My first impressions with the Bolt M16A4 AEG Blowback Airsoft Rifle where not so good as it was miss feeding and miss firing terribly for me. A quick communication with BOLT Airsoft and I was informed that perhpas my BB choice was the wrong one. The Bolt M16A4 AEG Blowback Airsoft Rifle has a true 6mm barrel so it is a tight fit with BB's that are 6mm since many can actually be a bit larger making them get stuck in the breach area. Read full article here: https://www.replicaairguns.com/2015/7/17/bolt-m16a4-aeg-blowback-airsoft-rifle-with-brss-recoil-field.html