This surface should be smooth. With the pressure on manufacturers, your AR could have similar defects which can and will produce malfunctions. Have your new rifle inspected and I’ll give it an ultra sonic cleaning as well.
AR 15 quality problems
Freedom Gunsmithing and Restoration
Licensed gunsmith. Customization including Cerakote, Micro Slick, trigger work parkerizing and rebluing. Conservation and restoration of antiques. No firearm sales or transfers.