If you want to eliminate something, then tax it out of existence.
A Federal tax on AR-15 ammunition could be passed in the Senate with 50 votes in a reconciliation bill because it is a revenue-raising measure that squarely fits within long-established budget reconciliation procedures.
Back in 1981, working with Bob Dove, the Senate Parliamentarian and Steve Bell, the staff director of the Senate Budget Committee, we crafted the first set of reconciliation rules and, while those rules have been modified, revenue raising measures are always permitted in reconciliation bills.
Moreover, a prohibition on self-made ammunition is permitted because the prohibition prevents everyone from avoiding the obligation to pay the tax.
This is how you instantaneously suppress the use of AR-15’s. You make the ammo too expensive to use. It’s not that complicated. Now, go out and find the 50 votes in the Senate to pass it.