The MSBS Grot (, ) is a family of modular assault rifles developed and manufactured by FB "Ã Âucznik" Radom. Early prototypes were known as the MSBS Radon.
The MSBS Grot was developed in two different configurations: MSBS Grot C (conventional design) and MSBS Grot B (bullpup design). Both configurations use the same locking mechanism, and the modular structure ensures interchangeability of parts and accessories. The MSBS Grot is intended to ultimately replace the FB Beryl as the Polish service rifle.
The MSBS-7.62N project began in late 2015, a designated marksman rifle variant based on the MSBS Grot, and was later designated as the Grot 762N.
The MSBS program was in development since 2007 by the Military University of Technology (WAT) in Warsaw with cooperation from the firearms manufacturer Fabryka Broni Radom, and was designed to replace the FB Beryl as the standard-issue service rifle of the Polish Armed Forces.
During initial tests conducted by the Military University of Technology, the MSBS-5.56 and its counterpart Heckler & Koch 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 fully automatic 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 main design characteristics of the MSBS-5.56 is the modular weapon system. If necessary, a soldier can sacrifice, for example, one standard assault rifle to quickly repair a light machine gun during a firefight. Another feature of the MSBS Grot is barrel changeability, as found on the Steyr AUG. This means a soldier may be able to adapt their rifle based on the environment they are in, such as converting a carbine to a designated marksman rifle, in order to engage targets at a greater range. The benefits of this feature allow an infantry squad to have fewer specialised weapons. MSBS may also be used with components other than the ones manufactured domestically, and it is the first Polish rifle fully compliant with the NATO standards. The MSBS-5.56 features fully ambidextrous controls and Picatinny rail, and it may also be fed from standard STANAG magazines.
Currently, the MSBS Grot is in service with the Polish Territorial Defence Forces and is scheduled to replace the FB Beryl as the primary infantry weapon and service rifle of the Polish Armed Forces. Following the adoption of the MSBS-5.56 by the Polish military, the Grot moniker has been added to the MSBS name in honour of the Home Army commander, General Stefan "Grot" Rowecki. The literal translation of the Polish word Grot is âÂÂarrowheadâ or âÂÂspearheadâÂÂ.
During the 2022 Russian invasion of Ukraine 10,000 Grot C16A2s were sent to the Ukrainian military.
On May 9, 2022, the public was informed about the conclusion of an agreement between the Polish Armaments Group and an undefined East African country for the supply of an unspecified number of MSBS Grot assault rifles chambered for 7.62ÃÂ39mm rounds as specified by the customer, along with 40 mm grenade launchers and optical sights DCM-1 Szafir manufactured by PCO S.A.
In January 2025, a photo appeared on the X website (formerly Twitter) showing small arms captured by soldiers of the Democratic Republic of the Congo from M23 rebels, amongst them is an MSBS Grot C chambered in 7.62ÃÂ39mm cartridge.
The MSBS Grot is a selective fire modular assault rifle which is capable of semi-automatic, 3-round burst and fully automatic fire. It has a cyclic rate of fire of around 700âÂÂ900 rounds per minute.
The MSBS-5.56 features fully ambidextrous controls and Picatinny rail, and it may also be fed from standard STANAG magazines.
Both the MSBS Grot C and MSBS Grot B are planned in 5 different configurations and have many common interchangeable parts and can be converted from one to the other:
The MSBS Grot B, and the machine gun and designated marksman rifle configurations are not yet produced. Conversion kits between variants are also not yet available. Conversion kit to change the calibre to 7.62ÃÂ39mm is available.
Since the Polish ministry of defence ordered 53,000 of the MSBS assault rifles, Fabryka Broni has introduced a military naming designation for the MSBS series.
Following the adoption of the MSBS-5.56 by the Polish military, the Grot moniker has been added to the MSBS name in honor of the Home Army commander, General Stefan "Grot" Rowecki.
The M2 was developed to address the issues found on the early production models. The bullpup configuration did not receive the M2 upgrade due to the lack of interest from the Polish military.
The changes included a longer upper receiver with M-LOK compatible handguard and heat stop covers, a quick-detach sling mounting points, FB made pistol grip instead of previous Magpul pistol grip due to shortage during mass production, reinforced buttstock, reinforced secondary sights, strengthened, thicker charging handle, reinforced firing pin (not interchangeable with the old one from M1), FB made polymer translucent magazine, new lock (not interchangeable with the old one from M1), and new slide (not interchangeable with the old one from M1).
The following variants were designed based on the requests from the Polish Armed Forces to replace currently used firearms such as the AKM, FB Beryl, FB Mini-Beryl, and Pallad grenade launcher.
The MSBS Grot C () is the classic configuration of the MSBS-5.56, chambered in either 5.56ÃÂ45mm NATO or 7.62ÃÂ39mm cartridge with a folding and retractable stock.
1,000 units were produced in the initial production of the MSBS-5,56 A0.
First production batch, also known as the âÂÂMSBS-5,56 A1âÂÂ: modified charging handle and additional strap mount point on the picatinny rail.
Second production batch, also known as the MSBS-5,56 A2: longer handguard to cover the gas block, reinforced firing pin for dry fire practice, improved pistol grip and buttstock.
The MSBS Grot A3 was publicly presented at the Grotowisko 2024 small-arms conference, held in Zegrze from June 22 to 23, 2024. Its development was based on lessons learned from the conflict in Ukraine.
The MSBS Grot R (Representative) is a manual repeating rifle variant of the MSBS Grot designed to be used as a ceremonial rifle by the Representative Honor Guard Regiment of the Polish Armed Forces, which has been adapted to fire blanks and withstand drills. With the modularity of the MSBS Grot, the barrel can be swapped to fire live ammunition.
The MSBS Grot S is a civilian semi-automatic only variant of the MSBS Grot that lacks the bayonet-mount, and is available in 4 different barrel lengths for the .223 Remington: 10.5-, 14.5-, and 16-inch and only in 16-inch for the 7.62ÃÂ39mm.
The MSBS Grot B () is similar to the MSBS Grot C but in bullpup configuration.
The MSBS Grot was designed to share a universal upper receiver for both the classic and bullpup configurations, which leads to the ease of conversion by simply swapping the lower receiver.
The Grot 762N is a semi-automatic designated marksman rifle chambered in 7.62ÃÂ51mm NATO cartridge, developed from the MSBS Grot.