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Thread: 4140 barrel accuracy

  1. #11
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    Quote Originally Posted by JediGuy View Post
    Thanks for the clarification from everyone, and I didn’t word my question well.

    If I can follow on, my understanding has been that a stainless (416/416R) option will “maintain precision longer” but drop off faster once useful barrel life comes to an end, whereas 4150 will demonstrate a more gradual degradation in accuracy over the life of the barrel. Please correct me if that is wrong. In that context, with equal finishing from the manufacturer assumed, my question would be if 4140 would demonstrate behavior closer to stainless or 4150. My assumption is 4150, but this is the root of my question.
    Stainless will not maintain precision longer. 4140 will last longer than stainless in every way unless you let it corrode, 4150 will last longer than 4140 in every way. Melonite/nitrided 4140 or 4150 will last longer than raw 4140, 4150 or stainless.
    There are different grades of stainless, even different grades of 416/416R. Some barrels labeled 416R are unbelievably soft, Shilen comes to mind, they break in fast and wear out fast.
    I believe Noveske used a different grade that was harder which should last longer. If you talk to Steve at Criterion he'll tell you buttons pull better through 410. 410 is similar to LW50 although no one at Lothar will really say what LW50 is but both 410 and LW50 have better abrasive resistance and should last longer than the average 416R. Most stainless runs 28-32 Rockwell C.

    IMO the reasons smiths use stainless is because it's softer, easier to machine, quicker to cut, easier to lap, corrosion resistant and when they are done they are done, it is easier and quicker for most smiths to chamber and fit a barrel. They don't have to finish it by parkerizing or chroming or Melonite treating. Unless it is a true match grade barrel, Krieger, Bartlein, Lilja, Hart, PacNor etc there is really no benefit to buying it.
    Last edited by constructor; 03-13-23 at 18:25.

  2. #12
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    SS is much easier to work and finish than other grades which is why they are used for match/precision barrels.
    Almost a shame that all that careful work is blasted away with a shorter barrel life, well some anyway.

  3. #13
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    Great info, thanks for the explanation, @constructor

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    I never put much thought into a 4140. I assembled a 350 legend for my Dad with a CMMG thats 4140 and at 100 yards with hand loads its shooting a 2 inch 10 shot group.

    Changed my attitude towards 4140 a little.

  5. #15
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    I’ve read a whole bunch of different theories on 4140 vs. 4150 steel for barrels. The research I was doing was because I’ve been wanting to buy the FN M16A4. One of the draw backs I’ve been reading has been the 4140 barrel steel they use.

    My understanding is that it really isn’t a concern unless you’re doin FA shooting all the time. Honestly, I don’t know enough about the different steels to make an educated decision. I don’t own FA lowers, so maybe the 4140 won’t really matter.

    Edited to add: I haven’t read anything in regards to poor accuracy in that particular rifle using 4140 steel.

    Quote Originally Posted by JediGuy View Post
    I understand the mil standard 4150…. is the better steel for durability.

    But with the lower carbon content, does 4140 have relatively positive accuracy potential in any way similar to 416?
    Last edited by davidjinks; 03-26-23 at 14:56.

  6. #16
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    Quote Originally Posted by constructor View Post
    . . . .4150 will last longer than 4140 . . .
    Given that the difference between 4140 and 4150 is all of 0.10% carbon (or about 0.0000625 ounces, in your average barrel), just exactly how much longer will it last?

    A bar of normalized 4140 has the following properties:

    Hardness - HB 302 / RHb 99 / RHc 32 / HV 319
    Ultimate Tensile - 148 ksi
    Yield Tensile - 95 ksi
    Elongation - 17.7%
    Reduction - 46.8%
    Mod of Elasticity - 29,700 ksi
    Bulk Modulus - 23,200 ksi
    Poissons Ratio - 0.29
    Shear Modulus - 11,600 ksi

    A bar of normalized 4150 has the following properties:

    Hardness - HB 321 / RHb 99 / RHc 35 / HV 339
    Ultimate Tensile - 168 ksi
    Yield Tensile - 107 ksi
    Elongation - 11.7%
    Reduction - 31%
    Mod of Elasticity - 29,700 ksi
    Bulk Modulus - 23,200 ksi
    Poissons Ratio - 0.29
    Shear Modulus - 11,600 ksi

    The first thing someone will shout is that 4150 is 20 ksi stronger, but in this case the yield strength is more important. While you don't want blow apart (ultimate failure), you don't want it to bend or bulge, so the practical difference in the strength is only 12 ksi. So we can make a smaller barrel, Right? For a 70,000 psi proof load, the barrel can be all of 0.086" smaller in diameter. An M16A1 pencil barrel is 0.600: diameter after of the front sight, do you really want to make it just over 1/2 inch in diameter? For stiffness and heat control reasons, barrels are much thicker (and stronger) than they need to be just for containing pressure. So, there is really no value is increased strength.

