FC Hook is another solution to make an AR-15 style rifle to comply with the restrictive legislation of some US states. It is a magazine catch with a built-in spring-loaded plunger which locks into the magazine well making the magazine release mechanism inoperable. With the FC Hook installed, once the magazine is inserted it gets locked in the lower receiver and can’t be removed without separating the upper and lower receivers. Here is a video showing the installation process.
Below I am quoting a part of a legal disclaimer from the manufacturer’s website which I think is important to know.
Use of the FC-Hook has not yet been proven to be an alternative to assault weapon registration and it has not yet faced a challenge by either the DOJ DROS process or case law. The FC-Hook has not been approved for use by the DOJ. The purchase and use of the FC-Hook requires an assumption of risk by the user’s with regard to the pending concepts of the FC-Hook’s ability to be an alternative to assault weapon registration. The FC-Hook still needs to prove its abilities to stand up to DROS and case law, or it needs to be accepted as common law by the California DOJ.
You can learn more about the FC Hook compatibility with legislation by visiting the Torque Precision website and contacting them.
The FC Hook is compatible with mil-spec AR-15 lower receivers. Probably the most significant drawback of this system is that it is not compatible with all magazines. Particularly, the magazines that have a raised rump over the magazine catch port, won’t work with the FC Hook. That makes it compatible with Gen2 PMAGs, but not compatible with Gen3 PMAGs.
According to Torque precision, they will soon release a magazine compatibility list as well as instruction video showing how to convert the non-compatible magazines to work with the FC Hook.
The FC Hook magazine catch is available through Torque Precision website at an MSRP of $39.99. If you want to buy the magazine catch button and spring with the FC Hook, you’ll need to add $3.8.