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Thread: Knights/LMT/LaRue/Mega Upper Compatibility.

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    Knights/LMT/LaRue/Mega Upper Compatibility.

    I have seen on the internet that a Knights SR-25 upper will fit and swap with a LMT MWS upper and a LaRue OBR Upper? Are they all the same dimensions of uppers and lowers?

    I thought that Knight's had a patent to the upper? Does that not cover the dimensions of the LMT and LaRue stripped upper receiver?

    If Knights does then have a patent, are the dimensions of the stripped upper then property of Knights? How can LMT and LaRue manufacture their receivers?

    There are three classes of 308 uppers that I am aware of

    Armalite

    Knights/LMT/LaRue -All 3 companies use the same dimensions for their upper receivers?

    DPMS


    Other brands.

    It would be great if there could be a list or "Chart" that is constantly updated with the new info for .308 ARs such as the new Ruger offering to determine what patterns the guns are based off of and whether their parts are interchangeable. Thanks everyone for their input.

  2. #2
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    Knight's does not have a patent on the dimensions of their uppers, they just never released the information to other manufacturers. So until the M110 became the standard precision semi auto rifle for the Army most other manuf'ers were using AR10 dimensions because it was easier to acquire that information. With the release of the commercial SR25 on a larger scale other makers were capable of acquiring a rifle commercially in order to obtain the dimensions or worked out some form of deal with KAC to produce/purchase the information. There tends to be two lines of upper and lower compatibility branches that either follow AR10 or SR25/Mk11/M110 dimensions. Until recently the majority of manufacturers followed AR10 but due to military procurment the more common SR25 platform is what more manufacturers are adopting so much that Armalite has changed the dimensions on their newer models to follow SR25 profile in order to potentially compete on future gov't/mil contracts for backwards compatibility. As for which manufacturers uppers and lowers are cross compatible, I unfortunately do not have that list to provide you with. I am certain someone eveuntally will be publishing it in order to try and set themselves up as the "authority" on 30 cal AR semi-auto systems.

  3. #3
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    Armalite on Larue:




    Larue on KAC:



    Larue on KAC, KAC on Larue:



    LMT and KAC lowers are nearly identical.

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    Quote Originally Posted by LAWMENS View Post
    Knight's does not have a patent on the dimensions of their uppers, they just never released the information to other manufacturers. So until the M110 became the standard precision semi auto rifle for the Army most other manufacturers'ers were using AR10 dimensions because it was easier to acquire that information. With the release of the commercial SR25 on a larger scale other makers were capable of acquiring a rifle commercially in order to obtain the dimensions or worked out some form of deal with KAC to produce/purchase the information. There tends to be two lines of upper and lower compatibility branches that either follow AR10 or SR25/Mk11/M110 dimensions. Until recently the majority of manufacturers followed AR10 but due to military procurement the more common SR25 platform is what more manufacturers are adopting so much that Armalite has changed the dimensions on their newer models to follow SR25 profile in order to potentially compete on future gov't/mil contracts for backwards compatibility. As for which manufacturers uppers and lowers are cross compatible, I unfortunately do not have that list to provide you with. I am certain someone eventually will be publishing it in order to try and set themselves up as the "Authority" on 30 cal AR semi-auto systems.
    A small bit of sarcasm directed towards someone who used to be a member here... funny stuff, I caught that immediately. It would be nice to have a chart that more than one SME and manufactures contribute to. It would be ideal if manufactures could post there recommendations of what other components will work with their products, but I'm sure there's liability in there some where.

    Thank you for the info. I appreciate it!

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    Quote Originally Posted by sinister View Post

    LMT and KAC lowers are nearly identical.
    Nice! thanks for the pics, does the Knights or LaRue eat a wider variety of ammo? Im not going to ask which one is more accurate, just which one you know performs better with a wider range of ammo selection. Not meant to derail thread at all. I think most of us are jealous for either, let alone both.

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    Quote Originally Posted by WatersEdge View Post
    Nice! thanks for the pics, does the Knights or LaRue eat a wider variety of ammo? Im not going to ask which one is more accurate, just which one you know performs better with a wider range of ammo selection. Not meant to derail thread at all. I think most of us are jealous for either, let alone both.
    That last pic is one I took when I was at the height of my .308AR fever...

