How Have We made it More Reliable?
This is F5MFG’s 3rd generation redesigned version. It is one of the toughest 50 round drum for the MP5 tested and developed in over 4 years. We found that magwell dimensions vary from different manufacturers just enough to make precision machined parts fit loose in one manufacturer and tight in another (HK for example). This is why we designed and redesigned it to make a reliable feed function with an adjustable shim system. The shim system allows the magazine to fit perfectly well within the tight or loose magwell. The magazine tower is fitted with an aluminum shin system to give it a perfect fit for loose-fitting magwell. For tight magwell, you can remove the layers of aluminum shin until you reach the desired fitting. It can be done using a razor blade and picking one layer from one corner. The shims can also be replaced if needed.
Please note that we can not guarantee fit with out-of-spec clone firearms.