Please advise SS material for barrel nut

A

alinwa

oft dis'd member
I've been experimenting with barrel nuts.

Most of them I've made from grade 8 nuts, the few SS I've made have been from cut offs of 1.450 Shilen and Krieger railgun barrels. I have no idea how hard these are, I've just been slobbering them with the late Davey Dohrrmannnnn's (Miss You Man :( ) white owlpoo and tightening them as much as I dare......but SS on SS at similar Brinnell always sets my hair on edge. GALLS me you might say....

I just ordered a couple TAC338's which have 1.450 diameter.

Can some of you smart people opine re a stainless alloy which is harder/tuffer/hardenable so that I can make it harder than barrel steel? The only other option I can come up with is having my nuts melonited, but I'd rather not.
 
The Barrel steel will be in the RC 22 to 28 range. 416 can easily be heat treated to about RC 40 and might be viable in that range, maybe a little less. A lot of different stainless alloys are used for threaded fasteners, but 416 is a pretty good choice for cut threads. Other alloys (300 series) are usually used for formed threads as the forming process work hardens the material. Of course the best option would be to use 4340 at RC 36 or so and treat it by Melanite, hard chrome, or nickel.
 
SGS said:
The Barrel steel will be in the RC 22 to 28 range. 416 can easily be heat treated to about RC 40 and might be viable in that range, maybe a little less. A lot of different stainless alloys are used for threaded fasteners, but 416 is a pretty good choice for cut threads. Other alloys (300 series) are usually used for formed threads as the forming process work hardens the material. Of course the best option would be to use 4340 at RC 36 or so and treat it by Melanite, hard chrome, or nickel.
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OK SGS, I'm really ignorant here.....I just go down to Metal Supermarkets and ask for metal by number at the direction of guys like you.......

You say "The Barrel steel will be in the RC 22 to 28 range. 416 can easily be heat treated to about RC 40 and might be viable in that range," does this mean that barrel steel is 416? I've seen designations including 416, 416R and 416RS but I don't know if that's a standard...

And that it can be easily hardened? I've always "heard" that SS barrels "don't harden in the throat" (air harden?)

If so, HOW? Heat and water quench?.....Draw back?

I do have both 4340 and 12L14 in my steel pile and have hardened them but I'm hoping for a stainless option.
 
alinwa said:
Are you going to harden them?
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No I didn't think there would be a need to although i could .
17-4 seems tough and I didn't think I would want it to be to hard as it would be supporting the barrel were the chaimber is , giving added strength.
What do you think?
Something I have been thinking about last couple days.
 
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17-4 would start out at about Rc35 I think but not sure how good it would be at lower Temps.
Don't think I would be draging this one out at ten below but you never know
 
cloudrepair said:
No I didn't think there would be a need to although i could .
17-4 seems tough and I didn't think I would want it to be to hard as it would be supporting the barrel were the chaimber is , giving added strength.
What do you think?
Something I have been thinking about last couple days.
Click to expand...

My goal is simply to avoid galling. I've had some bad experiences with stainless on stainless.

Regarding the added strength, no, I don't consider this to be an issue. IMO the only place the threads have any effect at all is a small section including only the first two threads of the action and the first two threads of the nut, generally separated by a (thick, in my case) recoil lug. It is my opinion that the threads at the "front" or muzzle end of the nut aren't even touching the barrel except incidentally, and that the "rear" or action end of the barrel is similarly hanging in space.

I've touched on tapered tenon threads but not pursued the concept.
 
If you use 17-4, you really need to use it in H1150 grade. If you use it in "condition A", you are opening the door to a galled thread.

Without getting too technical, Stainless Steels are generally divided into three types, Austenitic, Martinsitic, and Precipitation Hardenning.

Austenitic includes the most of the 300 series, which do not respond to heat treating. Martinsitic Stainless includes most of the 400 series, which do respond to a hardenning and tempering, much like alloy steels. Precipitation Hardenning steels include, 17-4, 15-5, and a host of others. They are heat treated for strength and hardness by a single heat for a specific time at a specific temperature.

If you are not going to use a Precipitation Hardenning Stainless at H1150, use a piece of 4140 or 4340 at around 34-36RC hardness.

Or, get on line and order a Grade 8 bolt in about 1 1/2" diameter and use it as your material. That is always a good source for a piece of high strength alloy steel.
 
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cloudrepair said:
17-4 would start out at about Rc35 I think but not sure how good it would be at lower Temps.
Don't think I would be draging this one out at ten below but you never know
Click to expand...

I'm not concerned w/temps as ruptures don't involve the chambered tenon section of the rifle barrel. Barrels pop from being machined too thin and typically with added built-in stress-concentrators on the flutes.
 
jackie schmidt said:
If you use 17-4, you really need to use it in H1150 grade. If you use it in "condition A", you are opening the door to a galled thread.

Without getting too technical, Stainless Steels are generally divided into three types, Austenitic, Martinsitic, and Precipitation Hardenning.

