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Thread: Extractor Spring Question

  1. #11
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    Quote Originally Posted by toddackerman View Post
    Some definitions need to be made here:

    1. A carbine length gas system is typically in barrels that are 14.5" or shorter.

    2. A mid length gas system is typically in 16" barrels.

    I have had many more problems with installing the "O" Ring and high powered springs in my mid length MRP Upper (even after trying to break it in) than I ever had with just a Black Insert and a quality 4 coil USGI spring. My LMT MRP ran like a champ until I started reading all of the updates on the Crane "O" Ring, the "Defender", 5 coil springs etc.

    And then I was set straight by some members on this forum, and by Lewis Machine and Tool (the manufacturer of the MRP upper). The verdict...the "O" ring is only meant for gas systems that are more aggressive than the mid-length systems. LMY specifically stated t go back to the USGI extractor spring and black insert. (and yes I know they're putting "O" rings in all of their new bolts....go figure. Probably because you can always take the "O" ring out.)

    Another point....even AFTER BREAK IN....if a mid-length would run and not "Trap" rounds because of the excessive tension created from the "O" ring and high powered spring, who would want to have a weapon that isn't GTG after a routine maintenance procedure of replcing the spring and insert?

    The majority of 16" AR's out there are carbine gas system guns.

  2. #12
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    According to Sabre Defence when I called and asked, 5-coils + a black insert is current mil-spec for rifle, mid-length, and carbine. The rifle USED to be 4-coil with blue-buffer, but Sabre assured me that now everything was supposed to be 5-coil black buffer.

  3. #13
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    Well, did not notice some of these replies a while back.
    I'm very interested that the MRP owner above had trouble with the black buffer, and 5 coil extractor spring in his MRP. I too have just acquired an MRP, and I wonder how the LMT enhanced bolts with TWO springs are working in the MRP's? Guess I'll soon find out.
    I have only put 25 lousy rounds down range in my new MRP upper, but I was using a seperately purchased LMT 5.56 bolt, and it had the black buffer, 4-5 coil spring, and rubber O-ring.
    I say "4-5" coil extractor spring, because for the LIFE of me, I CANNOT figure out this whole "5 COIL" extractor spring!
    I have ordered NUMEROUS "5 coil extractor spring/Crane O Ring Kits" from BravoCompany, AND G&R Tactical, and ALL of them (EVERY SINGLE ONE OF THEM) has come to me with FOUR (yes, 4) coils. Not 5.
    I'm still trying to figure out why every picture I see on the net, shows 5 coils, but everytime I receive my order, the spring only has 4 coils.
    Not the biggest problem in the world, but I would just like to at least see, or recveive ONE spring that actually has 5 coils.
    Can anyone elaborate on this issue? Am I possibly getting 4 coils, with a "half" coil on each end, that then equates to 5?
    Honestly, I checked for this, each time, and I don't think that this is the case. I believe that I have received 4 coil springs from both G&R Tactical and BCM. Now I know these companies sell proper items, so I'm wondering if they were supplied the wrong items, or what?
    Can anyone help.
    Here is the pic from BCM's site, and you can clearly see FIVE full coils on this spring.
    ALL of my springs ordered from these two companies, look exactly like the picture below, except there are ONLY FOUR coils in each of my springs.
    Take a look. Wish I had a camera to post pics of all my FOUR coil springs.


    http://www.bravocompanyusa.com/BCM-E...%20upgrade.htm

  4. #14
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    IIRC. i think bravo company said that too many people were having problems with the tru 5 coil springs, so they had them reworked and they are more like 4 coils with more tension than stock ones. the website is not updated to reflect this as well.

    i have the BCM extractor spring upgrade kit sitting here on my desk too

  5. #15
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    Quote Originally Posted by theJanitor View Post
    IIRC. i think bravo company said that too many people were having problems with the tru 5 coil springs, so they had them reworked and they are more like 4 coils with more tension than stock ones. the website is not updated to reflect this as well.

    i have the BCM extractor spring upgrade kit sitting here on my desk too
    This is correct. BCM springs are so strong, that a fifth coil is not needed (especially when used with a black extractor insert and a Crane O-Ring).



    C4

  6. #16
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    Guys, what's the difference between the blue buffer insert, and the black one?
    I know the blue is RIFLE? and black is for our carbines (and some use black for any length gas system), but what are the physical differences between the two buffer inserts? Is the blue a WEAKER/SOFTER compound or lower durometer or what????
    I have always been surprised that swapping from blue to black could make much difference. I know just having some kind of insert inside the spring, will stiffen it, but does swapping from blue to black make that much difference?
    I would think the spring quality, and rubber O-Ring being added, would make the most difference, no?

  7. #17
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    [QUOTE=Paul Cataldo;167002]Guys, what's the difference between the blue buffer insert, and the black one?

    I know the blue is RIFLE? and black is for our carbines (and some use black for any length gas system), but what are the physical differences between the two buffer inserts? Is the blue a WEAKER/SOFTER compound or lower durometer or what????
    In the commercial market, black extractor inserts are generally stiffer.

    I have always been surprised that swapping from blue to black could make much difference. I know just having some kind of insert inside the spring, will stiffen it, but does swapping from blue to black make that much difference?
    I would think the spring quality, and rubber O-Ring being added, would make the most difference, no?
    You most likely wouldn't know the difference (especially if you are running a CS extractor spring and a Crane O-Ring). It is just one more piece of the puzzle to making the AR platform run as reliable as possible.

    C4

  8. #18
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    Quote Originally Posted by C4IGrant View Post
    This is correct. BCM springs are so strong, that a fifth coil is not needed (especially when used with a black extractor insert and a Crane O-Ring).C4
    The fewer coils a spring has, the stiffer it is. Adding more coils will make the spring not as stiff but it will also have less stress. So wire diameter being equal, a 4-coil will grab the case better but a 5 coil would last longer.

    http://www.weaponevolution.com/forum...Spring-Upgrade


    In that link the BCM spring is called a '5 coil spring' but it has 4 total coils (2 active coils). So it is a 4 coil spring.

    There are also photos of 3.5 and 4.5 coil springs there.

    Notice that the Colt spring, which is said to have the most force, is a 3.5 total coil spring (1.5 active coils).

    My thought is that since Colt took a fresh look at redesigning the spring, they set the force to be correct without an o-ring.
    Last edited by rsilvers; 07-27-10 at 22:57.

  9. #19
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    Quote Originally Posted by Razorhunter View Post
    I say "4-5" coil extractor spring, because for the LIFE of me, I CANNOT figure out this whole "5 COIL" extractor spring!
    I have ordered NUMEROUS "5 coil extractor spring/Crane O Ring Kits" from BravoCompany, AND G&R Tactical, and ALL of them (EVERY SINGLE ONE OF THEM) has come to me with FOUR (yes, 4) coils. Not 5.
    Worrying about the number of coils without actually knowing the spring rate is not going to get you anywhere. Someone can make a 5 coil spring that sucks, you have a good spring from a known source.

  10. #20
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    Quote Originally Posted by rsilvers View Post
    The fewer coils a spring has, the stiffer it is. Adding more coils will make the spring not as stiff but it will also have less stress. So wire diameter being equal, a 4-coil will grab the case better but a 5 coil would last longer.
    ......
    Last edited by 5shot; 07-28-10 at 15:53. Reason: I was wrong

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