Which BCG should I get?

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    omegared24

    Ultimate Member
    Dec 23, 2011
    4,747
    Ijamsville, MD
    calicojack said:
    Wow - I thought all the PSA BCG's were chrome lined; guess not.

    I need to go through my BCG's and check. I also have Rock River BCG's. I know all of the gas keys staked well, that I did check.
    Click to expand...

    Nitride BCG's don't have chrome lining. At least none that I have seen. Nitriding provides it's own protection.

    That's part of the issue with nitride BCG's not gauging properly. When a carrier is chrome lined it adds that thickness that puts it in spec. If it doesn't get the chrome lining then it will let a larger gauge pass through. Nitriding isn't a coating like chrome.

    I suspect that many base bolts and carriers (prior to coatings or treatment) are coming from several sources that send them at a certain spec. Then they get NiB, nitrided, phosphate...which changes that spec based on the coating.
     
    DutchV

    DutchV

    Ultimate Member
    Jul 8, 2012
    4,731
    calicojack

    calicojack

    American Sporting Rifle
    MDS Supporter
    May 29, 2018
    5,420
    Cuba on the Chesapeake
    outrider58 said:
    I have my favorites, but if you're starting off blind, I tell people to make sure the recess for the bolt is chrome lined as well as the gas key. Make sure the gas key screws don't have lettering on them or that it is advertised as having grade 8 gas key screws. None of this guarantees a perfect BCG, but it's a good place to start.
    Click to expand...

    I was wondering what Grade 8 means:

    "Grade 8 bolts are comprised of carbon alloy steel, thus giving them a high psi rating. Zinc or yellow zinc grade 8 bolts are available to resist corrosion. The factor that makes a grade 8 bolt different from a lower grade bolt is its preload strength. Higher grade materials, such as carbon alloy steel, allow for greater torque strength in the threads of the bolt. The preload, or thread tension in a fastener is higher when the type of steel being used is grade 8 in quality. Mark's Standard Handbook for Mechanical Engineers lists Grade 8's as 150 ksi fasteners meaning the tensile strength is 150,000 lbs per square inch.

    Grade 8 bolts are medium carbon alloy steel, quenched and tempered at a minimum temperature of 800 degrees Fahrenheit. They are then heat-treated to achieve a hardness of 33 to 39 on the Rockwell C scale."
     
    outrider58

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    50,068
    calicojack said:
    I was wondering what Grade 8 means:

    "Grade 8 bolts are comprised of carbon alloy steel, thus giving them a high psi rating. Zinc or yellow zinc grade 8 bolts are available to resist corrosion. The factor that makes a grade 8 bolt different from a lower grade bolt is its preload strength. Higher grade materials, such as carbon alloy steel, allow for greater torque strength in the threads of the bolt. The preload, or thread tension in a fastener is higher when the type of steel being used is grade 8 in quality. Mark's Standard Handbook for Mechanical Engineers lists Grade 8's as 150 ksi fasteners meaning the tensile strength is 150,000 lbs per square inch.

    Grade 8 bolts are medium carbon alloy steel, quenched and tempered at a minimum temperature of 800 degrees Fahrenheit. They are then heat-treated to achieve a hardness of 33 to 39 on the Rockwell C scale."
    Click to expand...

    Do you know how to check for proper torque on gas key screws?
     
    M

    Mule

    Just Mule
    MDS Supporter
    Sep 14, 2013
    661
    clandestine said:
    Banned!

    Just kidding.
    Click to expand...

    At the build class I'd attended, you'd told us it was OK to browse your parts and tool inventory, as long as we did so respectfully. So, during some down time, I did.

    A few weeks later, I had a dream that I was in another one of your classes, and I was looking at your parts boxes there, also.

    Apparently, though, unbeknownst to dream-me, you hadn't made the same offer to the dream-class. So, when dream-you saw me over in the corner, examining one of your gauges, dream-you stopped the class, and asked what dream-me was doing.

    When I let dream-you know, he told me to pack up my things, and said I wouldn't be permitted to take any more SOTAR courses in the future.

    At that point, I awakened from the dream. However, I wasn't fully awake yet, and still believed it'd all been real. I was devastated, horrified that I'd let you down, and couldn't believe that I wouldn't be able to take any more of your classes.

