FNH's FS2000 is an outstanding bullpup design, surely one of the best on the market. FNH incorporated into the design of the FS2000 a rubber gasket that seals the chamber and feeding when a magazine is inserted. This offers a dust/dirt-free aspect to the platform. Because of the FS2000's tight tolerances and sealed design, it will not accept popular polymer magazines. We do not recommend altering magazines or removing the rubber gasket from the weapon system. Your best option from the vast assortment of STANAG magazines are the steel magazines from Heckler & Koch (designed for SA80/MR556/HK416) Given the failure rate and poor design and manufacture of typical USGI STANAG magazines, we recommend these magazines and attest to the quality and reliability.