    The only other major difference between the two is the hardness, all of three points. The allowable hardness of an M16/M4 barrel is RHc 26 to 32, which actually can be met with either steel...

    So, how much longer will a 4150 barrel last over a 4150 barrel? A few hundred rounds?

    (Oh, and before anyone jumps on the 41V50/CMV is the"ultimate", the conclusion of "Comparative Evaluation of Chromium Plated M14 Rifle Barrels Fabricated from Chromc-Moly-Vanadium Steel and ORD 4150 Resulphurized Steel, MIL-S-11595 (ORD)," Springfield Armory, August 1959 states:

    "Chromium plated ORD 4150 resulphurized steel and chromium plated chrome-moly-vanadium steel . . . barrels performed very well in endurance and sustained fire tests. Based on the results of this test, equal performance characteristics were exhibited by the two types of barrel steels."

    There is not a lot of difference between 4150 and 41V50.)
    Last edited by lysander; 03-27-23 at 10:23.

  7. #17
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    Quote Originally Posted by lysander View Post
    Given that the difference between 4140 and 4150 is all of 0.10% carbon (or about 0.0000625 ounces, in your average barrel), just exactly how much longer will it last?

    A bar of normalized 4140 has the following properties:

    Hardness - HB 302 / RHb 99 / RHc 32 / HV 319
    Ultimate Tensile - 148 ksi
    Yield Tensile - 95 ksi
    Elongation - 17.7%
    Reduction - 46.8%
    Mod of Elasticity - 29,700 ksi
    Bulk Modulus - 23,200 ksi
    Poissons Ratio - 0.29
    Shear Modulus - 11,600 ksi

    A bar of normalized 4150 has the following properties:

    Hardness - HB 321 / RHb 99 / RHc 35 / HV 339
    Ultimate Tensile - 168 ksi
    Yield Tensile - 107 ksi
    Elongation - 11.7%
    Reduction - 31%
    Mod of Elasticity - 29,700 ksi
    Bulk Modulus - 23,200 ksi
    Poissons Ratio - 0.29
    Shear Modulus - 11,600 ksi

    The first thing someone will shout is that 4150 is 20 ksi stronger, but in this case the yield strength is more important. While you don't want blow apart (ultimate failure), you don't want it to bend or bulge, so the practical difference in the strength is only 12 ksi. So we can make a smaller barrel, Right? For a 70,000 psi proof load, the barrel can be all of 0.086" smaller in diameter. An M16A1 pencil barrel is 0.600: diameter after of the front sight, do you really want to make it just over 1/2 inch in diameter? For stiffness and heat control reasons, barrels are much thicker (and stronger) than they need to be just for containing pressure. So, there is really no value is increased strength.

    The only other major difference between the two is the hardness, all of three points. The allowable hardness of an M16/M4 barrel is RHc 26 to 32, which actually can be met with either steel...

    So, how much longer will a 4150 barrel last over a 4150 barrel? A few hundred rounds?

    (Oh, and before anyone jumps on the 41V50/CMV is the"ultimate", the conclusion of "Comparative Evaluation of Chromium Plated M14 Rifle Barrels Fabricated from Chromc-Moly-Vanadium Steel and ORD 4150 Resulphurized Steel, MIL-S-11595 (ORD)," Springfield Armory, August 1959 states:

    "Chromium plated ORD 4150 resulphurized steel and chromium plated chrome-moly-vanadium steel . . . barrels performed very well in endurance and sustained fire tests. Based on the results of this test, equal performance characteristics were exhibited by the two types of barrel steels."

    There is not a lot of difference between 4150 and 41V50.)
    As someone who is neither engineer nor metallurgist, I’ve always ASSumed that if 4140 is not superior to 4150, the most logical reason to use it is cost savings. While sometimes cheaper materials are just as good, when the use of them goes against industry and customer (.mil) standards, then it is an example of a corner cut, that leaves me wondering what other measures were used to reach that price-point. Is that a bad assessment?

    As far as durability vs difficulty to manufacture with various types of stainless and carbon steels, it makes sense to me that steels more resistant to shedding material as a hot metallic object chased by hot fluids and solids abrade it at high pressure would be more difficult/costly to machine. I’ve read that stainless is easier on tooling and cuts more easily, so that is why for barrels where a near-perfect bore is more important than durability, stainless is popular. I think some barrel manufacturer made that claim, but don’t remember for sure. Makes sense to me.
    Last edited by 1168; 03-27-23 at 10:50.

