The 76 mm mountain gun M1958 (M-99, GP or 2A2) was a Soviet mountain gun designed during the 1950s.
Developed by SKB-172 under the guidance of Mikhail Yurievich Tsirulnikov. The M-99 passed factory tests in December 1954 and passed military tests on 21 April 1955.
The M-99 was officially adopted in 1958 under the name 76 mm GP mountain gun. At this time, a new indexing of guns was introduced, and the M-99 received the GRAU index number 2A2.
The barrel is the same as the 76 mm mountain gun model 1938. It has a split-trail carriage, a hydro-pneumatic recoil mechanism, a semi-automatic horizontal sliding wedge breech, torsion bar suspension, and pneumatic tires for motor transport. The gun is collapsible or can be broken down into 10 pack loads for transport.