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Thread: Help w/ 10.3 10.5 SBR...

  1. #1
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    Help w/ 10.3 10.5 SBR...

    The Situation:
    My current SBR (300blk) is shot suppressed and unsuppressed equally and I really like not having to tune or adjust the gas block. I want a 5.56 upper that is no longer than 10.5" but will also allow me to shoot suppressed/unsuppressed equally reliable.

    I decided on the mk18 barrel length and gas system as that was designed to function regardless of suppressor use. Furthermore with the amount of r&d and t&e that went into it, I feel comfortable in terms of its overall reliability and function.

    The Problem:
    I cannot find ANY 10.3" or 10.5" barrels that have the NSWC spec .070" gas port or even the standard .063" (which I could open up). I just got off the phone with Daniel Defense who stated their 10.3" is a .086" port. I understand the purpose of the larger ports is to cycle less powerful ammo, but I think that will be way over gassed with a can attached.

    The Plea for Help:
    Does anyone have any leads on a 10.3-.5" barrel that has the smaller gas port I'm after?
    Is my only solution to buy a longer barrel and have it cut down?
    Can anyone chime in with their experience running 10.5 both suppressed and unsuppressed with a STANDARD gas block?

  2. #2
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    Are you after a fixed front sight base?

    I'm in your exact position. I'm pretty sick of these companies overgassing everything to cater to the mouth breather crowd.

    You can get an LMT 10.5 upper with the receiver at DSGarms for $485. They show "available". They are reported to have the .071" gas port. I finally threw in the towel and bought an Aeroprecision 10.5 with the .077" port. I don't plan to run a can, so I figure I can rein it in with a heavier buffer.
    "You people have too much time on your hands." - scottryan

  3. #3
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    Quote Originally Posted by markm View Post
    Are you after a fixed front sight base?

    I'm in your exact position. I'm pretty sick of these companies overgassing everything to cater to the mouth breather crowd.

    You can get an LMT 10.5 upper with the receiver at DSGarms for $485. They show "available". They are reported to have the .071" gas port. I finally threw in the towel and bought an Aeroprecision 10.5 with the .077" port. I don't plan to run a can, so I figure I can rein it in with a heavier buffer.
    Thanks for your reply, but to answer your question; no. I'm not after a fixed front sight. I'd prefer a low profile so I can tuck it under the rail. Although, the mk18 calls for the mk12 gas block...I'm unsure if there is a difference in port/hole diameter between a standard say BCM gas block and the DD or Badger gas block. In other words, will a standard .750 gas block function the same as the Mil-spec MK12 gas block?

  4. #4
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    I may be wrong, because I don't follow every new thing that pops up, but I believe that the MK12 block is the same, just lower profile.

    The standard port size for a MK18 as recently confirmed in two separate emails from LMT to people is .071 (Crane spec). The last Rainier Arms barrel I looked at (10 days ago) was ported at .071 verified with a set of pin gages.

    And you won't find a 10.3"/10.5" barrel with an .063 port because they don't exist. You would need to start with an M4 carbine barrel (correctly made) and then have the barrel cut and opened.

    http://www.rainierarms.com/rainier-a...rrel-10-5-6545

    Quote Originally Posted by sidewaysil80 View Post
    Thanks for your reply, but to answer your question; no. I'm not after a fixed front sight. I'd prefer a low profile so I can tuck it under the rail. Although, the mk18 calls for the mk12 gas block...I'm unsure if there is a difference in port/hole diameter between a standard say BCM gas block and the DD or Badger gas block. In other words, will a standard .750 gas block function the same as the Mil-spec MK12 gas block?



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  5. #5
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    I was looking at those Rainier barrels the other day. They look pretty nice.
    "You people have too much time on your hands." - scottryan

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    This threads solution goes back once again to the the Syrac or SLR gas blocks. They work to tame down the monster port barrels with ease. Lot easier solution. My SLR on BCM 11.5 is over 1.5K without an issue suppressed 100% of the time. Still works great with the can off too. While I too, have been cutting down car barrels to length with smaller ports. Sometimes the easiest solution is a well made adjustable gas block. While I don't have them on all of my suppressed SBR's, it is a very good solution for those few problem rifles.. Just my .02

    Edit.. With the many many adjustment clicks now on the gas blocks, you can pretty much dial it in to work with or without a can. And if you for some reason bought some crap ammo. Open it up a few clicks and your still good to go. I however, do not adjust mine. I found the sweet spot 4 clicks from closed. H2 buffer, car spring. Runs like a champ with and without a suppressor with 5.56 ammo. Easy solution to buying a different barrel, sending it off, having it cut and back together again.
    Last edited by Jwknutson17; 01-15-15 at 11:53.
    Philippians 4:13

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    True. But I want an FSB blaster.

    Rainier lists my DREAM barrel, but it's out of stock. 10.5 Noveske FSB Chrome lined. I'd even pay the ridiculous Noveske price to get that thing.
    "You people have too much time on your hands." - scottryan

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    16" DD barrel carbine gas

    Cut to 10.3". Don't adjust the gas port.

    H buffer, Enhanced carrier - done.
    Why do the loudest do the least?

  9. #9
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    Quote Originally Posted by Eurodriver View Post
    16" DD barrel carbine gas

    Cut to 10.3". Don't adjust the gas port.

    H buffer, Enhanced carrier - done.
    I actually pulled out an old Bushmaster 14.5" carbean, and the port is a perfect .071 +/-. I was thrilled! All I had to do was find a lathe monkey. Then I checked the leade and I'm getting like .221 bullet jump. (.147" is 5.56 spec if I remember right)

    I couldn't put $50 in cut and thread into a worn barrel like that.
    "You people have too much time on your hands." - scottryan

  10. #10
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    Any reason you're not interested in a Switchblock upper? Or what about something like the MicroMOA Govnah? Or, if you're not adverse to piston guns, there's always the PWS MK110 or one of the LWRCi ICA5 uppers (long stroke and short stroke, respectively, though markm will probably tell you his opinions on LWRC). None of these options have to fiddle with counting the number of clicks to adjust the gas block properly, and are easy to switch from different settings without the need for a little hex key or anything, unlike the typical adjustable gas blocks. I personally use the MicroMOA Govnah on my 14.5" (Centurion Arms 16" midlength cut down to 14.5") and a PWS MK110, paired with a Surefire SOCOM 5.56 and a lower with the Vltor A5 (with the stock Vltor A5 buffer), and have had not any issues with either upper, although I have admittedly low round counts through them.

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