ar-9 barrel length vs handguard

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  • davsco

    Ultimate Member
    Oct 21, 2010
    8,607
    Loudoun, VA
    hi, i want to sbr a pcc. i'm looking at an odin 7.5" 9mm barrel, in an aero slick sided ar-15 upper receiver, with an aero atlas 7" handguard. i haven't selected it but will also have a comp on the barrel. see any issues?
     

    RuralRifleGuy

    Active Member
    Aug 16, 2018
    918
    Queenstown
    As long as none of the ports are inside the handguard it should be fine.

    I run a 10.5" 300 blackout barrel inside a 12" ATLAS handguard with a Noveske KX3 Flash Suppressor, I would never run any muzzle device with ports inside a handguard. Too easy to have your hand over the ports and you risk damaging the handguard.
     

    IX-3

    Active Member
    Aug 21, 2018
    424
    Eastern Shore, MD
    Here is my 10.5” 9MM with a 9” ATLAS S-One handguard and a VG6 Precision GAMMA 9MM. With a 7.5” barrel measuring closer to 7” installed and the ATLAS 7” actually being 7.25” you may be pretty close to the handguard with a muzzle device. I’d get everything but the muzzle device and see how much room you have to work with so you don’t spend a bunch of money on something that’s going to end up blasting the handguard.
     

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    davsco

    Ultimate Member
    Oct 21, 2010
    8,607
    Loudoun, VA
    that's what i'm trying to figure out, the acceptable geometry. rrg is saying his 10.5 barrel works inside a 12 handguard. but ix is saying his 10.5 barrel works inside a 9 handguard. those seem a little contradictory, but perhaps depends on the comp and how far out the ports start. looking at ix's gun, i'd say the handguard to barrel relationship looks pretty good. maybe i should be looking at an 8-8.5" barrel.
     

    RuralRifleGuy

    Active Member
    Aug 16, 2018
    918
    Queenstown
    that's what i'm trying to figure out, the acceptable geometry. rrg is saying his 10.5 barrel works inside a 12 handguard. but ix is saying his 10.5 barrel works inside a 9 handguard. those seem a little contradictory, but perhaps depends on the comp and how far out the ports start. looking at ix's gun, i'd say the handguard to barrel relationship looks pretty good. maybe i should be looking at an 8-8.5" barrel.

    To clarify mine is a flash suppressor that shoves everything out the front, it has no ports inside the handguard, I wouldn't run anything where ports are inside the handguard. I've attached a photo of what I'm running and it sticks out about a 1/4" past the end of the handguard.
     

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    RuralRifleGuy

    Active Member
    Aug 16, 2018
    918
    Queenstown
    This is my other 300 Blackout pistol, it's a 7.5" barrel in a 7" ATLAS handguard, it has a mini flash can on it, but could easily run something similar to what IX-3 has on his 9mm because none of the ports would be within the handguard. If you look in the last few holes on my handguard you can see where the barrel and muzzle device meet.

    Edit: When I get home I can get a photo of both handguards and how the muzzle devices appear on both. I might be able to pop on a compensator so you can see what that looks like as well, if I have one.
     

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    IX-3

    Active Member
    Aug 21, 2018
    424
    Eastern Shore, MD
    that's what i'm trying to figure out, the acceptable geometry. rrg is saying his 10.5 barrel works inside a 12 handguard. but ix is saying his 10.5 barrel works inside a 9 handguard. those seem a little contradictory, but perhaps depends on the comp and how far out the ports start. looking at ix's gun, i'd say the handguard to barrel relationship looks pretty good. maybe i should be looking at an 8-8.5" barrel.

    His 10.5 with a 12 handguard is a 300 blackout so he has more of the 10.5" of barrel coming out of his receiver. Mine is a 9MM and they are usually .5" shorter overall compared to 5.56 barrels of the same length. The 9mm barrels don't have a chamber for the bolt to lockup into so a 10.5" 9mm barrel might only have 10" outside of the receiver.

