Patent ID: 8464625

Claim:
A barrel-mounted device in combination with a firearm comprising: a unit for joining to the barrel, a casing and a starting part with gas vents, and wherein a starting part bore is the continuation of the barrel/gun bore and there are N≧1 compartments between the casing and the starting part, wherein each compartment includes at least two gas vents and is adapted to ensure gas exhaust from the starting part bore to at least one of the compartments through the first of the mentioned gas vents and gas exhaust from the compartment to the starting part bore through the second gas vent; moreover, the compartment length is 0.5-3.0 of a bore caliber and in every cross-section plane of the barrel-mounted device intersecting at least one compartment the following condition is met: 0.4 ⁢ S K ≤ ∑ i = 1 M ⁢ ⁢ S i ≤ 4.5 ⁢ S K where: S K —is the area of the bore; S i —is the minimal area of the i-th compartment intended for the gas flow between gas vents; M —is the number of compartments in the mentioned cross-section plane, 1≦M≦N.