MFR Complete Upper
Does the MFR fit Mil-Spec and Billet Lower receivers?
Yes.
Does the MFR require any modifications?
Yes.
1 – You must install the supplied magazine catch and bolt catch extension.
2 – Must confirm that your buffer tube is Mil-Spec. If not, the carrier may hang up inside and cause the carrier to drag.
3 – Must confirm that the carrier is not in contact with the back of the lower receiver. If so use supplied spacers to adjust.
Does the MFR function with 62 grain and 55 grain?
Yes.