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Thread: SBR in 7.62x39mm Questions

  1. #21
    Marksman Oddux's Avatar
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    Re: SBR in 7.62x39mm Questions

    Interesting thread. When I purchased my XCR, I ordered it specifically with a mini-upper (even though the current 5.56 barrel is full length) so that I could get the 7.62x39 barrel later in an SBR length, if I purchase the 10in barrel for the mini-length upper would I have any problems with the gas ports or suppressor use?

  2. #22
    XCR Guru Merlin's Avatar
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    Re: SBR in 7.62x39mm Questions

    Quote Originally Posted by Oddux View Post
    Interesting thread. When I purchased my XCR, I ordered it specifically with a mini-upper (even though the current 5.56 barrel is full length) so that I could get the 7.62x39 barrel later in an SBR length, if I purchase the 10in barrel for the mini-length upper would I have any problems with the gas ports or suppressor use?
    The 10" barrel should come with or require it's own recoil rod I think, the ports and gas block would be correct for that length barrel. The minimum 12" recommendation for suppressor use is by the suppressor manufacturers as they feel you need as least a 12" barrel to stabilize the bullet and not have baffle strikes. YHM says anything less than 12" IIRC voids their suppressor warranty.

    "Be Vigilant and Safe!!"
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  3. #23
    Rob
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    Re: SBR in 7.62x39mm Questions

    Quote Originally Posted by Merlin View Post
    Quote Originally Posted by Oddux View Post
    Interesting thread. When I purchased my XCR, I ordered it specifically with a mini-upper (even though the current 5.56 barrel is full length) so that I could get the 7.62x39 barrel later in an SBR length, if I purchase the 10in barrel for the mini-length upper would I have any problems with the gas ports or suppressor use?
    The 10" barrel should come with or require it's own recoil rod I think, the ports and gas block would be correct for that length barrel. The minimum 12" recommendation for suppressor use is by the suppressor manufacturers as they feel you need as least a 12" barrel to stabilize the bullet and not have baffle strikes. YHM says anything less than 12" IIRC voids their suppressor warranty.
    I am not sure which manufacturer I recently had this email exchange with (either AAC or YHM) but the 12" minimum is for 5.56. If you use a 7.62 can, they waranty it for 7.5" in both .300 BLK and on a 7.5" 5.56 based on a recent e-mail communication i had with them.

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  5. #24
    XCR Guru Merlin's Avatar
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    Re: SBR in 7.62x39mm Questions

    They must have changed their policy, for this is the answer I got from YHM when I asked a while back. I was incorrect by .5".

    Sir,
    The minimum recommended barrel length for the Phantom 7.62 if used on any .30 caliber is 12.5 inches. If you wanted to use the sound suppressor on a 5.56, which you can with no problems, then you may go down to a 10.5 inch barrel when used on a 5.56.

    "Be Vigilant and Safe!!"
    "Molon Labe!!"
    "It Is A Weak Man Who Urges Compromise!!"

  6. #25
    XCR Guru Sean K.'s Avatar
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    Re: SBR in 7.62x39mm Questions

    Quote Originally Posted by Merlin View Post
    Quote Originally Posted by Oddux View Post
    Interesting thread. When I purchased my XCR, I ordered it specifically with a mini-upper (even though the current 5.56 barrel is full length) so that I could get the 7.62x39 barrel later in an SBR length, if I purchase the 10in barrel for the mini-length upper would I have any problems with the gas ports or suppressor use?
    The 10" barrel should come with or require it's own recoil rod I think, the ports and gas block would be correct for that length barrel. The minimum 12" recommendation for suppressor use is by the suppressor manufacturers as they feel you need as least a 12" barrel to stabilize the bullet and not have baffle strikes. YHM says anything less than 12" IIRC voids their suppressor warranty.
    A 10" bbl with mini length gas block placement *shouldn't* require any port work to run 100%, but it will require the mini length gas tube and op rod if you only have the standard length gas tube and op rod now.

