Barrel Steels?

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varminter22

New member
I'm not a student of metallurgy. But when I read the following:

QUOTE
Chrome-Moly steel is generally not used for barrels due to several factors. Its tough to machine, its hard on the tooling used to machine it (end mills, face mills, lathe bits,etc.) and in some of its formulations it can have a problem with stress risers which lead to cracking and splitting due to fatigue.
Some Chrome Moly alloys like 4340 are used for barrels, but commonly stainless steels like 4140, 416 and 416R, are used. These Stainless Steel barrels are generally not produced for the really hot magnum cartridges. Also the barrels made of 416 and 416R usually come with some warning about using them in extremely low temperatures, as they become a bit brittle below 0 degrees F. and may burst when fired.
UNQUOTE

I wondered about the accuracy of the statement(s).

I thought stainless steel was harder on tooling than chromoly steel.
 
Well then I guess you'd better BECOME a student of metallurgy if you're gonna' question folks veracity.........


First of all you don't list your cite-

Secondly you don't specify which statement(s) you have a problem with-

and,THIRDly "I thought stainless steel was harder on tooling than chromoly steel" hardly qualifies as a rebuttal of opinion with facts............

What are you asking or saying????? WHICH "chromoly" and WHICH "stainless" are you saying are harder on tooling than the other? As worded, your post is suspiciously like saying "I've heard that Fords are faster than Chevy's".........please elaborate.

al
 
I'm too lazy to go look up a reference, but I believe that 4140 is a chrome-moly steel. Since various commercial rifle makers have used chrome-moly steel of one variety or the other for barrels and actions since at least the 1950's I wonder what your source is. Yes I'm old enough to remember the ads in shooting magazines back in the '50's extolling the strength and virtues of their chrome-moly barrels.

Machinability of steels is beyond my pay grade.
 
Chromoly steel is stronger and will withstand greater pressures than stainless. That is the reason pressure vessels are not made from stainless steel. As for machinability, it depends on the grade. Another good example is the bolts used in steel structures. Bridges for instance. Always carbon steel.
 
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varminter22 said:
I'm not a student of metallurgy.
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I was. There are other metallurgists on this board as well.

Chrome-Moly steel is generally not used for barrels due to several factors. Its tough to machine, its hard on the tooling used to machine it (end mills, face mills, lathe bits,etc.) and in some of its formulations it can have a problem with stress risers which lead to cracking and splitting due to fatigue.
Some Chrome Moly alloys like 4340 are used for barrels...
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Actually, lots of rifle barrels today are made from chrome-moly steel - especially factory barrels. It can be formed by various methods, and sometimes is easier to obtain than rifle barrel grade stainless steels. Being able to crank out lots of barrels at reasonable costs is a good thing.

Stainless is used for most competition barrels today because many of the grades used do machine better, and/or the finish on the completed product is better (smoother) than if using chrome-moly. For example, 416R has sulfur added to the alloy to promote machining. (Not a machinist, but think the sulfur helps the chips break up - can anyone confirm or deny this?)

These Stainless Steel barrels are generally not produced for the really hot magnum cartridges.
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Not true. Quite a few magnum rifle barrels are made in stainless - including Remington Ultramagnums and .338 Lapuas.

Also the barrels made of 416 and 416R usually come with some warning about using them in extremely low temperatures, as they become a bit brittle below 0 degrees F. and may burst when fired.
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True, and partially true. 416/416R can become brittle when the temperature changes. When this happens (could be anywhere between 70*F and -40*F) depends on a number of factors, including alloy composition. Concentration and location of sulfur and phosphorus concentrations can promote cracking. These same factors may also raise the temperature at which failures occur: add more of either one, and "ductile to brittle transition temperature" occurs at warmer temperatures.

Google "ductile to brittle transition temperature" and "steel" sometime, and you'll get a small library of related topics (I got 18,000+ topics when trying it a few moments ago). Much of this material is written for graduate student or higher level educations (I get lost in the math or most of the papers), but some is good, basic material. Such as http://www.matsci.ucdavis.edu/MatSciLT/EMS-174L/Files/DuctileBrittleTransition.pdf. This is an intro level materials science lab project, but gives good background material on DBTT.

Hope this helps.

