Magnets or just attach it back there..
I dunno'.. it might be tricky to trust a magnet, I'd rather use a post or something and make a positive lock with it. Otherwise you run the risk of it falling, or someone grabbing it off your back and hauling ass with it.
However, if you decide to use a magnet, use 4 of them. Two positions on the rifle itself, and two positions on the back, to stop it from rotating.
If the magnet is too strong, it'll stop you from pulling off the rifle without risking damage. If it's not strong enough, and the backplate or rifle isn't adjusted to stop from slipping, it'll slip down your back enough to disengage the magnets if you jog it at all.
true...if i use a post system then it will make it really ez for someone to rip it off of me
i was thinking along of lines of a electric magnet. have a switch on the AR turn it off then the AR comes off the back, thats what we used in a show where we took a head off a dummie and put it on a table and we held it in place with a electric magnet, so it turn into a puppet