    HTH,
    Sean
    "Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger

  7. #26
    XCR Guru Sean K.'s Avatar
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    Re: SBR in 7.62x39mm Questions

    Quote Originally Posted by Rob View Post
    Quote Originally Posted by Merlin View Post
    Quote Originally Posted by Oddux View Post
    Interesting thread. When I purchased my XCR, I ordered it specifically with a mini-upper (even though the current 5.56 barrel is full length) so that I could get the 7.62x39 barrel later in an SBR length, if I purchase the 10in barrel for the mini-length upper would I have any problems with the gas ports or suppressor use?
    The 10" barrel should come with or require it's own recoil rod I think, the ports and gas block would be correct for that length barrel. The minimum 12" recommendation for suppressor use is by the suppressor manufacturers as they feel you need as least a 12" barrel to stabilize the bullet and not have baffle strikes. YHM says anything less than 12" IIRC voids their suppressor warranty.
    I am not sure which manufacturer I recently had this email exchange with (either AAC or YHM) but the 12" minimum is for 5.56. If you use a 7.62 can, they waranty it for 7.5" in both .300 BLK and on a 7.5" 5.56 based on a recent e-mail communication i had with them.
    Must be mfr. dependent....most 5.56 can mfrs require at least 10.5" of bbl to warranty the can. This is the first I've heard of a 12" minimum for 5.56. Not sure on 7.62x39.......
    "Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger

  8. #27
    Banned EricCartmann's Avatar
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    Re: SBR in 7.62x39mm Questions

    Quote Originally Posted by Sean K. View Post
    Quote Originally Posted by Rob View Post
    Quote Originally Posted by Merlin View Post
    Quote Originally Posted by Oddux View Post
    Interesting thread. When I purchased my XCR, I ordered it specifically with a mini-upper (even though the current 5.56 barrel is full length) so that I could get the 7.62x39 barrel later in an SBR length, if I purchase the 10in barrel for the mini-length upper would I have any problems with the gas ports or suppressor use?
    The 10" barrel should come with or require it's own recoil rod I think, the ports and gas block would be correct for that length barrel. The minimum 12" recommendation for suppressor use is by the suppressor manufacturers as they feel you need as least a 12" barrel to stabilize the bullet and not have baffle strikes. YHM says anything less than 12" IIRC voids their suppressor warranty.
    I am not sure which manufacturer I recently had this email exchange with (either AAC or YHM) but the 12" minimum is for 5.56. If you use a 7.62 can, they waranty it for 7.5" in both .300 BLK and on a 7.5" 5.56 based on a recent e-mail communication i had with them.
    Must be mfr. dependent....most 5.56 can mfrs require at least 10.5" of bbl to warranty the can. This is the first I've heard of a 12" minimum for 5.56. Not sure on 7.62x39.......
    It's the muzzle blast and the first baffle is what kills a suppressor. 5.56 is the highest pressure, it leaves the muzzle at 3000 fps! 7.62x39 has about 1/3rd the Velocity. Between 10.5" and 12.5" is huge difference in the difference in muzzle blast.

    For 5.56 to be safe I would not shoot suppressed anything less than 14.5" if you plan to shoot suppressed on a regular basis. For 7.62x39, I think 12.5" is very safe since it's 1/3rd the velocity. Keep in mind I pulled these barrel lengths at random, the key here is the longer the barrel the safer it is for your suppressor.

    Now for .300BLK, that is a slow moving round, so 7.5" should be safe.

    Either way it's easy to tell, just look at the first baffle and baffle erosion when you are done shooting. When I shoot 556 out of my 14.5" barrel, it looks like there is no wear and tear even after 500 rounds. For 556 and my 10.5" barrel, with only 100 rounds I see more erosion. For 7.5", man! I really wore down that first baffle after only 20 rounds. It appears there is more wear with 20 rounds out of 7.5" than when I shoot 1000 rounds out of 14.5". I am going to play around with a low pressure load for 5.56 to get the pressure down for my 7.5" upper.

  9. #28
    Marksman Dynamo55b's Avatar
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    Re: SBR in 7.62x39mm Questions

    Does strictly using low velocity / subsonic ammunition help? Thinking of putting a can on a 12inch.

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