9mm AR SBR questions

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  • rouchna

    Defund the ATF
    MDS Supporter
    Nov 25, 2009
    5,951
    Virginia
    I'm in the process of gathering parts to build a suppressed 9mm SBR. So far I have only ordered the lower and Upper. (Tirant 9 is still in jail)



    QC10 9mm Colt lower (Vltor-Matching Profile):







    Vltor MUR-1s Upper







    This is going to be registered as an SBR and be suppressed. Right now I'm debating between 5.5" and 7" barrels. I'm a VA resident so OAL is not an issue.



    I have a few questions and would appreciate any feedback.



    1. Any true benefit to the 7" over the 5.5"?



    2. Handguards: Should I get one that's a bit shorter than the barrel or go longer so that the suppressor can be partially covered.



    3. Any recommendations on handguards/rail? (will be running an AAC Tirant 9)



    4. Is the building process similar to an AR build? I'm going to be building the whole thing myself. I've built 5.56 ARs but never a 9mm. I'm assuming it's pretty similar with the exception of not needing a gas tube & block. Is this correct?



    5. Finally, any recommendation for buffers & bolts?



    Sorry for all the questions, but this will be my first 9mm AR build and I want to make sure I do it right from the get go.



    Thank you all for your help in advance.
     
    Last edited:

    CrawfishStu

    Creeper
    Dec 4, 2006
    2,337
    Crofton
    Bad news boss.

    1. ATF won't approve less than 29". So, 5 and 7 are out for barrel options.
    2. Get a handguard that will run over the suppressor.
    3. I love my wilson ff tubes. Do you like round or rails.
    4. You are right on with building it. Just like a .223.
    5. Get a heavy 9mm specific buffer it really helps with felt recoil and I run a CMMG bolt in both of mine and they are fine.
    6. If you get a barrell like an adco it can be threaded for 1/2x28. I have a TiRant45 and you can't get the 1/2x36 piston.
    7. Consider a sig brace and save yourself $200 and the longer barrel.
     

    Bertfish

    Throw bread on me
    Mar 13, 2013
    17,608
    White Marsh, MD
    Bad news boss.

    1. ATF won't approve less than 29". So, 5 and 7 are out for barrel options.
    2. Get a handguard that will run over the suppressor.
    3. I love my wilson ff tubes. Do you like round or rails.
    4. You are right on with building it. Just like a .223.
    5. Get a heavy 9mm specific buffer it really helps with felt recoil and I run a CMMG bolt in both of mine and they are fine.
    6. If you get a barrell like an adco it can be threaded for 1/2x28. I have a TiRant45 and you can't get the 1/2x36 piston.
    7. Consider a sig brace and save yourself $200 and the longer barrel.

    Signature says he lives in Virginia and as far as I know they have no OAL requirements so he can do what he wants with the barrel length
     

    rouchna

    Defund the ATF
    MDS Supporter
    Nov 25, 2009
    5,951
    Virginia
    Bad news boss.

    1. ATF won't approve less than 29". So, 5 and 7 are out for barrel options.
    2. Get a handguard that will run over the suppressor.
    3. I love my wilson ff tubes. Do you like round or rails.
    4. You are right on with building it. Just like a .223.
    5. Get a heavy 9mm specific buffer it really helps with felt recoil and I run a CMMG bolt in both of mine and they are fine.
    6. If you get a barrell like an adco it can be threaded for 1/2x28. I have a TiRant45 and you can't get the 1/2x36 piston.
    7. Consider a sig brace and save yourself $200 and the longer barrel.


    Signature says he lives in Virginia and as far as I know they have no OAL requirements so he can do what he wants with the barrel length

    Thanks for the info. I'm a VA resident so no issue with OAL. I've done the Sig brace thing and don't care too much for it, so this one is getting a stamp. I planned on getting my barrel from Adco. Now I just need to figure out what rail to go with :thumbsup:
     

    ducrider45

    Active Member
    Jul 29, 2011
    672
    Severn
    You may want to use a Sig-Tac Brace on this build. Keep it as a pistol if you want to go with that short of a barrel. Otherwise your looking at 10+" or longer. ATF will not approve an SBR less than 29" for MD. I just built a dedicated .22LR using a MK4 CMMG .22/9mm upper. I used the brace to avoid the ATF even though it is rimfire (ATF is ignoring the rimfire exclusion) EDIT/ UPDATE: Never mind, I see that you are in VA. This is a 4.5" barrel and a sparrow with a 7.2" hand guard. all .22 not 9mm, but if it helps....... Good luck.


