Convert 5.56 AR Pistol to 300 Blk

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  • ZBryant63

    Member
    May 23, 2019
    12
    If I have a MD registered 5.56 AR Pistol can I legally install a 300 Blk upper? Where can I find regulations on this? Ty for any help!
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,810
    If I have a MD registered 5.56 AR Pistol can I legally install a 300 Blk upper? Where can I find regulations on this? Ty for any help!

    I would think so. You can change the calibers on Thompson Center pistols.
     

    Bountied

    Ultimate Member
    Apr 6, 2012
    6,878
    Pasadena
    Not saying I did exactly what you are saying but yes. My lower says multi-caliber. I don't see an issue with this.
     

    jrumann59

    DILLIGAF
    MDS Supporter
    Feb 17, 2011
    14,024
    How was it registered 5.56 AR pistol or AR Pistol? That would be splitting hairs considering in MD eyes the part that is the gun is the lower.
     

    Bob A

    όυ φροντισ
    MDS Supporter
    Patriot Picket
    Nov 11, 2009
    30,687
    Usually the lower receiver (officially the "firearm") is listed as "Other", leaving you free to build it into a pistol or rifle.

    Per BATF, if you build it as a rifle first, it must remain as a rifle. If you build it into a pistol, you can convert back and forth.

    Once the lower is registered as "other" or pistol, that's as far as MD goes. I don't think there's an issue with swapping calibers on a registered lower.

    BGOS* is endemic in Maryland.


    *Battered Gun Owner Syndrome. It refers to over-scrupulous paranoia regarding any firearm in the "Free State".
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,810
    AFAIK, the gun was purchased as a pistol. It was bought whole.

    How it was transferred should have no bearing. You can change the barrel/caliber of any handgun as long as the design permits. He should also be able to build it into a rifle or SBR as long as he has the proper paperwork(for the SBR) if he so desired.

    IANAL
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    If this were illegal, it would mean converting a .40 to .357 SIG or 9 mm would also be illegal.

    Or 22 conversion setups.
     

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