Tell him if he could afford that semi auto just add a couple more thousand and get a Browning 725 28 gauge then there’s no need for that thing .
All my BS aside I had a similar thing I’d put on the ejection port of the AR’s I used for deer . Everything in an AR I had usually had pricey brass (Grendel , 260 , 338 Federal) so I didn’t take kindly to loosing even a single piece .