MassMark
Member
Call or E-mail Jon at www.anvilarms.com
if you don't have much experience with the platform, i would suggest that you just buy one, and get to know the system and the inner workings with some good on hands experience and then worry about building one later.
The play between the upper and lower receiver in ARs is normal. After the break in period all ARs will have some play in them, once they are well worn they will rattle. This does not effect the action, or accuracy of the rifle.The DPMS is slightly cheaper but wobbles if you shake it.