The MA-75B Assault Rifle/Grenade Launcher (and its predecessor, the M.75) is a .32 caliber assault rifle-grenade launcher combo. Its primary fire is automatic, but it can be assumed that there is a semi-automatic setting because Leela talks about inaccuracy on the fully automatic setting. The rifle's secondary fire fires a 20 mm anti-personnel grenade.
The rifle's integrated grenade launcher is essential for those wishing to "grenade jump" to otherwise unreachable ledges within the games.
The M.75 and MA-75B can only be operated in atmosphere. Neither will work in vacuum nor in fluid.
Fires 600 rounds per minute of .75 caliber shells. Standard clip holds 52 rounds of high velocity ammunition. Also fires M-class ultra-high yield grenade cartridges. Grenade clips hold 7 rounds. M .75 ammunition is neither vacuum enabled nor teflon coated, and due to a manufacturing defect is highly inaccurate at long range.
- from Marathon manual
When firing on the fully automatic setting this weapon is highly inaccurate, but the grenades hit hard and it's the best we can do right now. Ammunition may be scarce for a while, so be prepared to fall back to your pistol.
- Leela, from Marathon, Bigger Guns Nearby, second terminal
The original M. 75 was a ridiculous toy designed to impress aging pompous generals. Gone are the preposterously short barrel and the prodigious recoil that made firing the weapon akin to wrestling a greased pig. Still here is the oxygen hungry ammunition that makes it impossible to fire in vacuum.
- from Marathon 2 manual
- Leela twice references the M.75 as the "AR-75."
- An early Marathon beta gives the assault rifle the designation "M.2C".
- It would share the same beginning two letters in its designation as four guns in the Halo game series, all of which are also assault rifles (the MA37 ICWS, the MA5B ICWS, the MA5C ICWS, and the MA5D ICWS); however, all four guns would be without underslung attachments of any sort save for perhaps a flashlight.