M4 motorway not signed, European route E30 includes most of the M4. The M4 has two sections of smart motorway. The one between junctions 19 (M32) and 20 (M5) north of Bristol has variable speed limits and a part-time hard-shoulder. Completion was in summer 2014. The section between junctions 24 and 29 in Newport has variable speed limits. In 2010 it was announced that a smart motorway would be constructed between junctions 3 and 12, with work starting in Autumn 2018. This will be the longest smart motorway scheme in the United Kingdom, with a length of 51km (32 miles). Work is
M4 autocannon effective. The Soviets did not use the P-39 for tank-busting. Soviet pilots appreciated the M4's reliability but complained of its low rate of fire (three rounds per second) and small magazine size (30 rounds). M4 autocannon The 37 mm Automatic Gun, M4, known as the T9 during development, was a 37 mm (1.46 in) recoil-operated autocannon designed by Browning Arms Company. The weapon, which was built by Colt, entered service in 1942. It was used in the Bell P-39 Airacobra and P-63 Kingcobra. Designed primarily as an anti-aircraft weapon, the gun had a muzzle velocity of and a cyclic rate