C7

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-3-?

 X    O
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 |3|4||
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  CEBCE
    b

or:

 X    X
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 |3|4||
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  CEBC
    b

or:

 X    
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 |1||||  3rd fret
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 |||||4
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  CGCEB
      b

Notes:  1  : C
        3  : E
        5  : G
        b7 : Bb

Signalling System 7, or C7 - the collection of voice protocols which carry nearly all modern circuit switched telephony. C7 protocols handle call set up, routing, monitoring and tear down

A Canadian made assault rifle based on the American M16. It is licence-built by Diemaco company of Canada. There is also a C8 and a C7A1

Like the M16A2, the C7 is a direct gas operated weapon, but it has full-auto and single-shot modes instead of the original three-round burst and single-shot modes of the M16A2. Other differences are simplified two-position aperture rear sight with only two settings. Barrel is crome-lined and rifled for SS109 (5.56mm NATO) ammunition.

The C7 was recently adopted by the British special forces. As well, it is used by the Danish and Netherlands armed forces.

The C7 rifle, standard primary arm of the Canadian Forces, is an AR-10 variant derived from the American M16A2, and produced by Diemaco / Colt Canada. It has two primary variants - the fixed-stock C7A1, and the collapsible-stock C7A2, which also features an integrated TriRail system near the front sight for mounting of various rifle accessories. These come standard with the C79 sight system, produced by ELCAN - a Canadian subsidiary of Raytheon - which provides 3.4x magnification with a simple tritium-tipped post and horizontal milbars for ease of ranging. (The C79 sight was originally developed for the C9 LMG, which is a variant on the American M249 Squad Assault Weapon.) 

The C8 rifle may also be considered a C7 derivative, though it traces its origins more closely to the M4A1, and will be discussed in greater detail in its own writeup.