    Based on my experience (just one data point) neither the OBR nor the EMC worked very well with 7.62NATO surplus like DAG bi-metal 150gr, FN 144gr (vintage 1981), etc -- fairly frequent FTE/FTFs. Magtech 150gr was OK, and both REALLY liked the Hornady TAP 168gr loads.

    ETA: The AR10 upper in the first photo may fit correctly onto a KAC/LaRue/LMT lower, but you can't insert a magazine unless you cut away the two tabs that make the upper compatible with Armalite's M14-based steel magazines. Unless, of course, that Armalite upper is off an AR10A (uses Magpul LR20s) -- in which case you're fine.
    Last edited by caporider; 11-20-13 at 17:06.
    Scout Rider for the Mongol Hordes

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    I've tried swapping uppers and lowers on a few. The KAC and LMT swaps went well. Either with Larue looked real close, but it would've taken more force to put together than what I was comfortable with.

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    Quote Originally Posted by LAWMENS View Post
    I am certain someone eveuntally will be publishing it in order to try and set themselves up as the "authority" on 30 cal AR semi-auto systems.
    Quote Originally Posted by WatersEdge View Post
    A small bit of sarcasm directed towards someone who used to be a member here... funny stuff, I caught that immediately. It would be nice to have a chart that more than one SME and manufactures contribute to. It would be ideal if manufactures could post there recommendations of what other components will work with their products, but I'm sure there's liability in there some where.

    Thank you for the info. I appreciate it!
    Yikes. I'm not sure that was directed at the person you think!
    Last edited by CharlieMike; 11-23-13 at 08:49.
    Disclosure: I'm a dealer/owner of an online firearms accessories store.

  9. #9
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    KAC, Armalite (A model), Ruger , Matrix , Genesis , LaRue, LMT and by the looks of things Core. All use the same pattern. Only issue you might have is pin size when swapping uppers. LMT and KAC use .281 pin sizes. Armalite , Matrix , Genesis will use .277 pin .

    On a side note, Mega uses the same cut but might not fit many lowers, as they are so tight on their spec you would might have to mod the upper and it doesn't fit cosmetically either.

    http://www.ar15.com/forums/t_3_121/6...80__Build.html

    Quote Originally Posted by WatersEdge View Post
    I have seen on the internet that a Knights SR-25 upper will fit and swap with a LMT MWS upper and a LaRue OBR Upper? Are they all the same dimensions of uppers and lowers?

    I thought that Knight's had a patent to the upper? Does that not cover the dimensions of the LMT and LaRue stripped upper receiver?

    If Knights does then have a patent, are the dimensions of the stripped upper then property of Knights? How can LMT and LaRue manufacture their receivers?

    There are three classes of 308 uppers that I am aware of

    Armalite

    Knights/LMT/LaRue -All 3 companies use the same dimensions for their upper receivers?

    DPMS


    Other brands.

    It would be great if there could be a list or "Chart" that is constantly updated with the new info for .308 ARs such as the new Ruger offering to determine what patterns the guns are based off of and whether their parts are interchangeable. Thanks everyone for their input.
    Last edited by kalieracer; 11-24-13 at 14:21.

  10. #10
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    Here is a video of 80% Genesis lower I built with a Mega upper, the lower now has a modified AR-10b upper that was converted to run SR-25 / Pmags


    http://www.youtube.com/watch?v=PXze1wB-vxw

  11. #11
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    KAC / LMT are the same lower forgings. The Larue is billet, and might have a bit tighter tolerance , you would need to file down the upper in the rear and the pin size might also be different.

    Quote Originally Posted by tom12.7 View Post
    I've tried swapping uppers and lowers on a few. The KAC and LMT swaps went well. Either with Larue looked real close, but it would've taken more force to put together than what I was comfortable with.

  12. #12
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    Quote Originally Posted by sinister View Post
    Armalite on Larue:



    Larue on KAC:



    Larue on KAC, KAC on Larue:



    LMT and KAC lowers are nearly identical.
    unlikely bedfellows.

  13. #13
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    We can add Les Baer' 308 upper to the list too.

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