    Here is an example (not a great photo) of my 10.5" 9MM vs my 10.5" 5.56. Both have Aero uppers and 9" ATLAS S-One handguards. The only difference is the 9MM has the GAMMA muzzle brake and the 5.56 has a standard flash hider. You can see more of the 5.56 barrel (top) sticking out from the handguard vs the 9mm (bottom).

    An 8-8.5" barrel with a 7" ATLAS will look similar to my 9mm.
     

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    davsco

    Ultimate Member
    Oct 21, 2010
    8,607
    Loudoun, VA
    ok from the looks of both ix and rrg's 9mm's, it looks like having the nominal barrel length 1.5" > atlas handguard nominal length gives enough room without too much room. so with my 7" atlas that's telling me i should be looking for 8-8.5" 9mm barrel. and super thanks to both of you for the pics, that really helps put this in perspective!

    i don't want the comp gas hitting me (or the handguard) but also don't want the barrel unnecessarily long.
     

    danb

    dont be a dumbass
    Feb 24, 2013
    22,704
    google is your friend, I am not.
    Only comment I have is SBR needs to have 29" OAL (excluding muzzle device, unless its pinned). 8.5" barrel is probably too short. It is for my set up. 7 or 8" barrel works on a pistol (with a brace) because it does not need to comply with stupid MD Copycat rifle rules.
     

    IX-3

    Active Member
    Aug 21, 2018
    424
    Eastern Shore, MD
    Only comment I have is SBR needs to have 29" OAL (excluding muzzle device, unless its pinned). 8.5" barrel is probably too short. It is for my set up. 7 or 8" barrel works on a pistol (with a brace) because it does not need to comply with stupid MD Copycat rifle rules.

    He's in VA so he doesn't have to play by our stupid rules.

    My 10.5" is 28.75" based on measurements against my 16" AR so I will have to go with a Magpul ACS stock to make the 29" mark.
     

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    So, to figure out actual barrel length/handguard length/muzzle device length there are differences between a 9mm that usually lacks a barrel extension, or a dedicated 22 that actually extends the chamber face into the receiver. Basically a standard DI barrel with extension has a chamber that ends up near flush with the front face of the top rail in the upper, and about .6" long muzzle threads, so a handguard that equals the barrel length will be about flush with the muzzle, and the body of a muzzle device will be up to .6" inset. Of course any brakes that angle gas back might need a little extra clearance, linear comps can basically exit flush with the end of the handguard, but also include the barrel thread length, so a 10" barrel with 6" linear comp and .1" shim/washer will end up 15.5" long. A 9mm barrel basically replaces the barrel extension with the chamber, moving about .5" back inside the upper, so about .5" less barrel will be out front for a handguard to cover. Dedicated 22 barrels in CMMG pattern have the chamber extended about 1.4" into the upper, but only .4" long muzzle threads, so you will need to add 1.3" to hanguard to meet the muzzle in the same place as a DI barrel, or add .5" to meet a 9mm barrel in the same place as a DI barrel.

    so TLDR: a 7" handguard will be about flush with the muzzle on a 7.5" 9mm barrel, being it's a 9mm, thats OK with a bare muzzle or small 3 lug adapter/linear comp, with a comp, you aren't going to have much clearance , and might get some gas hitting the handguard if the port is right at the muzzle and angled back.
     

    Ammo Jon

    Ultimate Member
    Mar 3, 2008
    20,785
    7.5” 556/7” handguard
     

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    rockstarr

    Major Deplorable
    Feb 25, 2013
    4,592
    The Bolshevik Lands
    Here is my 10.5” 9MM with a 9” ATLAS S-One handguard and a VG6 Precision GAMMA 9MM. With a 7.5” barrel measuring closer to 7” installed and the ATLAS 7” actually being 7.25” you may be pretty close to the handguard with a muzzle device. I’d get everything but the muzzle device and see how much room you have to work with so you don’t spend a bunch of money on something that’s going to end up blasting the handguard.

    whats a good price for one of these ? Im thinking about adding one to my grand power Stribog until i can get a suppressor for it.

    Are you pleased with yours ?
     

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