  8. #18
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    Quote Originally Posted by lysander View Post
    Given that the difference between 4140 and 4150 is all of 0.10% carbon (or about 0.0000625 ounces, in your average barrel), just exactly how much longer will it last?

    A bar of normalized 4140 has the following properties:

    Hardness - HB 302 / RHb 99 / RHc 32 / HV 319
    Ultimate Tensile - 148 ksi
    Yield Tensile - 95 ksi
    Elongation - 17.7%
    Reduction - 46.8%
    Mod of Elasticity - 29,700 ksi
    Bulk Modulus - 23,200 ksi
    Poissons Ratio - 0.29
    Shear Modulus - 11,600 ksi

    A bar of normalized 4150 has the following properties:

    Hardness - HB 321 / RHb 99 / RHc 35 / HV 339
    Ultimate Tensile - 168 ksi
    Yield Tensile - 107 ksi
    Elongation - 11.7%
    Reduction - 31%
    Mod of Elasticity - 29,700 ksi
    Bulk Modulus - 23,200 ksi
    Poissons Ratio - 0.29
    Shear Modulus - 11,600 ksi

    The first thing someone will shout is that 4150 is 20 ksi stronger, but in this case the yield strength is more important. While you don't want blow apart (ultimate failure), you don't want it to bend or bulge, so the practical difference in the strength is only 12 ksi. So we can make a smaller barrel, Right? For a 70,000 psi proof load, the barrel can be all of 0.086" smaller in diameter. An M16A1 pencil barrel is 0.600: diameter after of the front sight, do you really want to make it just over 1/2 inch in diameter? For stiffness and heat control reasons, barrels are much thicker (and stronger) than they need to be just for containing pressure. So, there is really no value is increased strength.

    The only other major difference between the two is the hardness, all of three points. The allowable hardness of an M16/M4 barrel is RHc 26 to 32, which actually can be met with either steel...

    So, how much longer will a 4150 barrel last over a 4150 barrel? A few hundred rounds?

    (Oh, and before anyone jumps on the 41V50/CMV is the"ultimate", the conclusion of "Comparative Evaluation of Chromium Plated M14 Rifle Barrels Fabricated from Chromc-Moly-Vanadium Steel and ORD 4150 Resulphurized Steel, MIL-S-11595 (ORD)," Springfield Armory, August 1959 states:

    "Chromium plated ORD 4150 resulphurized steel and chromium plated chrome-moly-vanadium steel . . . barrels performed very well in endurance and sustained fire tests. Based on the results of this test, equal performance characteristics were exhibited by the two types of barrel steels."

    There is not a lot of difference between 4150 and 41V50.)
    Why does the military spec 4150CMV?
    Maybe they don't want to make the barrel smaller in diameter but only make a small diameter barrel stronger.
    I read a report somewhere in the last few days that said in case of an obstruction IIRC the SCAR and HK416 barrel was fired it would not explode but a Colt barrel will.
    As for personal experience, I have drilled apx 70,000 gas ports in barrels personally over a 14 year period. Barrels made of 4140 and then Melonite treated are easier to drill than 4150 barrels with the same treatment. The case hard created by the Melonite/nitride treatment is harder and thicker on the 4150cmv barrels which tells me the lands will not wear as fast.
    I assume people buying barrels will decide if they want to purchase a 4140, 4150 or CHF barrel, chromelined or not based upon what they read on the internet LOL.

    Concern of rupture-https://apps.dtic.mil/sti/pdfs/ADA317929.pdf

    another clip-"In fact, it is not even possible that an M4 barrel can heat up to the point of being white hot. M4 barrels are made from Alloy Steel 4150. The melting point of this steel is 1426 degrees Celsius. For steel to go white, it needs to be over 1400 degrees Celsius.

    The Ground Precautionary Message ACALA #97-031, from November 1996, clearly states that if an M4 barrel reaches just 737 degrees Celcius, the barrel will be weaked to the point where burst."

    "last longer" could mean different things, wear/accuracy or rupturing.

    https://smallarmssolutions.com/home/...rearms-tell-us
    Last edited by constructor; 03-27-23 at 14:41.

