I've had good luck with both aero precision and PSA. Sometimes I use other barrels like black hole weaponry. An 18" rifle length with a mid to lighter weight barrel is one of my favorite all around combinations.

I'm currently putting together a 16" mid length and trying to decide on a good lighter weight barrel. I have aero M4e1 upper and lower, aero atlas s1 handguard. Triggertech adjustable trigger. I just need to pick a stock and barrel.

I just build two similar 18" guns in 6 arc and 223 wilderness. Both with aero m4e1s, atlas handguards, and triggertech adjustable triggers. The 6 arc has a gen3 prs fixed stock the 223 is adjustable carbine str or something. I used ballistic advantage varies on these and I'm not really impressed with the 6 arc yet but have only ran a few factory loads so far. One was moa but not much better. Loading should bring it in some.

PSA has the best budget brand kits etc IMO. There stuff works well especially for the price.

Bb