Yup. "B MP 5.56 NATO 1/9". They look to be lightweight barrels.
Chrome lined bore and chamber with M4 cuts. The bolt carrier and key appear chrome lined (can't tell for sure, not as pronounced as my BCM BCG). Minimal wear inside the upper assemblies. I didn't pull the buffers or springs. I'll probably check those before hitting the range. Trigger assemblies look great and are a crisp 7 to 8 lbs without any creep (to this layman's touch). Pretty happy overall.