  9. #19
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    Quote Originally Posted by constructor View Post
    Why does the military spec 4150CMV?
    Maybe they don't want to make the barrel smaller in diameter but only make a small diameter barrel stronger.
    I read a report somewhere in the last few days that said in case of an obstruction IIRC the SCAR and HK416 barrel was fired it would not explode but a Colt barrel will.
    As for personal experience, I have drilled apx 70,000 gas ports in barrels personally over a 14 year period. Barrels made of 4140 and then Melonite treated are easier to drill than 4150 barrels with the same treatment. The case hard created by the Melonite/nitride treatment is harder and thicker on the 4150cmv barrels which tells me the lands will not wear as fast.
    I assume people buying barrels will decide if they want to purchase a 4140, 4150 or CHF barrel, chromelined or not based upon what they read on the internet LOL.
    There is another professional forum made up of military insiders from several different countries, they discuss these topics in depth. https://forums.delphiforums.com/autogun

    Concern of rupture-https://apps.dtic.mil/sti/pdfs/ADA317929.pdf

    another clip-"In fact, it is not even possible that an M4 barrel can heat up to the point of being white hot. M4 barrels are made from Alloy Steel 4150. The melting point of this steel is 1426 degrees Celsius. For steel to go white, it needs to be over 1400 degrees Celsius.

    The Ground Precautionary Message ACALA #97-031, from November 1996, clearly states that if an M4 barrel reaches just 737 degrees Celcius, the barrel will be weaked to the point where burst."

    "last longer" could mean different things, wear/accuracy or rupturing.

    https://smallarmssolutions.com/home/...rearms-tell-us
    4140 nitrided vs 4150 nitrided - It's either your imagination, or they weren't treated the same. The end hardness of nitriding is the result of the nitride layer thickness. And the "toughness" and "machineability"of 4140 and 4150 in the hardened state is the same.

    SCAR/HK vs M4 - I have read that report. It compares the H&K barrel, which is 25 mm (1 inch) in diameter, and the SCAR barrel, which is also 25 mm (1 inch) in diameter to the barrel of an M4 which is between 0.60" and 0.70" ( 15.25 and 17.75mm), which do you think will be able to handle an obstruction better?

    As to overheating and failure - the transformation temperature of 4140 and 4150 are the same, which means they will loss strength at he same temperature, so the number of rounds before popping will be pretty much the same.

    And let's be honest - how often is the average AR owner going even start approaching 800° F, let alone get it near 1400° F (740° C)

    So, what are the great advantages of 4150 over 4140? Even if the 4150 last longer, the question is does it last enough longer to justify the extra cost?

  10. #20
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    Quote Originally Posted by lysander View Post
    4140 nitrided vs 4150 nitrided - It's either your imagination, or they weren't treated the same. The end hardness of nitriding is the result of the nitride layer thickness. And the "toughness" and "machineability"of 4140 and 4150 in the hardened state is the same.

    SCAR/HK vs M4 - I have read that report. It compares the H&K barrel, which is 25 mm (1 inch) in diameter, and the SCAR barrel, which is also 25 mm (1 inch) in diameter to the barrel of an M4 which is between 0.60" and 0.70" ( 15.25 and 17.75mm), which do you think will be able to handle an obstruction better?

    As to overheating and failure - the transformation temperature of 4140 and 4150 are the same, which means they will loss strength at he same temperature, so the number of rounds before popping will be pretty much the same.

    And let's be honest - how often is the average AR owner going even start approaching 800° F, let alone get it near 1400° F (740° C)

    So, what are the great advantages of 4150 over 4140? Even if the 4150 last longer, the question is does it last enough longer to justify the extra cost?
    You are free to choose whatever kind of barrel you want based on whatever you believe.
    The report I saw was using typical govt profile barrels as in the contract barrel HK used on the 416 and what FN used on their Fn15 and SCAR16
    I pay apx $10 extra per barrel to use 4150 and they all go to the same place for Melonite treatment and are placed in the vats at the same temperature and same length of time.

    For everyone else I suggest reading this- https://smallarmssolutions.com/home/...rearms-tell-us Everyone likes to repeat the quote "remember your mil-spec" rifle was built by the lowest bidder" Yes but it was built per the mil spec, TDP or FN,LMT,KAC version...big difference from a civilian grade rifle that can use anything.

    A paragraph from within the article.-----"What I hope the reader takes away from this is that all AR’s are not created equal. That these weapons are a system. When something is altered from the system bad things can happen. The standard to how an M16/M4 rifle functions and holds up is the Mil-Spec rifle and ammunition. The hodge podge of parts put together rifles in this industry are not held to any standard. Many manufactures have no drawing or TDP’s. They just buy the cheapest generic AR parts that they can buy and assemble rifles. The attitude is these are commercial and they don’t have to go to the extremes that government contractors must do to ensure they are battle rifles."
    Last edited by constructor; 03-27-23 at 17:02.

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