Discussion of how to get an 8.5" Barrel SBR AR15 to 29" OAL

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  • j_h_smith

    Ultimate Member
    Jul 28, 2007
    28,516
    Take off the removable muzzle attachment for proper measurement. Once I removed mine, there was more length than I thought.
    Don't assume what length is under the muzzle device.

    I took off the muzzle brake and put everything together again. 28 5/8" overall length. I measured my barrel by putting a dowel down the barrel until it hit the bolt face. The barrel is 8 5/8".

    I just can't see how you're getting 29 1/16 from just about the same setup. Could you measure your barrel the same way I did? I don't know why I'm more than 3/8" too short. This just doesn't make since.

    I'm just about ready to throw away the 8 1/2" barrel and install the 10 1/2 " barrel.

    I feel like that guy in the insurance commercial. The one where the kid gets a new car and he finds his car up on blocks.

    This SUCKS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    I don't like losing. I want to make this work.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,818
    I took off the muzzle brake and put everything together again. 28 5/8" overall length. I measured my barrel by putting a dowel down the barrel until it hit the bolt face. The barrel is 8 5/8".

    I just can't see how you're getting 29 1/16 from just about the same setup. Could you measure your barrel the same way I did? I don't know why I'm more than 3/8" too short. This just doesn't make since.

    I'm just about ready to throw away the 8 1/2" barrel and install the 10 1/2 " barrel.

    I feel like that guy in the insurance commercial. The one where the kid gets a new car and he finds his car up on blocks.

    This SUCKS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    I don't like losing. I want to make this work.

    Barrel length isn't the point here. Overall length is. Have you considered a Vltor A-5 stock. They're known to make 29" on SBRs with 8.5" barrels. LOP is 16.25" fully extended.
     

    j_h_smith

    Ultimate Member
    Jul 28, 2007
    28,516
    Barrel length isn't the point here. Overall length is. Have you considered a Vltor A-5 stock. They're known to make 29" on SBRs with 8.5" barrels. LOP is 16.25" fully extended.

    Ya need to go back and read some of the conversation. We've been comparing builds with different ideas passed between a few of us. The latest was to use the A5 buffer tube along with the Magpul ACS-L stock and .70" butt pad. Bought the butt stock and pad, hoping to get to that magic number, but I'm still only at 28.5". Since I have the same parts that others have (as far as we know), I wanted to make sure the others actually had an 8.5" barrel. I've got a 9.5" 300blk upper and of course I've made the 29" easy. That upper will be shared with my 5.56 SBR lower.

    8.5" barrel, 9mm upper receiver, A5 buffer tube, Magpul ACS-L butt stock (longer than the VLTOR stock) and Magpul .70" pad. Others have gotten to the 29" length with the same equipment and I'm just a shade over 28.5"

    I've been working on this SBR for a few months trying to get to that >29" length. Still no luck!
     
    I took off the muzzle brake and put everything together again. 28 5/8" overall length. I measured my barrel by putting a dowel down the barrel until it hit the bolt face. The barrel is 8 5/8".

    I just can't see how you're getting 29 1/16 from just about the same setup. Could you measure your barrel the same way I did? I don't know why I'm more than 3/8" too short. This just doesn't make since.

    I'm just about ready to throw away the 8 1/2" barrel and install the 10 1/2 " barrel.

    I feel like that guy in the insurance commercial. The one where the kid gets a new car and he finds his car up on blocks.

    This SUCKS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    I don't like losing. I want to make this work.

    I just measured for you...
    A cleaning rod w/sharpie mark bottomed out at 8-5/8"
    My commercial buffer tube extends 7-3/8" past the receiver itself- with the tube just kissing the buffer retainer pin. This might be where you're losing. I know commercial tubes are longer than milspec, but I don't know by how much.
    Everything is PSA and I bought the 8.5" compete upper from them already assembled.
    Without being condescending- did you measure with the buttstock on a table/vertical and put a tape measure or yardstick behind it?
    I also can't see how our measurements are that far apart. I would understand 1/4", even 3/8", but not a 1/2" discrepancy.

