Personally, for a complete rifle in that price range I would have bought one of the following: Ruger, S&W, or PSA, but that is not saying your DelTon isn't of equal quality. I just don't have much experience with DelTon personally, but they've been around for a long time.
Going off the specs on their website of the MLOK version of your gun, I assume they are the same (Model:
ECHO 316H), it looks like a good build from them.
Things I like to see they went with:
1. Carpenter 158 HPT/MPI'd bolt that is staked
2. Chrome lined carrier interior
3. M4 Ramps
4. Forged 7075 Lower and Upper
5. H Buffer
I don't particularly care for the 1:9 twist, chromed barrel, but it'll serve most fine, my preference would be a melonited 1:8 twist.
I would say you did well for $500.
The biggest question is the gas port sizing, which is a hidden item on all AR's as to how it was done at the factory. Where is your brass ejecting? Optimal ejection should be in the 3:00-4:30 and should reliably lock back on an empty mag with ammunition on the lower scale of power, I like to use Wolf steel for this. This is to insure it will have adequate gas to cycle whatever it gets fed.
Another item to watch is your extractor, but that is an easy and cheap upgrade if one needs with a better spring and o-ring.