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AR Uppers and Lowers

Peppergun
I am new to the AR rifle so any information you can give would be appreciated.
Can you have a complete ar15 and but a Upper of a different caliber on it without having to change the Lower?
Thanks
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4 comments

Date Votes
  • cpermd
    AR lowers come in 2 sizes

    AR15 is by far the most common and is what you have if you are talking 5.56-.223.

    There is a huge list of calibers that work with that platform.

    The 308 platform is the AR10 and LAR10 setup.
    Much larger and not compatible with the AR15 size receiver.

    The answer to your ? is "YES".

    CP
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  • dfletcher
    In addition to interchangability of many centerfire cartridges on the AR 15 platform, you can also use a dedicated 22 lr (rimfire) upper on an AR 15 size lower. You can pretty easily have a single AR 15 sized upper that handles 22 rimfire, 5.56, 7.62X39 and a big bore (45, 50 caliber) with nothing more than an upper and magazine change.

    The AR 10 and "AR 10 type" sized lowers handle 308, 260 Remington, 243, 7-08 sized cartridges using the same method of switching uppers.

    In general, AR 15 is to an AR 10 as a Remington 700 "short action" is to a Remington 700 "long action".
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  • beantownshootah
    quote:Originally posted by Peppergun

    Can you have a complete ar15 and but a Upper of a different caliber on it without having to change the Lower? -[sic]
    Thanks


    The question is, can you take a complete AR-15 in .223, remove the upper, and then put on a different upper in a different caliber to effectively change your gun into a different caliber and/or configuration?

    Answer: Yes, you can, it takes about 30 seconds, and people do it all the time.

    You just have to make sure the upper is compatible with your lower, though 98% of AR-15 aftermarket uppers and lowers now are "milspec" and will work just fine.

    In *some* cases (eg if you want to run certain pistol caliber cartridges like 9mm luger) you may have to make small alterations to the lower to get the conversion to work.

    Available calibers for the AR-15 platform include:

    .223, .22LR, 7.62x39, 5.45x39, 9mm luger, 40SW, .45ACP, 10mm, .204 Ruger, 6.5 Grendel, .450 Bushmaster, .50BMG (!), and many others.

    If you want to run longer length cartridges, then you generally have to step up to the AR-10 platform, which is similar, but designed for .308 and other longer rifle cartridges.
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  • Riomouse911
    There is even a crossbow upper for an AR-15 lower to go with BTS' list of calibers and options. You can also easily add or change the handguards/grips, optics, sights, stocks, triggers, lasers, handles, slings on and on. It's a very versatile set up.
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