Asa
 
Sulfur added to the steel acts more on the molecular level than an actual physical chip breaker allthough it may help chip breaking also.
The molecular bonds of the sulfur are weaker than the other elements in the steel. So they allow the steel to shear more easily.
A very small ammount of sulfur can have a good effect on machineability but have a small effect on tensile strength.
So it is practical only to a point for certain suitable purposes .
The problem is getting the sulfur content uniformly through the steel section(Melt).
4140 is not hard to machine in its non hardened state .
4340 would be harder to machine I feel than 4140 as its supplied in a harder state than 4140 and has higher tensile and yeild strength.
Also it has 1.8% nickel content which could affect bluing color to a slight red tinge.
Thats not to say that it could not be used for a barrel.
 
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Thanks, guys. Good info.

I wasn't calling the poster a "liar" or anything of the sort. His statements just didn't jive with what I've read and heard.

As usual, the knowledge base here is wonderful.
 
Noap no sir !

RStiefel said:
Chromoly steel is stronger and will withstand greater pressures than stainless. That is the reason pressure vessels are not made from stainless steel. As for machinability, it depends on the grade. Another good example is the bolts used in steel structures. Bridges for instance. Always mild steel.
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I'm an Iron Worker by trade. Only time mild steel bolts are used is for temporary erection aids.( Erect the beam,then weld it) Those Bolts in my business are known Machine bolts ( Mild steel) with the #307 . Now the permanent bolt we use are know as" High strength" bolts are designated 325s and 490s. An engineer once explained the difference. He mentioned that a Modern day Nuclear submarine's hull is made with grade 100 steel. 307s are grade 50 steel just as most of the steel beams and girders and columns . But 325 bolts are grade 90 and 490 are grade 120. If to much torque is applied they'll snap . But just the right amount and they'll last and last and last.
 
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Worker is correct. I am a structural engineer, and I would never use A307 bolts for beam, girder, or column connections. We use A307 bolts for purlins, girts, or anchor bolts. Others are A325 (hardly ever use A490 bolts). The high strength bolts also come in X for threads excluded from the conneted parts or N for included. There are also bearing connectinos where the bolts do not have to be tensioned and slip critical connections where they do. By the way, the A### is shorthand for an ASTM specification, i.e. ASTM A325X.
 
Specific Steels for Specific Applications

Probably 98 percent of the population look at steel in two ways. If it rust, it is regular Steel, if it is shiney and will not rust, it is Stainless Steel.

Of course, there are multitudes of different grades of every category of "steel". Many steels appear to be virtually identicle at first glance, but will have trace elements added to the alloy content to enhance a specific property. A glance at a typical steel supply book that list all ASTM numbers willshow that manufacturers are constanly playing with different alloying agents to get a specific property that might make a certain alloy steel more usefull in a specific inviroment.

Stainless steels, in the simplist terms, can be divided into three categories. Those that respond to a standard heat treat, (due to varying carbon content), such as hardenning and tempering, (the "400 series" such as 410, thru 440 are good examples), those that respond to a "age hardenning" proccess, such as the precipitating Hardenning Stainless Steels, (17-4, 15-5, l-50), and those that have a minimum carbon content and get their properties soley from alloy content, (304, 308, 316, are examples).

416R Barrel Steel is in the first category, it reponds to what we call a standard hardenning and tempering proccess to obtain certain properties. As has been noted, the primary reason for it's popularity in the barrel industry is it does poccess a free machining quality combined with a "adequate" strength level for the intended purpose.

The most common chrome moly steel used for barrels is 4140, or something pretty close. In most cases, the heat treat is in the low to mid 30's RC, this gives excellent strength while still allowing for a reasonable machining capability.

I personally do not think one is any better than the other. Most barrel makers will tell you that the main reason for using 416R in premium match barrels is because it is much easier to establish the ID to the tolerances that are demanded in this class of barrel. In short, it makes life easier.

That is not to say that you can't do the same in Chrome Moly. It is just for the mass produced premium barrels, 416R has seemed to become the steel of choice.

There are other steels. Lothar Walthar uses a precipitating hardnenning stainless that they call L-50. I suspect it is quite similiar to either 17-4 or 15-5 PH. I have no idea what the Stainless Alloy that manufacturers such as Ruger use, but the machinability can best be descibed as "astrocious".

