Klvr PAL System
Bought 2 sets to try this out.
From their website :
Depressing your Kingpin PAL system does two things. In order to be compliant the takedown pin must first open the receiver. That is stage 1 of the PAL System. After the receiver is opened then you can legally release the magazine. That is stage 2 of the PAL System. Provided you installed your AR Maglock system correctly one press of the PAL System will activate Stage 1 first and then Stage 2 to execute a magazine change in your rifle. At no point prior to Stage 2 will you be able to release the magazine.