Sig 556, 556R

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  • Cyclone

    Jr. Zombie Killer
    Jan 25, 2010
    835
    Rosedale, MD
    What's the difference between a 551 and a 556?

    ...* the 556 / 551 barrel does not interchange...the rear is treaded differently...likewise the treading for a muzzle attachment differs...

    ...* the swiss lower will fit and function with the 556 upper...however...when attaching a 556 lower to a swiss upper a small amount of metal must be relieved from the lower portion of the trunion to accomadate the Nato STANAG magazines...

    ...* the swiss folding stock will not interchange with the collapsing stock...

    ...* the magazine catch assembly in the 551 differs from that in the 556...and will not interchange...

    ...* the magazines do not interchange...
     
    Feb 28, 2013
    28,953
    ...* the 556 / 551 barrel does not interchange...the rear is treaded differently...likewise the treading for a muzzle attachment differs...

    ...* the swiss lower will fit and function with the 556 upper...however...when attaching a 556 lower to a swiss upper a small amount of metal must be relieved from the lower portion of the trunion to accomadate the Nato STANAG magazines...

    ...* the swiss folding stock will not interchange with the collapsing stock...

    ...* the magazine catch assembly in the 551 differs from that in the 556...and will not interchange...

    ...* the magazines do not interchange...

    What about the issue here lately with the MSP deciding to treat the 556 as a copy of the regulated version for some reason?
     

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