Matt1911
Cyrwus Jr.
So it also shaves weight to use a standard upper.Wall said:There are subtle advantages such as a smaller ejection port & lack of gas tube hole. These are places that won't be open to let trash come into the receivers, but it's not a must. Most 9mm receivers will be billet & styled better than a regular forged milspec receiver. In the case of the QC10 you mentioned, it is built (styled) to match the lower better than a 223 upper receiver.