    *Please Note*- My legal length is with the ACS-L as shipped and the .70" extension (tabs broken off) bolted on top of the as-shipped pad (Home Depot 1" hex bolts). I fell short by removing the factory pad and adding the .70" pad. I mentioned wanting to do this in a previous post and highlighted it on post #80- sorry I wasn't clear about that..
    It isn't pretty, but it is legal.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,818
    Ya need to go back and read some of the conversation. We've been comparing builds with different ideas passed between a few of us. The latest was to use the A5 buffer tube along with the Magpul ACS-L stock and .70" butt pad. Bought the butt stock and pad, hoping to get to that magic number, but I'm still only at 28.5". Since I have the same parts that others have (as far as we know), I wanted to make sure the others actually had an 8.5" barrel. I've got a 9.5" 300blk upper and of course I've made the 29" easy. That upper will be shared with my 5.56 SBR lower.

    8.5" barrel, 9mm upper receiver, A5 buffer tube, Magpul ACS-L butt stock (longer than the VLTOR stock) and Magpul .70" pad. Others have gotten to the 29" length with the same equipment and I'm just a shade over 28.5"

    I've been working on this SBR for a few months trying to get to that >29" length. Still no luck!
    My bad

    Sent from my XT1585 using Tapatalk
     

    j_h_smith

    Ultimate Member
    Jul 28, 2007
    28,516
    I just measured for you...
    A cleaning rod w/sharpie mark bottomed out at 8-5/8"

    Check, exactly the same

    My commercial buffer tube extends 7-3/8" past the receiver itself- with the tube just kissing the buffer retainer pin. This might be where you're losing. I know commercial tubes are longer than milspec, but I don't know by how much.

    Check, exactly the same

    Everything is PSA and I bought the 8.5" compete upper from them already assembled.

    Built mine from scratch, but I can't see my receiver being 1/2" shorter than yours. As a matter of fact, I have measured this upper and it compares to every other one I own.

    Without being condescending- did you measure with the buttstock on a table/vertical and put a tape measure or yardstick behind it?

    Yes, I used 3 different rules/rulers and they are all within 1/32 of each other.

    I also can't see how our measurements are that far apart. I would understand 1/4", even 3/8", but not a 1/2" discrepancy.

    That's why it's bugging me so much. I can see 1/16, maybe an 1/8 and at an all time WOW difference of 1/4", but not 1/2".


    *Please Note*- My legal length is with the ACS-L as shipped and the .70" extension (tabs broken off) bolted on top of the as-shipped pad (Home Depot 1" hex bolts). I fell short by removing the factory pad and adding the .70" pad. I mentioned wanting to do this in a previous post and highlighted it on post #80- sorry I wasn't clear about that..
    It isn't pretty, but it is legal.

    That would account for no more than 1/4", which still leaves me 1/4" short. I don't know, I'm not wanting to have a 1/2" spacer milled for the buttplate, so I may just go with a short muzzle brake and solder it on. I can still get the rail off if I need to. I've ran out of ideas. I just know.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,818
    Check, exactly the same



    Check, exactly the same



    Built mine from scratch, but I can't see my receiver being 1/2" shorter than yours. As a matter of fact, I have measured this upper and it compares to every other one I own.



    Yes, I used 3 different rules/rulers and they are all within 1/32 of each other.



    That's why it's bugging me so much. I can see 1/16, maybe an 1/8 and at an all time WOW difference of 1/4", but not 1/2".




    That would account for no more than 1/4", which still leaves me 1/4" short. I don't know, I'm not wanting to have a 1/2" spacer milled for the buttplate, so I may just go with a short muzzle brake and solder it on. I can still get the rail off if I need to. I've ran out of ideas. I just know.
    Jim, I know you don't do pictures, but a couple might be a big help.
     

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