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Thread: AR10/.308 AR Build knowledge thread.

  1. #131
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    I'm getting into the .308 AR game. I started with a new, complete CMMG Mk.3 lower I picked up at a good price. Having now found this thread, am finding my new lower a bit odd as this link ( https://docs.google.com/spreadsheets...en&output=html) shows I will need a DPMS pattern upper, but the SR25 type mags. Can anyone verify this before I spring for some mags? I have no preference, I just want what will work.
    Last edited by daddyusmaximus; 09-22-15 at 15:34.
    You know what I like best about most people?

    Their dogs.

  2. #132
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    Quote Originally Posted by daddyusmaximus View Post
    I'm getting into the .308 AR game. I started with a new, complete CMMG Mk.3 lower I picked up at a good price. Having now found this thread, am finding my new lower a bit odd as this link ( https://docs.google.com/spreadsheets...en&output=html) shows I will need a DPMS pattern upper, but the SR25 type mags. Can anyone verify this before I spring for some mags? I have no preference, I just want what will work.
    DPMS and SR25 are the same thing.

  3. #133
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    I returned my PSA upper because it just would not work, I even tried 2 other BCGs. To PSA's credit they did let me return it for a refund after 6 months. I would have preferred to have it work though. I am shopping for another upper, just not sure what I can trust.

  4. #134
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    With 308s it is best to buy the upper and lower from the same company. There are subtle variations between different LR308 (DPMS) compatible components. On the 7 builds I have done I went with 6 Aero Precision, 1 PSA. The PSA stuff definitely only works with PSA. The biggest variation I have noticed is Takedown and Pivot pin lengths and Bolt Catches. I also matched LPKs to lower manufacturers to minimize compatibility issues.

    Sent from my SCH-I535 using Tapatalk

  5. #135
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    Quote Originally Posted by SpookyEng View Post
    With 308s it is best to buy the upper and lower from the same company. There are subtle variations between different LR308 (DPMS) compatible components. On the 7 builds I have done I went with 6 Aero Precision, 1 PSA. The PSA stuff definitely only works with PSA. The biggest variation I have noticed is Takedown and Pivot pin lengths and Bolt Catches. I also matched LPKs to lower manufacturers to minimize compatibility issues.

    Sent from my SCH-I535 using Tapatalk

    ^this

    I went with matching upper/lower as a result of reading about these problems, which are less likely to happen with an AR-15. The fact there is no TDP for .308 means this problem is unlikely to go away any time soon

  6. #136
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    Quote Originally Posted by Bang4Buck View Post
    ^this

    I went with matching upper/lower as a result of reading about these problems, which are less likely to happen with an AR-15. The fact there is no TDP for .308 means this problem is unlikely to go away any time soon
    Agreed, which is frustrating really considering that you have to find some way to force companies to stick to a standard. Wish they'd put aside their ego's and try to go for a standard.

  7. #137
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    Quote Originally Posted by daddyusmaximus View Post
    I'm getting into the .308 AR game. I started with a new, complete CMMG Mk.3 lower I picked up at a good price. Having now found this thread, am finding my new lower a bit odd as this link ( https://docs.google.com/spreadsheets...en&output=html) shows I will need a DPMS pattern upper, but the SR25 type mags. Can anyone verify this before I spring for some mags? I have no preference, I just want what will work.
    That spreadsheet has so many errors with it, where to begin...

  8. #138
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    Quote Originally Posted by Valintina View Post
    Agreed, which is frustrating really considering that you have to find some way to force companies to stick to a standard. Wish they'd put aside their ego's and try to go for a standard.
    What about the companies that deviated from their original receiver designs? There are several that have done that, most of them actually.

    There is no standard. This was even going on with the original Fairchild ArmaLite back in the 1950's. After the input they received from people around the world during the demonstrations, they accepted that everyone wanted the rifle to be a little smaller. ArmaLite redesigned the AR10 into what was called the AR10A and had a prototype by 1959 when the Stoner patents were sold to Colt. It became the Colt AR10A, and Colt tooled up to manufacture it, building a $100k assembly line. The AR10A had the fire control group of the AR15, smaller receiver length, redesigned gas key, roller cam pin, and a different charge handle.