    IMG_20131_zps852c966f.jpg
    [/URL][/IMG]
     

    jkeys

    Active Member
    Jan 30, 2013
    665
    There is very little benefit with going to a 7" barrel in terms of performance. The powder in 9mm ammo is completely burnt within the first 5". It's the reason most hand guns have 3-5" long barrels. With a 7" barrel you will see a very slight velocity gain, but it won't make any noticeable difference unless you are trying to shoot it out to a couple hundred yards.

    I went with a 5" barrel just to keep things short. The only problem I ran into was that I didn't like any of the 4.5" hand guard options that were available. I have a 7" hand guard and my suppressor will fit under it nicely (once I actually get my tax stamp back) so I didn't have to settle for a crappy hand guard.

    Something else worth remembering, 9mm builds are blow back. All of the pressure behind the bullet exerts force on your bolt which slams it into your hammer, hammer pins, bolt catch, etc. A longer barrel increases the dwell time of pressure on the bolt, speeding up it's velocity and increasing the force on the rest of the system. It will be even worse after you add in a suppressor which adds extra back pressure.

    Personally I would plan on a 5" or shorter barrel for shooting suppressed.

    kErV98K.jpg


    Yoau8bx.jpg
     

    dontpanic

    Ultimate Member
    Jul 7, 2013
    6,631
    Timonium
    9mm builds are easiwr than .223 vecause you do not have to deal with the gas block or tube.

    Get a ramped bolt l8ke the Colt or CMMG. This alliws you to use any aftermarket trigger you want. If you use a RRA bolt, you have to use a 9mm hammer.

    I like the handguard covering part of the supressor. I bought the Niveske keymod, but could have easily gobw foe the Midwest Industries. ( I got a great deal on the Noveske )

    The l9nger handguard can be a peoblem with some supressor mounts. Isn't it the AAC where you have to push a buttob to remove it? Anyway that is something to think about.
     

    dontpanic

    Ultimate Member
    Jul 7, 2013
    6,631
    Timonium
    I built my 9mm upper last night. 10.5" barrel with an 11" rail. Still has some tweaking to do, but overall it came our well. J7st need a trigger to finish my build.

    It will be a pistol w/brace that I will eventually SBR.
     

    Attachments

    • 20141109_210313.jpg
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    dontpanic

    Ultimate Member
    Jul 7, 2013
    6,631
    Timonium
    I keep remembering stuff. My barrel is threaded 5/8 x 24. I had to use a thread adapter for this. This allows me to use a .30 caliber supressor.
    This will be my first and I can use it on this rifle, my .308 and for my .223 ARs.
     

    jkeys

    Active Member
    Jan 30, 2013
    665
    9mm builds are easiwr than .223 vecause you do not have to deal with the gas block or tube.

    Get a ramped bolt l8ke the Colt or CMMG. This alliws you to use any aftermarket trigger you want. If you use a RRA bolt, you have to use a 9mm hammer.

    I like the handguard covering part of the supressor. I bought the Niveske keymod, but could have easily gobw foe the Midwest Industries. ( I got a great deal on the Noveske )

    The l9nger handguard can be a peoblem with some supressor mounts. Isn't it the AAC where you have to push a buttob to remove it? Anyway that is something to think about.

    Be careful, most but not all triggers work with the CMMG or similar ramped bolts. The Geissele SD3G will not work for example ( confirmed by Geissele).
     

    dontpanic

    Ultimate Member
    Jul 7, 2013
    6,631
    Timonium
    Be careful, most but not all triggers work with the CMMG or similar ramped bolts. The Geissele SD3G will not work for example ( confirmed by Geissele).


    Thanks. I had heard about some issues like this. That's why I have not bought my trigger yet.

    It was down to CMC with a straight trigger or a Geissele 3 gun. CMC it is. Also costs $100 less.

