After thinking about it, i dont understand the need for hot swappable barrels on a tactical rifle. A light machine gun belt fed, yes. But nit a infantry or even "specops" gun. Swap the barrel you need to re zero the optics or sights. Better to just push two pins and change the upper for the new caliner if needed.
Solution looking for a problem that doesnt exist. I guess whoever is making that acr/scar furniture found a new sucker for their non-ergonomic designs
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." — L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...
"I crapped my pants to avoid the draft!!" -Ted Nugent