It is my understanding that there are three types of stainless used for most custom actions. They are 15-5, 17-4PH , and 416R. I know that the 416 machines very well, but aren't the other types more suited to use in actions? I am just seeking information, not bashing anyone's actions. Thanks, James Mock
What is the preferred stainless steel for custom actions?
- Thread starter JDMock
- Start date
RTillery
New member
James, I have built a couple of actions on 17-4 and had them nitrided by a friend with a crankshaft shop. They have worked well and have put thousands of rounds down range. That said, I am considering buying a new "store bought" action and I would like someone to talk about the difference/advantages between a stainless action, and a chrome-moly action. Any info on Melonited treatment would be also appreciated. TIA, Roger
Mike Bryant
Active member
I like the chrome moly actions as well. It seems the longer you shoot them the slicker they get and don't seem to have the galling problems that stainless action can have.
Bill Gammon
New member
I have had my Swindlehurst Stainless Steel Action since 1986 and it has never galled yet, of course I do not win much. But I am mystify by your statement? Keep it lubed and it works, keep any action lubed and it works. This is "NOT" a put down in any sense of the word, just a difference of opinion.
Bill
jackie schmidt
New member
The basic difference between 17-4 and 15-5 is 17-4 has a couple of percentages points more of Chromium, and and a few less percentage points of Nickel. In most general applications, there is very little difference in the properties of either. Both are Precipitation Hardenning Stainless Steels, in other words, they are heat treated to a certain strength level by one heat at a very specific temperature for a very specific amount of time.
15-5 is considered the more "modern of the two, but only by a few decades. 17-4 is believed to have a slight advantage in corrosion resistance, while 15-5 poccesses a slight advantage in ductility throughout the different strength levels.
Flip a coin.
416R is an entirely different animal. 416 is a martensitic steel, meaning it responds to a more conventional heat treating process in order to obtain a certain strength and hardness level., that being first hardening, and then tempering.
416R is a proprietary product of Crucible Steel that was developed specifically for rifle barrels, where they basically cut the sulphur to add strength levels as measured by ductility, but still retaining a fair amount of machinability.
If you order true 416R, you are supposed to be getting a steel that is manufactured by one of the processes such as VAR to insure the cleanliness of the steel at the molecular level. That being said, just like a lot of things in today's world, counterfeits are out there.
If measured by most impact strength test, 416 falls quite short of 17-4 and 15-5 in ductility, or impact strength. But it certainly has adequate amounts of these properties for applications such as a Rifle Action, while offering a great advantage in machinability.
This is just my opinion, but some of the finest actions ever built that combined the best properties were the older cast 17-4 actions produced by Farley. He used the lost wax/ceramic mold method of casting. This material, coupled with a bolt made from S-7 tool steel at 45 RC hardness made a great combination for stiffness, anti-gall properties, and overall strength for an action in the 32 ounce weight range used in most Benchrest Actions.
The two Rifle I shoot now in Competition are older Farleys, both around 1997 vintage. After thousands, and thousands of rounds at Benchrest pressures, neither has shown any signs of galling, or wear.
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James A. Kelbly
New member
Here at Kelbly's we use 416RS and when bolts and action body are at correct hardness, there is no galling. We are Nitride Hard coating a lot of actions and this makes the slickest action you can buy.
Jim
Jim
416 vs 17/4
Like Jackie stated, 17/4 and 15/5 are almost identical. I have actually talked to mills that make the material, and if they shoot for the middle, tolerances on the content allow them to use it for both. The 15/5 was put off as being a better steel. The biggest contributor to that statement is that most 15/5 is VAR steel versus maybe/maybe not on the 17/4. I have used both in actions and am not a big fan of them.
The advantage of 17/4 and 15/5 is stability during heat treat. They only go to 950 deg F or so and don't warp at all if using good stress relieved steel. 416, 416R etc has to be taken up to near 1900 deg and then quenched and tempered back. IF you use a good stress relieved steel and a good heat treater, you can keep the warpage to a few thousands on an action body. We machine all the lugs, faces and threads after heat treat to eliminate the issues on those surfaces. We also wire edm the raceways after to keep them straight.
The disadvantage of 17/4 and 15/5 is the extreme galling properties. Although it has great toughness and ductility, it is most likely the worst of the stainless steels for galling. Even when using 4140 bolts against it, it can gall very easily. Nitriding the 17/4 and 15/5 helps that a lot. I much prefer 416 types of steel due to this and the machinability. I use a 416R version, the R stands for reduced sulfur. I only use VAR, stress relieved barrel quality steel for our actions. They are heat treated to 700 deg F. On the 416 steels there is a no mans land for the heat treat condition. Ductility goes way down in the 750 to 1000 deg range for tempering. The matrix is somewhat unstable in that region. It has to do with how the carbon migrates from one crystal structure to the other. Anyone interested can google it. In my defense days, we would use lots of 416 steel, but were not allowed to use it in this region. At 700 deg the hardness is about Rc40-42. At 1000 deg is goes down to about Rc31. In my opinion there is no reason to temper above 700 deg F and lots of reasons not to in the centerfire action market. The ductility, charpy notch and elongation numbers all go down until you get past the zone. At 700 you still get the hardness and keep the ductility you need.