    After more rifle demos, numerous nations were ready to make orders for the AR15, even though they liked the AR10. Colt shut down their plans to build the AR10A, and began cranking out the Colt Model RO601 AR15 military rifle in 5.56x45.

    Fast forward to the late 1980's, and Gene Stoner working with Reed Knight II on a new 7.62 NATO AR using as many components of the AR15 as possible, in order to reduce any additional tooling or vendor costs for production, and thus was born the SR25.

    Eagle Arms saw the market opportunity, and made the EA-10/AR-10, and acquired the ArmaLite name from Elsico Tool and Machine in the Philippines (kinda convoluted story how it ended up there, but it did). Eagle/ArmaLite Inc. probably didn't want to face any intellectual property suits on the AR10, so they made changes to some of the aspects of the gun, even though they used an SR25 upper for the testing and proof work on the "AR10". Since it was designed right at the onset of the Clinton AWB, they couldn't manufacture new 20rd mags for it, so they built the lower around available surplus mags on the market, betting on customers wanting more than 10rd capacity options.

    Then DPMS jumped on the bandwagon, using a different receiver design with the LR-308, but SR25 magazine compatibility, first with a really bad polymer 10rd mag that the BCG would remove material from the first several cycles.

    DPMS has at least 3 different rail heights for the LR-308 and AP4. The first was really high, so you could use scope rings from most bolt guns, without needing a special riser or AR mount. Then the AP4 had a lower height, and then another change was made to make the height different again, to match other receivers on the market like the SR25 height.

    Several years ago, ArmaLite Inc. answered consumer demand to offer an AR10 that was SR25 mag compatible, and introduced what they call the AR10A (not to be confused with the original of 1959-a totally different gun).

    Then DPMS introduced the GII, which is entirely a different animal. Different BCG, different receivers, different extensions, different ejection port cover. Adams Arms is the first company to make a GII compatible rifle, but with the op-rod system instead of internal gas expansion.

    There is no standard, and it benefits rifle makers to keep control of what they are doing in house because of all the problems associated with people putting in garbage parts into their parts, then posting online how brand X sucks, when the parts causing the problem came from brand G for garbage.

  9. #139
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    Quote Originally Posted by LRRPF52 View Post
    SNIP.
    Wow, thanks for the History lesson!

    Never thought that Eagle Arms started the damn process. What happened to them?

  10. #140
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    Quote Originally Posted by Valintina View Post
    Wow, thanks for the History lesson!

    Never thought that Eagle Arms started the damn process. What happened to them?
    They changed their name to ArmaLite Inc., and ArmaLite Inc. still retains the Eagle Arms brand as their economy line.

    My first AR10 was actually an EA10T 24" bull chromoly barrel with a knurled aluminum handguard. The gun shot 1/3 MOA, it was point and click. For those of us that were around in the 1980's, some will remember Eagle Arms and their EA15's with the Coal Valley Illinois markings. In the early-to-mid 1990's, Mark Westrom acquired the ArmaLite name and consolidated under that.

    Independent of Armalite, Karl Lewis and Jim Glazier formed a company named Eagle Arms in Coal Valley Illinois in 1986. Eagle Arms initially marketed M16 and AR-15 type rifle parts. The early Stoner patents had expired, and Eagle was able to build both parts and complete rifles. In 1989, Eagle commenced production of complete rifles, with LMT serving as the major supplier.
    ArmaLite Inc. has a history section on their website if you want to track the ArmaLite name and all it has been through. With the recent acquisition by SAC and web redesign, I see they have removed reference to using the SR25 in the prototype process of developing the AR10B in 1996. There is now a gap between 1990 and 1998 that was not present on the old ArmaLite Inc. website. https://armalite.com/about-us/history/
    Last edited by LRRPF52; 11-07-15 at 11:09.

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