These are stripped lowers and are uncoated blems. They are Armalite AR10 pattern and require that style upper. They will need anodizing or some other coating.
They are $79 each if you buy 3.
https://www.righttobear.com/DiamondBack-Armalite-AR10-308-Lower-Raw-Blem-p/db10-r-308-b.htm?Click=64422
I have a friend who is starting his gunsmithing business. He is looking for somewhere besides Brownells that carries the tools. Any suggestions on where to look?
This is what he sent when I asked what he needed.
"Fixing to shorten a barrel for a guy. Looking for barrel chamfering and facing tools along with muzzle radius tool."
I have made the same guarantee on several occasions and have yet to buy one from anyone. I have several in current rifles and one languishing in Arizona.
If you can wait a bit, there should be others online after they get off work. They may be able to give you some specific advice about the barrel you are looking at and recommendations for other choices to consider.
Also, do you have the M5 upper or is it an M5E? The M5E has a specific handguard that will fit it. The last time someone came through looking for one, they were out of stock.