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Thread: New BCM barrels

  1. #101
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    Quote Originally Posted by Col_Crocs View Post
    Really interesting... Phreakish, if you don't mind, what are your thoughts on nitrided barrels? Any plans of going that route in the future?
    Can't comment on plans for the future.

    As far as nitride, it's not easy to accomplish and in most cases the result is as good as, maybe even slightly better than, a typical forged and chrome lined barrel. The greatest benefit of nitride is the ability to protect and coat every part of the barrel, including the gas port. However, nitride treatment of an assembly is usually not done due to the molten salts getting between parts and continually weeping out over time. If the assembly isn't coated, then the gas port is likely going to be drilled after the nitride treated barrel is mated to an extension, in which case we lose a huge benefit of nitride and we're back to a part that's equivalent to a chrome lined barrel. That's not insignificant though, since chrome plating processes are finding their way ever closer to the center of the EPA's crosshairs and we'll need something to replace chrome when the day comes.

    Nitride treatment is also significantly different than the types of treatments the typical materials are given, so it would take some real engineering to ensure that the processes and materials are compatible to truly improve upon the hammer forged and chrome lined barrel, rather than degrade or simply meet the same performance threshold.

    TL;DR: There's a lot more to it than just tossing a barrel cluster in a salt tank. There's definitely benefits to be had, but it needs to be done right and even then the result is likely to be equivalent to and not hugely better than a chrome lined barrel, at least while chrome is still viable.

  2. #102
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    Quote Originally Posted by Phreakish View Post
    Can't comment on plans for the future.

    As far as nitride, it's not easy to accomplish and in most cases the result is as good as, maybe even slightly better than, a typical forged and chrome lined barrel. The greatest benefit of nitride is the ability to protect and coat every part of the barrel, including the gas port. However, nitride treatment of an assembly is usually not done due to the molten salts getting between parts and continually weeping out over time. If the assembly isn't coated, then the gas port is likely going to be drilled after the nitride treated barrel is mated to an extension, in which case we lose a huge benefit of nitride and we're back to a part that's equivalent to a chrome lined barrel. That's not insignificant though, since chrome plating processes are finding their way ever closer to the center of the EPA's crosshairs and we'll need something to replace chrome when the day comes.

    Nitride treatment is also significantly different than the types of treatments the typical materials are given, so it would take some real engineering to ensure that the processes and materials are compatible to truly improve upon the hammer forged and chrome lined barrel, rather than degrade or simply meet the same performance threshold.

    TL;DR: There's a lot more to it than just tossing a barrel cluster in a salt tank. There's definitely benefits to be had, but it needs to be done right and even then the result is likely to be equivalent to and not hugely better than a chrome lined barrel, at least while chrome is still viable.
    Love reading your posts Sir, Thanks!

  3. #103
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    Quote Originally Posted by Phreakish View Post
    As far as nitride...
    Thanks for responding and the insight.

  4. #104
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    Translation: START HOARDING CHROME LINED BARRELS just like BCGS!!!!
    "You people have too much time on your hands." - scottryan

  5. #105
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    Finally got a chance to weigh both a 14.5" Noveske Skinny barrel and a 14.5" BCM ELW-F barrel.
    These are the only two 14.5" continuous tapered, lightweight profile barrels I have found (maybe Sionics will join them?). That and the fact they are both made by tier 1 companies makes for an apt comparison. The Noveske is cold hammer forged "machine gun" spec steel w/ thicker chrome lining, and it has the handguard cap shoulder. Th details of BCMs awesome barrel can be found in this thread.


    14.5" Noveske Skinny barrel 20.85oz measured (stripped)
    14.5" BCM Standard ELW-Fluted 20.55oz measured (stripped)

  6. #106
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    Quote Originally Posted by Phreakish View Post
    I started to try Mohr's circle, but paint really sucks with circles so I gave up!

    1. Typical thermal expansion isn't typical. This is one of the reasons we favor the tapered profile, the uneven heat distribution down the bore means that to reduce the number of 'hot spots' the material making up the barrel ends up being uneven. I could go on for pages, but suffice to say we have a longer duration thermal event in the chamber and that event lasts less time the further down the barrel we get. This means more material (both for strength of the chamber as well as to sink heat) at the chamber end and less toward the muzzle. Any place we put a 'lump' of material will stay cooler during transient events and we'll expect to see local stresses which around other discontinuities (such as the gas port and block) might cause minor departures from straight. Not much, mind you, but it doesn't take much to subtend 3/4" at 100 yards.

    1 cont: button vs hammer forged: "steel is steel" and so the expansion, all things being equal, will be about the same. That said, the cold hammer forge process creates what we call residual stress. Basically, the steel is still under pressure once it's finished. For an applied load, the actual stress of the material starts from a negative (verus zero), and therefore can take much more load prior to hitting yield. How much more is highly dependent on many variables. This is especially true for the bore, where the vast majority of the cold work, and therefore the residual stress, is retained. We effectively create a barrel that has a stronger-than-normal (even though hardness is still close to the same) liner with a considerable wall thickness. The grain of the metal will also be refined and we'd expect to see long grains (since barrel blanks start short and end long) on the surface which are tightly packed together. The impact it has on overall expansion should be minimal, and given that the residual stress state is fairly uniform from end-to-end, we wouldn't expect to see any warpage when heated versus if the profile were less than uniform. We still have the same effects from other discontinuities, but all things equal the forged barrel still has the strength advantage with the residual stresses. The tighter grain structure also gives a superior surface for applying chrome and the higher quality surface will resist corrosion better due to the tightly packed grains (similar to the corrosion inhibition seen on polished surfaces, even when untreated). These are the major benefits of the hammer forged barrels: they resist wear better due to the residual stresses and better surface finish and the hard chrome tends to lay itself down in a more uniform and dense coating which increases the benefits offered by the chrome.