The thing about stainless loosing ductility at lower temperatures is referring to 416. And this is particularilly when used in thin cross sections, such as a light weight barrel chambered in a big diameter case such as a Ultra Mag. For these applications, if you still want a Stainless barrel, manufactures such as Krieger recommend using 410, which does not have the free machining quality that 416R exibits, and does have a better ductility factor..

Actually, 416R was specifically designed for the manufacture of precision Rifle Barrels. But the exact same alloy can be seen in catalogues under the heading, "precision pump shaft material".......jackie
 
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Rarely used

Mountain Mike said:
Worker is correct. I am a structural engineer, and I would never use A307 bolts for beam, girder, or column connections. We use A307 bolts for purlins, girts, or anchor bolts. Others are A325 (hardly ever use A490 bolts). The high strength bolts also come in X for threads excluded from the conneted parts or N for included. There are also bearing connectinos where the bolts do not have to be tensioned and slip critical connections where they do. By the way, the A### is shorthand for an ASTM specification, i.e. ASTM A325X.
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Mountain man every once in a while we'll use A490s. For instance here in the SF Bay area were building a new Bay bridge and we used a A490 bolt that required 3 3/8 socket we torque them with 3700 FT Lbs. A Cal trans inspector was breathing down our backs for every single LB of torque.
 
Jackie

can the CM barrels be lapped to the same degree of smoothness as say 416R?
 
????

I am not in the barrel making business, but from a machinist point of view, I would say that there would be very little difference in the dgree of finish that lapping would produce in either.

Maybe one of the pro barrel builders will chime in on this........jackie
 
jackie schmidt said:
The thing about stainless loosing ductility at lower temperatures is referring to 416. And this is particularilly when used in thin cross sections, such as a light weight barrel chambered in a big diameter case such as a Ultra Mag. For these applications, if you still want a Stainless barrel, manufactures such as Krieger recommend using 410, which does not have the free machining quality that 416R exibits, and does have a better ductility factor..
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Sorry Jackie, two points above are not correct.

1. AFAIK, nearly all 400 series stainless loses ductility as temperature falls. The question is when, not if. 410 has a lower transition temperature than 416, but it too will exhibit an abrupt loss of strength when temperature falls into the correct range. Chrome-moly steels also exhibit such behavior, but (depending on the alloy) transition temperatures can be lower than with 410 or 416.

2. While high pressure cases can cause failures, 416R barrels have failed in rifles chambered in .243 Winchester, and even in .308 Winchester. The latter was a target rifle barrel, with OD at the failure initiation point of over .800". When cracks grow over a critical size, failure occurs. IIRC, critical crack size (radius) can be independent of thickness.

Asa
 
Yam

You are correct. I said 416 because that is what the vast majority of Stainless Steel Barrels manufactured by Krieger, Shilen, Hart, and other custom manufacturers are made from.........jackie
 
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Whats your thoughts on Lothar Walther barrels, they claim a LW50 SS to replace and improve upon 416R. I've heard some gunsmiths don't want to work with these barrels as they are hard on cutting dies.
 
Haze10

Lothar Walthar says that the alloy that is used in the L50 Barrels is proprietary. But as I stated befor, it is some sort of Precipitating Hardenning Stainless, much like 15-5 or 17-4.

All you have to do is go to their web site and take a look at their chambering recomendations, and you will see that yes, it is quite hard on tooling when compared to 416R, or even 4140 at the hardness level used by most barrel manufacturers. Plus, they talk about having to "polish" the throat and lead to avoid excessive fouling, I guess this is because "gunsmiths" aren't skilled enough to ream a smooth enough chamber..

Seen anybody winning in 100-200 yard Benchrest with one??

Since the "advantages" that are touted by using this steel are a non issue in Benchrest, most Gunsmiths simply say, "why bother".

Keep in mind, many Benchrest Gunsmith's operations are rather small, some boardering on "garage" status. They use a minimum amount of high quality equipment, (combined with high skill), to accomplish a very specific task. I would bet that many of their eyes just glaze over when they read that recomended procedure on the Lothar site.

But Lothar is correct. A barrel made from that alloy, (if indeed it is a PH Stainless), will not suffer from the same maladys as does the 400 series. In fact, most PH Stainless Steels are known for their superior impact properties, (ductility), combined with good tensil and yeild strength.

If I were to build a big super boomer for hunting, or perhaps a hot burning live varmint Rifle, a Lothar barrel would be a good choice. But I am not going to mess with one for Competition........jackie
 
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