions at grain boundaries (that's why it's easier to machine), and since sulfur has a lower melting point that the base metal, these will cause weak points in the grain structure at high temp. I.e. it is not as suitable for high-temp erosion resistance as other alloys. At least that is my understanding.

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Re: Why is no one using 416 Stainless Steel for a Monocore design.

Post by BinaryAndy » Wed Sep 20, 2017 11:42 pm

416 would be a great material for a suppressor. Good yield strength, decent abrasion resistance, easy to machine. That's what they make stainless barrels out of, and those don't wear out any faster than barrels made of 4140, which is also an excellent material for suppressors. 410, which is 416 without the sulfur, is slightly stronger and more wear resistant but more difficult to machine. 416 would be worlds better than 304 or 316, which is what everyone used before they "discovered" 17-4.

One minor point against 416 for a monocore or rear cap is that using the same alloy of stainless steel for both sides of a threaded connection makes galling more likely. So, if you thread it onto a stainless barrel, use antisieze or something.
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Re: Why is no one using 416 Stainless Steel for a Monocore design.

Post by T-Rex » Thu Sep 21, 2017 8:46 am

416 is suitable for barrel use mostly because the material is run parallel with the flow of gases (I have no issues w/ its strength). Once you start putting baffles in the way, the hot gases interact directly w/ the metal surface, causing pitting and depositing corrosive elements w/in. 416 does not play well with chlorides and is also not ideal for welding. Barrels wear out and need replacing, something average Joe can do. I'd go with 410, before 416, sacrificing a bit of machinability for greater corrosion resistance and much better welding characteristics.

After all this, let's face reality. Aluminum is used for centerfire rifle (even magnum) cartridges. If you're not a heavy shooter and don't abuse your equipment, most any metal can last a long time.

My specific point was, 17-4 is superior to 416 in almost every category, it might have less machinability but is, also, less costly. This would be my choice, unless, of course, I was getting it for free :wink: :lol:
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Re: Why is no one using 416 Stainless Steel for a Monocore design.

Post by BinaryAndy » Thu Sep 21, 2017 10:18 pm

Hot gasses interact directly with the throat area of a rifle barrel with a lot more heat and pressure than we see in a suppressor. I agree though, 17-4 is a better material for suppressors. It's also a better material for barrels, by the way. In both cases, 17-4 is more wear resistant and 416 is easier to machine. Machinability is, of course, of greater significance for a barrel than for a suppressor, so 416 is generally used for barrels and 17-4 for suppressors.

416 also needs to be heat treated to have a good yield strength, while 17-4 is pretty darn strong annealed and can optionally be heat treated to have an even better yield strength.

In a suppressor I sincerely doubt corrosion would be a problem with either material. I've made a few suppressors from 4140 with no surface treatment, and put quite a number of rounds through them for testing. They always rust on the outside long before I see any corrosion at all on the inside. I'll admit I don't fully understand why that is, but it leads me to believe that the inside of a suppressor is not a terribly corrosive environment (assuming you don't use any Soviet mil-surp ammo...).

TL;DR: Use 17-4 unless you get 416 for free.
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Re: Why is no one using 416 Stainless Steel for a Monocore design.

Post by Capt. Link. » Sat Sep 23, 2017 10:49 am

Been using 416 for suppressor baffles since the mid 1990s.Its a very good choice and the equal to many other metals once you harden it.The ease of machining on the typical hobby sized lathe is a blessing and hardening the material is not difficult in a backyard setup.
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Re: Why is no one using 416 Stainless Steel for a Monocore design.

Post by remmag1012 » Sat Dec 02, 2017 10:27 pm

Thank you very much for the information. I knew I came to the right place.

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Re: Why is no one using 416 Stainless Steel for a Monocore design.

Post by Rich V » Mon Dec 04, 2017 9:39 am

BinaryAndy wrote:Hot gasses interact directly with the throat area of a rifle barrel with a lot more heat and pressure than we see in a suppressor. I agree though, 17-4 is a better material for suppressors. It's also a better material for barrels, by the way. In both cases, 17-4 is more wear resistant and 416 is easier to machine. Machinability is, of course, of greater significance for a barrel than for a suppressor, so 416 is generally used for barrels and 17-4 for suppressors.

416 also needs to be heat treated to have a good yield strength, while 17-4 is pretty darn strong annealed and can optionally be heat treated to have an even better yield strength.

In a suppressor I sincerely doubt corrosion would be a problem with either material. I've made a few suppressors from 4140 with no surface treatment, and put quite a number of rounds through them for testing. They always rust on the outside long before I see any corrosion at all on the inside. I'll admit I don't fully understand why that is, but it leads me to believe that the inside of a suppressor is not a terribly corrosive environment (assuming you don't use any Soviet mil-surp ammo...).

TL;DR: Use 17-4 unless you get 416 for free.
Good post Andy.
A couple of comments. 17-4 SS is very strong in the annealed state - UTS = 150,000 psi. This is much stronger than the 300 series SS @~ 30,000 psi UTS. Unfortunately it is on the soft side @ Rc ~33 and will dent easily.

In the H900 condition17-4 hardness increases to Rc 43-45 range and is very dent resistant. In gaining extra hardness comes the benefit of greatly decreasing galling when using 17-4 for threaded parts. Galling with stainless on stainless is a big problem and can easily lock up threaded components irreversibly. I have had this happen with 17-4 annealed on 316 threads with just moderate tension applied in the absence of lubricants.

Your comment about 4140 not corroding inside a silencer is easy to explain. A major component of the exhaust gas from smokeless powder is ammonia. Compounds like ammonia and amines inhibit corrosion and are often the active components used for vapor anti-corrosion products. In effect you are producing a vapor anti-corrosion inhibitor with every shot you put threw a can. Since ammonia is very volatile it dissipates rapidly and will not protect the metal from long term corrosion. Shooting corrosive ammo deposits potassium/sodium salts that are very powerful corrosion promoters that do not evaporate like ammonia. Hence the corrosion seen when shooting this type of ammo.

In short- The reason for heat treating 17-4 is to gain hardness and less about gaining strength. (UTS for 17-4A = 150k psi vs 17-4H900 = 200k psi).

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