    2. That one is proprietary, but I will say we hold ours much tighter than what many suppliers can or are willing to provide.
    Awesome response. I loved hearing about the mechanics behind the hammer forging process. Us civils only deal with two types of steel, 36 or 50 ksi

    From an engineering standpoint, what are the advantages and disadvantages to stainless steel barrels?

  7. #107
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    Quote Originally Posted by Duke2424 View Post
    Awesome response. I loved hearing about the mechanics behind the hammer forging process. Us civils only deal with two types of steel, 36 or 50 ksi

    From an engineering standpoint, what are the advantages and disadvantages to stainless steel barrels?
    A stainless barrel is made to finished specs from the start. There's no chrome, no nitride, no other coatings that have to be applied or dealt with. This eliminates tolerance and finish issues. Chrome is one of those things that if done right it's awesome. If it's a tad rough, or inconsistent there's not much that can be done to fix it. Polishing is is tough because of it's hardness and if it's not a good consistent coating then there will be issues that can affect the bullet and thus accuracy.

    So, without the need for those coatings there are fewer steps involved (though the material costs more, is often more difficult to rifle and more difficult to machine) which means a more consistent bore. However, those same coatings that are used for corrosion resistance in steel barrels are also harder than the base steel. The omission of these coatings then makes a stainless barrel slightly more soft with respect to the bore. The result is shorter expected life, but better accuracy and consistency over it's lifespan.

    Rifles that see very low rounds per minute usage can see longevity that rival a CHF barrel, but those that have a fun switch or shoot high volumes in short times will see shorter life from a stainless barrel vs CHF.

  8. #108
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    Phreakish,

    Forgive me if this isn't the appropriate place to ask... but I have a Few Questions (sorry if it's already been asked elsewhere on this Forum):

    1. Any Plans to ever offer Other Chamberings in BCM Barrels? (300 Blk Out, 6.8 SPC, 6.5 Grendel etc.)
    2. Why aren't BCM Barrels offered in Complete Assemblies? *Are there Technical Reasons why the Gas Block and Gas Tube cannot be properly installed and secured from BCM? Basically, I would be looking for a quick and simple Solution to be able to Re-Barrel and need nothing more than a Torque Wrench and appropriate Barrel Nut Wrench...coming from an End User standpoint, with no real Amrorer or Depot Level Training Needed*
    3. Would a Geissele Reaction Rod be the most sensible Tool for doing Barrel/Muzzle Device/Gas Block Work or is there another preffered method you have?
    4. Should a BCM Bolt be ok with Virtually any BCM Receiver and Barrel, concerning Proper Headspacing?

    Thanks for all of the Knowledge you have already imparted in this thread, Sir. It is truly appreciated.
    Last edited by HD1911; 07-24-14 at 03:07.

  9. #109
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    With the popularity of the elw profile will we see ELW SS barrels for light weight AND extreme accuracy?

  10. #110
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    Quote Originally Posted by HD1911 View Post
    Phreakish,

    Forgive me if this isn't the appropriate place to ask... but I have a Few Questions (sorry if it's already been asked elsewhere on this Forum):

    1. Any Plans to ever offer Other Chamberings in BCM Barrels? (300 Blk Out, 6.8 SPC, 6.5 Grendel etc.)
    2. Why aren't BCM Barrels offered in Complete Assemblies? *Are there Technical Reasons why the Gas Block and Gas Tube cannot be properly installed and secured from BCM? Basically, I would be looking for a quick and simple Solution to be able to Re-Barrel and need nothing more than a Torque Wrench and appropriate Barrel Nut Wrench...coming from an End User standpoint, with no real Amrorer or Depot Level Training Needed*
    3. Would a Geissele Reaction Rod be the most sensible Tool for doing Barrel/Muzzle Device/Gas Block Work or is there another preffered method you have?
    4. Should a BCM Bolt be ok with Virtually any BCM Receiver and Barrel, concerning Proper Headspacing?

    Thanks for all of the Knowledge you have already imparted in this thread, Sir. It is truly appreciated.
    1) Can't comment on future plans.
    2) Simple reason: there are so many handguard choices that use different barrel nuts that to offer the plethora of combinations that we do, pre-assembled, would be an enormous task.
    3) I've never used a reaction rod, personal preference. I've seen all manner of failures from installing a muzzle device onto an assembled upper. In almost every case the torque applied to the muzzle device was way beyond reasonable or the barrel nut was installed too loose. It doesn't take much to ensure a brake or comp is snug. If it won't align close enough for reasonable torque to clock it properly with the supplied crush washer, then either a new crush washer, flipping the washer over, or sanding/filing the thickness slightly (and evenly) are far better approaches than herfing it down with a breaker bar. In the shop, we'll go through a few crush washers until hand-tight aligns well enough for reasonable torque to clock the comp.
    4) Our bolts are made to mil-spec standards. Any Mil spec barrel and extension should head space properly with our parts. That said, there's no way to know without checking with a head space gage. If the headspace check fails, it's usually in the barrel in my experience.

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