Yes, this BCG will work for a .350 Legend AR-15 rifle. "M16" simply refers to the mil-spec profile of the bolt carrier and does not restrict the type of AR pattern rifle it can be used in.
Any AR15 Bolt Carrier Group that is compatible with 5.56/.223 will also be compatible with 300 Blackout. So this Faxon Firearms 5.56/300BLK M16 Bolt Carrier Group would function as intended.
Yes, the Faxon Firearms 5.56/300BLK M16 Bolt Carrier Group will work for .223/5.56.
Yes, this is an M16 profile bolt carrier and has the proper length shelf for a full-auto sear trip. It is compatible with both standard full-auto trigger groups as well as multi-stage trigger systems like the FosTech Echo II
Yes, this BCG comes with a Mil-spec 5.56 bolt which is the correct bolt for 5.56/.223 as well as .300BLK and .350 Legend.
The weight of this product is 11.4 ounces.