    By the way, the pistol you posted a couple months ago was the inspiration for my build. So double thanks.
     

    rouchna

    Defund the ATF
    MDS Supporter
    Nov 25, 2009
    5,951
    Virginia
    You may want to use a Sig-Tac Brace on this build. Keep it as a pistol if you want to go with that short of a barrel. Otherwise your looking at 10+" or longer. ATF will not approve an SBR less than 29" for MD. I just built a dedicated .22LR using a MK4 CMMG .22/9mm upper. I used the brace to avoid the ATF even though it is rimfire (ATF is ignoring the rimfire exclusion) EDIT/ UPDATE: Never mind, I see that you are in VA. This is a 4.5" barrel and a sparrow with a 7.2" hand guard. all .22 not 9mm, but if it helps....... Good luck.


    IMG_20131_zps852c966f.jpg
    [/URL][/IMG]

    :D

    Thanks. Nice build.

    There is very little benefit with going to a 7" barrel in terms of performance. The powder in 9mm ammo is completely burnt within the first 5". It's the reason most hand guns have 3-5" long barrels. With a 7" barrel you will see a very slight velocity gain, but it won't make any noticeable difference unless you are trying to shoot it out to a couple hundred yards.

    I went with a 5" barrel just to keep things short. The only problem I ran into was that I didn't like any of the 4.5" hand guard options that were available. I have a 7" hand guard and my suppressor will fit under it nicely (once I actually get my tax stamp back) so I didn't have to settle for a crappy hand guard.

    Something else worth remembering, 9mm builds are blow back. All of the pressure behind the bullet exerts force on your bolt which slams it into your hammer, hammer pins, bolt catch, etc. A longer barrel increases the dwell time of pressure on the bolt, speeding up it's velocity and increasing the force on the rest of the system. It will be even worse after you add in a suppressor which adds extra back pressure.

    Personally I would plan on a 5" or shorter barrel for shooting suppressed.

    kErV98K.jpg


    Yoau8bx.jpg

    This is great information. Thank you. I too have not been able to find a short rail that I like. I think I may just go with the longer one and make sure the Tirant 9 can fit within the rail.

    9mm builds are easiwr than .223 vecause you do not have to deal with the gas block or tube.

    Get a ramped bolt l8ke the Colt or CMMG. This alliws you to use any aftermarket trigger you want. If you use a RRA bolt, you have to use a 9mm hammer.

    I like the handguard covering part of the supressor. I bought the Niveske keymod, but could have easily gobw foe the Midwest Industries. ( I got a great deal on the Noveske )

    The l9nger handguard can be a peoblem with some supressor mounts. Isn't it the AAC where you have to push a buttob to remove it? Anyway that is something to think about.

    I don't think the Tirant 9 has the quick detach option. I think 7 or 9" rail would work. I just have to make sure I check the diameter of the rail prior to purchasing. Thanks. :thumbsup:

    Be careful, most but not all triggers work with the CMMG or similar ramped bolts. The Geissele SD3G will not work for example ( confirmed by Geissele).

    Good call. I was planning on putting in a Geissele trigger. Need to figure out what bold to get.
     

    FlatsFlite

    Active Member
    Aug 6, 2012
    691
    King George, VA
    I built my 9mm upper last night. 10.5" barrel with an 11" rail. Still has some tweaking to do, but overall it came our well. J7st need a trigger to finish my build.

    It will be a pistol w/brace that I will eventually SBR.

    Double check the legality of that vertical for grip / pistol.
     

    teratos

    My hair is amazing
    MDS Supporter
    Patriot Picket
    Jan 22, 2009
    59,775
    Bel Air
    I have a DDLES lower, same dimensions as your gun. I am running s Geissele SSA-E, and it works fine. I used a Seekins BAR. 5.5" barrel under a 9" rail.

     

    rouchna

    Defund the ATF
    MDS Supporter
    Nov 25, 2009
    5,951
    Virginia
    Pretty much the way I went with my build, but since your going to suppress your gun you will want a shorter barrel. Getting the lower engraved so I will have pics with a stock installed shortly.


    IMG_6380
    by 556 Channel (HD), on Flickr


    IMG_6459
    by 556 Channel (HD), on Flickr

    Build video..



    I was hoping you would chime in :D Your builds are always top notch.
    Thanks for posting the videos as well. :thumbsup:

    I have a DDLES lower, same dimensions as your gun. I am running s Geissele SSA-E, and it works fine. I used a Seekins BAR. 5.5" barrel under a 9" rail.


    Thanks Teratos! The Seekins seems to be the only one that would sleeve the Tirant 9. Yours looks exactly the way I want mine to look. Appreciate the post:thumbsup: What LPK and bolt did you use?
     

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