Originally Posted by
polymorpheous
As long as the lower is within machining tolerances, (all the springs and pins fit where they are supposed to fit), you should be fine.
You can install a quality lower parts kit later, it is not as important as the upper.
The upper is the heart and soul of the rifle.
The bolt and barrel are huge in terms of the quality of the rifle.
Proper chamber dimensions, gas port diameter, and materials used are very, very important.
Parts ain't parts, and mil-spec is not the lowest bidder but the minimum standards that must be met.
Del-ton doesn't meet many of these minimum standards.
Buying a new upper is like buying a new rifle.
You can buy different uppers to serve different purposes.
For now, buy a quality bolt carrier group, (preferably with the heavier full auto carrier), and keep the Del-ton as back up.
Buy a heavier buffer as the Del-ton barrel is very likely over gassed.
Keep it well lubed and watch for signs of pressure when shooting 5.56 pressure ammo.