Something critical to consider when choosing an AR-15 is the gas system length…IE: carbine, mid, full. There are pros and cons to all three. While the carbine length is very popular for being light and compact, one issue that can cause some regrets is if you later decide to add a bayonet to your carbine length gas system on a common 16″ civilian-type carbine barrel. It will require a 1.5″ bayonet lug extender to fit correctly, which makes the strength and security of the bayonet mount questionable. Many folks will say their bayonet extender “works just fine” at holding the blade securely… but most of those folks have never actually used said bayonet in combat to know how much directional stress and rotational torsion it puts on the system. An adapter [below], held on with two tiny set screws does not inspire confidence. Just something to consider.
Bayonet Lug Extenders