ar-15 kit barrel

Discussion in 'Rifles' started by country_boy, Sep 26, 2009.

  1. country_boy

    country_boy TGT Addict

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    Feb 7, 2009
    Round Rock
    How important would it be to have a chrome lined barrel vs. regular barrel?
     


  2. jdh

    jdh Active Member

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    If you want the best accuracy and clean your rifle, go plain. If you just plan to blast away with questionable ammo and can't be bothered with proper maintenance get chrome lined.

    Or get a stainless barrel and have the best of both.
     
  3. Mate

    Mate Member

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    JDH hit the nail on the head, except that SS wont last as long as a regular barrel.
     
  4. ConnRadd

    ConnRadd Active Member

    Nice, I get to learn more....:icon_popcorn:
     
  5. TexasRedneck

    TexasRedneck 1911 Nut Lifetime Member

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    I've heard the same - that the SS won't last as long - but never an explanation as to "why" that made sense. I did some Googling, and found that the general consensus is that the steel is a better choice (generally) over the SS....Here's one explanation I found:
    (NOTE - this is NOT my "knowledge" below, but rather a cut and paste of an explanation that would appear unbiased and reasonably thought out)
    ************************

    To understand this subject, one must understand high-strength steel. For the record, I am a metallurgist by trade, and heat treat Quality Manager so I know enough about these steels. I do not like AISI 416 SS for gun barrels and I will explain why:

    To achieve the high strength the steel must possess to withstand the forces produced during firing, AISI 416 SS and/or AISI 4140/4150/4340 must be austenitized, quenched and tempered. After quenching, the average 416 SS will be about 40 Hardness Rockwell C (HRC) and 4000 grades about 50 HRC (To benefit those who do not know this scale, a file will be about 60 HRC, and a hammer will be about 30 HRC). In the "as quenched" state, the material is brittle and unstable. Tempering is employed to reduce the hardness to a "tough" state and stabilize the newly formed martensitic structure. In the case of 416 SS, and to get the hardness to about HRC 30 so it is able to be machined, one must temper at about 1075°F. This is not desirable as 416 SS shows a marked reduction in impact resistance when tempered between 700°F and 1100°F (temper imbrittlement). It will also show a marked decrease in corrosion resistance. 416 SS does still however exhibit better wear characteristics and corrosion resistance than the 4000 series high-strength grades mostly due to the higher chromium content. It is also readily available, inexpensive, and it looks good so manufacturers use it. The big problem though is that it is not as free-machining as the 4000 series grades so generally sulphur is added to alleviate that problem. What you then have is a microstructure with "sulphide stringers" in it that has been tempered in a bad tempering range so the impact resistance of the steel is very poor. Failures happen, and are not really wide-spread, but I will not buy a 416 SS barrel for that reason. The AISI 4140/4150/4340 grades do not have this temper imbrittlement problem, and show superior impact resistance when tempered to about 30 HRC. They are cheaper to buy in a production rifle. One who takes good care of a firearm will never have any major corrosion and wear issues with the 4000 grade steel barrels anyway. And if you do use it an awful lot and it begins to wear out, well then you got your money's worth from the product, just buy a new barrel. Nothing lasts forever anyway. As a note, AISI 410 SS is a better alternative to 416 SS as is does not generally have the sulphur issue, however the temper imbrittlement issue is still a concern.

    Here is my opinion: Unless you are competition shooter, buy the non-stainless grade barrels. If you are a professional match shooter find a good AISI 17-4PH barrel as it is a much better choice if one wants corrosion resistance, wear resistance, and impact resistance.

    For my money and safety, it is a 4000-series material.
     
  6. Okierifleman

    Okierifleman Active Member

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    Mar 14, 2009
    Houston
    I dont know where the topic of stainless came into the conversation, but the OP asked about a chrome lined barrel vs a alloy barrel. Carbon and alloy steels have very little if any corrosion resistance. Stainless is about twice the price as alloy, so to save money, they chrome line barrels to give them a bit of corrosion resistance and increased hardness in the bore so they last longer. A stainless barrel will last longer than an alloy barrel, because of the corrosion and increased wear resistance. But, it may not last longer than a chrome lined barrel because the chrome lining is harder than stainless.

    To put in a nutshell, if you are going to buy a barrel for your AR, be sure to get a chrome lined barrel, it will last longer than an unlined barrel. If you want to step up a notch, get a stainless match barrel.
     

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