I am a big fan of the nitriding on lots of parts. We use the melonite process at MMI Arkansas for many of our parts. We nitride our 4140 bolts at a lower temperature (950 deg F) so the core stays hard. We nitride our rimfire action bodies at the same temps, this is one area I don't mind hitting the mid temp range no mans land. Although the ductility goes down, a rimfire action has such low stresses that there will never be a stress fracture issue. The surface hardness and slickness makes up for it. I will not nitride our centerfire actions though. I don't like the material properties in the 950 deg range and if run at 1000 deg or more, the core gets too soft and we see lug setback etc. I am not willing to take the risk on it. MMI has strict instructions to never process our centerfire actions even if a customer sends them in. All of our black colored centerfire actions are black oxide processed at about 250 deg F.
That's more than you probably ever wanted to know about steels, but there it is anyway.
Like Jackie stated, 17/4 and 15/5 are almost identical. I have actually talked to mills that make the material, and if they shoot for the middle, tolerances on the content allow them to use it for both. The 15/5 was put off as being a better steel. The biggest contributor to that statement is that most 15/5 is VAR steel versus maybe/maybe not on the 17/4. I have used both in actions and am not a big fan of them.
The advantage of 17/4 and 15/5 is stability during heat treat. They only go to 950 deg F or so and don't warp at all if using good stress relieved steel. 416, 416R etc has to be taken up to near 1900 deg and then quenched and tempered back. IF you use a good stress relieved steel and a good heat treater, you can keep the warpage to a few thousands on an action body. We machine all the lugs, faces and threads after heat treat to eliminate the issues on those surfaces. We also wire edm the raceways after to keep them straight.
The disadvantage of 17/4 and 15/5 is the extreme galling properties. Although it has great toughness and ductility, it is most likely the worst of the stainless steels for galling. Even when using 4140 bolts against it, it can gall very easily. Nitriding the 17/4 and 15/5 helps that a lot. I much prefer 416 types of steel due to this and the machinability. I use a 416R version, the R stands for reduced sulfur. I only use VAR, stress relieved barrel quality steel for our actions. They are heat treated to 700 deg F. On the 416 steels there is a no mans land for the heat treat condition. Ductility goes way down in the 750 to 1000 deg range for tempering. The matrix is somewhat unstable in that region. It has to do with how the carbon migrates from one crystal structure to the other. Anyone interested can google it. In my defense days, we would use lots of 416 steel, but were not allowed to use it in this region. At 700 deg the hardness is about Rc40-42. At 1000 deg is goes down to about Rc31. In my opinion there is no reason to temper above 700 deg F and lots of reasons not to in the centerfire action market. The ductility, charpy notch and elongation numbers all go down until you get past the zone. At 700 you still get the hardness and keep the ductility you need.
I am a big fan of the nitriding on lots of parts. We use the melonite process at MMI Arkansas for many of our parts. We nitride our 4140 bolts at a lower temperature (950 deg F) so the core stays hard. We nitride our rimfire action bodies at the same temps, this is one area I don't mind hitting the mid temp range no mans land. Although the ductility goes down, a rimfire action has such low stresses that there will never be a stress fracture issue. The surface hardness and slickness makes up for it. I will not nitride our centerfire actions though. I don't like the material properties in the 950 deg range and if run at 1000 deg or more, the core gets too soft and we see lug setback etc. I am not willing to take the risk on it. MMI has strict instructions to never process our centerfire actions even if a customer sends them in. All of our black colored centerfire actions are black oxide processed at about 250 deg F.
That's more than you probably ever wanted to know about steels, but there it is anyway.
jackie schmidt
New member
By the way, on my Rail Gun, I use a drop port Stiller Diamondback, which as Jerry noted is machine from 416R, and it operates flawlessly.
Boyd Allen
Active member
Jerry, and the others,
Thanks for the education.
Thanks for the education.
Mike Bryant
Active member
Keep them clean, keep them lubed and you won't have any problems with galling whether it's stainless or chrome moly. In dirty conditions like what you commonly get at Phoenix or Midland where it's hard to keep it clean, I think is where you will have trouble with galling lugs. Galling just seems more common in stainless actions especially those made of 17-4 than chrome moly. However, chrome moly will rust. If I lived where Jackie lives in Houston, I'd probably have a different opinion about chrome moly actions.
JerrySharrett
Senile Member
Chrome moly (chrome molybdenum) is a carbon steel and has considerably more carbon (graphite)mtha any of the stainless steel families...but rusts much more freely.
Greg Thannel used to keep one lathe set up just to remachine galled stainless action threads.
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Greg Thannel used to keep one lathe set up just to remachine galled stainless action threads.
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