Hello all. I have a reoccurring problem with new builds, including brand new uppers straight from major manufacturers. Looking down the bore it appears that the barrel and hand guard are out of alignment. Any insight? Thanks

Face the front of the upper receiver before assembly.

Going to need a little more info. Brands, pics.

Short answer is, realign them.

Are we talking two piece gaurds with front sight bases? Or free float tubes?

If we could only see what you are talking about in some way....

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If you attach an optic, etc on top so that it grabs both the upper rcvr and handguard top rail, does it appear the upper rail and handguard rail are more or less perfectly aligned?

It helps to link the handguard to the upper as you do final tightening on the rail. I typically use a beater carry handle to bridge the gap and hold everything in alignment.

I've installed 15 or so, first couple weren't as good as the last 10, i went back and re-adjusted them.  You want them spot on for obvious reasons, the barrel nut is key on many.

A couple thoughts.

Could be an anomaly. Sometimes when tooling on the machines begins to wear out you'll find slight imperfections.

Always a good idea to square the upper at the extension prior to assembly.

This effect is called "potato chipping" by my rail mfg. When the screws / attachment system is tightened but they are not tightened equally or too much. Typically if you tighten 1 complete turn per screw until it clamps down you should be good. This is also why we are starting to see more clamping type attachment systems instead of 2 or three screws.

Good luck!