Austenitic includes the most of the 300 series, which do not respond to heat treating. Martinsitic Stainless includes most of the 400 series, which do respond to a hardenning and tempering, much like alloy steels. Precipitation Hardenning steels include, 17-4, 15-5, and a host of others. They are heat treated for strength and hardness by a single heat for a specific time at a specific temperature.

If you are not going to use a Precipitation Hardenning Stainless at H1150, use a piece of 4140 or 4340 at around 34-36RC hardness.

Or, get on line and order a Grade 8 bolt in about 1 1/2" diameter and use it as your material. That is always a good source for a piece of high strength alloy steel.
Click to expand...

OK Jackie......

Wheww.....

I'm still working my way thru this info. Going to take me some internet searching and reading my machining books to sort out what you've said.
 
jackie schmidt said:
If you use 17-4, you really need to use it in H1150 grade. If you use it in "condition A", you are opening the door to a galled thread.

Without getting too technical, Stainless Steels are generally divided into three types, Austenitic, Martinsitic, and Precipitation Hardenning.

Austenitic includes the most of the 300 series, which do not respond to heat treating. Martinsitic Stainless includes most of the 400 series, which do respond to a hardenning and tempering, much like alloy steels. Precipitation Hardenning steels include, 17-4, 15-5, and a host of others. They are heat treated for strength and hardness by a single heat for a specific time at a specific temperature.

If you are not going to use a Precipitation Hardenning Stainless at H1150, use a piece of 4140 or 4340 at around 34-36RC hardness.

Or, get on line and order a Grade 8 bolt in about 1 1/2" diameter and use it as your material. That is always a good source for a piece of high strength alloy steel.
Click to expand...
So if I had my 17-4 heat treated to say 25-35 RC it would be OK ,or just use a piece of 4140
Would I need to heat treat one made out of 416 stainless?
 
There is no reason to go overboard with hardness or material specs. 17-4PH SS at condition 1025 is about RC 38 and machines nicely. 416 SS also machines well and can be heat-treated to similar hardness. There is no reason to use anything else in the SS spectrum. Definitely do not use 316 or 304 SS as they have a tendency to gall and work harden. In a barrel nut at 100 ft-# torque, stress on the nut is low, enough hardness to prevent wrench deformation is really all that is required.

RWO
 
cloudrepair said:
Or what do you think of 304 for a barrel nut
Jackie?
I don't like working with it but?
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304 would not be my first choice. It does not have the physical properties of a true alloy steel, and tends to gall. It has it's place, just not for a nut that is subjected to a rather high load in a rather thin cross section.

The lure of any stainless is it matches a stainless barrel cosmetically and will not rust. So if you are going to use a stainless, at least use one that is suitable strength wise.
 
alinwa said:
OK SGS, I'm really ignorant here.....I just go down to Metal Supermarkets and ask for metal by number at the direction of guys like you.......

You say "The Barrel steel will be in the RC 22 to 28 range. 416 can easily be heat treated to about RC 40 and might be viable in that range," does this mean that barrel steel is 416? I've seen designations including 416, 416R and 416RS but I don't know if that's a standard...

And that it can be easily hardened? I've always "heard" that SS barrels "don't harden in the throat" (air harden?)

If so, HOW? Heat and water quench?.....Draw back?

I do have both 4340 and 12L14 in my steel pile and have hardened them but I'm hoping for a stainless option.
Click to expand...

I did mean that stainless barrel steel is 416. It is hardened by heating to 1600 to 2000 degrees and oil quench. Then draw to desired hardness. I have not attempted to treat any stainless myself. The facility I work in does it all using a variety of fancy ovens with inert gas or vacuum to avoid oxygen contamination. I would try to find a source for stock the size you want and heat treated to your specs. I agree with Jackie and RWO; either 17-4 or 416 in the RC 36 range. If you want to just use barrel scrap and you don't like the color of Melanite treatment, it can be bead blasted or polished so that the black is gone and still have a thin layer of very hard surface.

What size stock do you need? I might have something laying around in 17-4.
 
SGS said:
I did mean that stainless barrel steel is 416. It is hardened by heating to 1600 to 2000 degrees and oil quench. Then draw to desired hardness. I have not attempted to treat any stainless myself. The facility I work in does it all using a variety of fancy ovens with inert gas or vacuum to avoid oxygen contamination. I would try to find a source for stock the size you want and heat treated to your specs. I agree with Jackie and RWO; either 17-4 or 416 in the RC 36 range. If you want to just use barrel scrap and you don't like the color of Melanite treatment, it can be bead blasted or polished so that the black is gone and still have a thin layer of very hard surface.

What size stock do you need? I might have something laying around in 17-4.
Click to expand...

OK.... the reason for not wanting to melonite is simply the wait time/down time/ shipping hassle. Buying my stock pre-hardened as you suggest suits me fine :)

I'm looking for 1.5" round stock for making 1.450 nuts.
 
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