    So, when I saw your post, I had a flashback to that terrifying morning.
    :)



    Getting back to the topic of the thread, do you have any thoughts or input on Cross Machine Tool's BCGs?
     
    holesonpaper

    holesonpaper

    Active Member
    Mar 10, 2017
    929
    Hazzard county
    grimnar15 said:
    Are the Sharps and Rubber City BCGs any good?
    Click to expand...

    Noveske was OEMing Rubber City BCG's for a while several years ago - not sure if they still are... Back then I picked up 2-3 and all and all, they worked and I liked however at a SOTAR class, Chad inspected and the gas key intake diameter was slightly larger than it should (which I believe can lead to issues). If I recall corrected I think they nitrided a key designed for chroming. Addionally I believe the bolts were YHM or whatever that foreign manufacturer was but that may have changed.

    I have the tools an extra keys to replace if needed, but haven't had a reason to yet.

    I never had any problems with and still use in one of my rifles..
     
    clandestine

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,032
    Elkton, MD
    Mule said:
    At the build class I'd attended, you'd told us it was OK to browse your parts and tool inventory, as long as we did so respectfully. So, during some down time, I did.

    A few weeks later, I had a dream that I was in another one of your classes, and I was looking at your parts boxes there, also.

    Apparently, though, unbeknownst to dream-me, you hadn't made the same offer to the dream-class. So, when dream-you saw me over in the corner, examining one of your gauges, dream-you stopped the class, and asked what dream-me was doing.

    When I let dream-you know, he told me to pack up my things, and said I wouldn't be permitted to take any more SOTAR courses in the future.

    At that point, I awakened from the dream. However, I wasn't fully awake yet, and still believed it'd all been real. I was devastated, horrified that I'd let you down, and couldn't believe that I wouldn't be able to take any more of your classes.

    So, when I saw your post, I had a flashback to that terrifying morning.
    :)



    Getting back to the topic of the thread, do you have any thoughts or input on Cross Machine Tool's BCGs?
    Click to expand...

    I just saw this. That's terrible. :(
     
    G

    grimnar15

    Ultimate Member
    MDS Supporter
    Jul 21, 2019
    1,645
    Mule said:
    At the build class I'd attended, you'd told us it was OK to browse your parts and tool inventory, as long as we did so respectfully. So, during some down time, I did.

    A few weeks later, I had a dream that I was in another one of your classes, and I was looking at your parts boxes there, also.

    Apparently, though, unbeknownst to dream-me, you hadn't made the same offer to the dream-class. So, when dream-you saw me over in the corner, examining one of your gauges, dream-you stopped the class, and asked what dream-me was doing.

    When I let dream-you know, he told me to pack up my things, and said I wouldn't be permitted to take any more SOTAR courses in the future.

    At that point, I awakened from the dream. However, I wasn't fully awake yet, and still believed it'd all been real. I was devastated, horrified that I'd let you down, and couldn't believe that I wouldn't be able to take any more of your classes.

    So, when I saw your post, I had a flashback to that terrifying morning.
    :)



    Getting back to the topic of the thread, do you have any thoughts or input on Cross Machine Tool's BCGs?
    Click to expand...

    Creepy shit.
     
    M

    Melnic

    Ultimate Member
    MDS Supporter
    Dec 27, 2012
    15,376
    HoCo
    outrider58 said:
    Only PSA thing I ever bought was one of their bolts. Admittedly, it was a Black Friday special. After a couple years of it sitting in my parts bin, I put it into a build. Gun refused to cycle. Even suppressed with adjustable gas block. I finally eliminated everything but the bolt. Tore it down and 'rebuilt' it and the gun runs like a top.

    PSA says OOS. I'd wait and get this...https://www.armorally.com/shop/toolcraft-5-56-223-chrome-phosphate-bolt-carrier-group/

    ...or this...https://www.righttobear.com/AO-Precision-Phosphate-Bolt-Carrier-Group-158-HP-p/aom16-hpt-mpi.htm
    Click to expand...

    The AO Precision is $89 right now. Don't know if its one of those "perpetual" sales but I ordered 2 to fill gaps in my Uppers. These are for "range toys"
     
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