The MAC-10 (Military Armament Corporation Model 10, officially the M-10) is a highly compact, blowback operated machine pistol developed by Gordon B. Ingram in 1964.
The M-10 was built predominantly from steel stampings. A notched cocking handle protrudes from the top of the receiver, and by turning the handle 90° would lock the bolt, and act as an indicator that the weapon is unable to fire. The M-10 has a telescoping bolt, which wraps around the barrel. This allows a more compact weapon, and balances the weight of the weapon over the pistol grip where the magazine is located. The M-10 fires from an open bolt, and in addition, the light weight of the bolt results in a rapid rate of fire. The barrel is threaded to accept a suppressor, which worked by reducing the discharge's sound, without attempting to reduce the velocity of the bullet. At the suggestion of the United States Army, Ingram added a small bracket with a small strap beneath the muzzle to aid in controlling recoil during fully automatic fire.
The primary reason for the original M-10 finding recognition was its revolutionary sound suppressor designed by Mitchell Werbell III of Sionics. This suppressor had a two-stage design, with the first stage being larger than the second. This uniquely shaped suppressor gave the MAC-10 a very distinctive look. It was also very quiet, to the point that the bolt could be heard cycling, along with the suppressed report of the weapon's discharge. Later-production variants had a "wipeless" suppressor front cap design that was advanced for the time in that its internal metal parts needed only to be cleaned, not replaced, in contrast to the older-technology "wipe" type suppressors. The suppressor also created a place to hold the weapon; this, combined with the weight it added, made the weapon easier to control.

en.wikipedia.org/wiki/MAC-10
MAC 10 and MAC 11

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