{{Infobox weapon | name = FB MSBS Grot 5.56 | image = MSB (standard).png | caption = MSBS Grot assault rifle | type = Assault rifle | service = | wars = 2022 Russian invasion of Ukraine | designer = Adam Gawron, Bartosz Stefaniak, Grzegorz Misiołek, Maciej Sajdak | design_date = 2007 | production_date = 2007–2017 (prototypes)2018–present | number = | spec_label = | length = (MSBS Grot C, stock extended) (MSBS Grot B) | action = Short-stroke gas piston, rotating bolt | image_size = 300 | origin = Poland | is_ranged = Yes | used_by = See Users | manufacturer = FB "Łucznik" Radom | variants = See Variants | weight = (MSBS Grot C) (MSBS Grot B) (MSBS Grot 762N) | part_length = | width = | cartridge = 5.56×45mm NATO7,62x51 mm7.62×39mm | rate = 700–900 rounds/min | velocity = 890 m/s | range = | feed = 30-round detachable STANAG magazines, 60-round casket magazine (5.56×45mm NATO) | sights = Integrated Picatinny rail for various optical sights and Picatinny attachable iron sights }} The FB Radom MSBS Grot (, ) is a modular assault rifle developed and manufactured by FB "Łucznik" Radom. There are two basic variants of the rifle: a conventional layout assault rifle and a bullpup. The MSBS is the first machine carbine fully designed and produced completely in Poland since World War II as well as the largest firearms sale contract taken on by the Polish arms industry since 1989. History The MSBS rifle was in development since 2007 by the Military University of Technology (WAT) in Warsaw with cooperation from the firearms manufacturer FB Radom, and was designed to replace the FB Beryl rifle used by the Polish military since 1997. During initial tests conducted by the Military University of Technology, the MSBS rifle and its counterpart HK416 were subjected to comparative testing of the barrel and hand-guard for overheating during an intensive firing schedule. According to the tests, MSBS yielded the better results of the two rifles despite having a relatively light and longer barrel profile. Additional tests have also shown that MSBS is less susceptible to jamming when using lower quality ammunition or when it is insufficiently maintained, and had a more manageable recoil when fired in full-auto compared to other assault rifles chambered in the 5.56 cartridge, such as FB Beryl, HK416, FN SCAR-L or CZ BREN 2. One of the