It's been around for a while and has received a bit of a tepid reception over the years, but the Bushmaster Adaptive Combat Rifle is a good option for shooters looking for a piston-driven AR variant.

The rifle was designed in collaboration with Magpul Dynamics several years ago when the company built what they considered the perfect AR. Dubbed the Magpul Masada, the rifle's main selling point was the fact that it enabled the user to quickly switch between calibers and barrel...