Beto lives in Texas. Texas has had a number of mass murders because of AR15 and Ak47. I own an AR15 and an AK47 along with other long guns. If there is gun control on these particular weapons, background checks, registration, much more difficulty in obtaining, psych evals required, magazine capacity, I wouldn't have a single solitary problem.
He's never proposed taking away traditional hunting rifles, shotguns or pistols. He hasn't advocated against personal carry.
The problem I have is the oversimplification of issues. A desire to end private possession of AR/AK styled weapons and reasonable ownership requirements is "taking away your guns". I reject that. A true conservative originalist interpretation (I am not one) or strict textualist interpretation (also not my groove) would lend to an erosion of 2A rights (if they were not political appointments) as nothing contemplates non-well regulated militia ownership of weapons.
Point is this, if your example of centrist matches Trump/Bernie supporters you are fringe, not center.