I've got a RRA detach carry handle with A2 sights mounted on a RRA flat-top upper (16" chrome-lined M4 bbl w/ no flash hider or muzz brk).  I shot both Wolf 62gr and some Winchester (nonQ3131A) 55gr and both have same windage POI, with the Wolf shooting a little flatter.  I was following the instructions for Santo's 50yrd IBZ and I have got the rear sight all the way over to the left and my shots are still about 1" right.  Now this is not some 1000yrd gnat shooter, and as long as the gun groups i'm happy.  I just wondered if anybody else has had the same experiance.  I think this weekend I will try and change my cheek weld, I was using nose to CH.

Copied from an old thread, might help ya:

[red]Gunsmithing TIPS from Chris: Barreling Uppers...
Installing a barrel is really pretty simple. Solving some of the problems you can run into isn't. Probably the most common problem is excessive windage present after the installation. [b]The rear sight will be cranked all the way to one side[/b]. This is one time the manual doesn't help much, most military armorer learn this trick early. [b]Here's how to fix it. Clamp the barrel in a vise, using barrel blocks. Line up the front sight carefully on a vertical line, just like the book says. First tighten up the barrel nut - hand tight, not torque to prevent damage to receiver. Now, look at your receiver. Chances are it's leaning off to one side -when compared to the front sight. Using a non-marring hammer, hit the side of the carrying handle, as near to the front as you can. This will rotate the receiver slightly to one side or the other. Here's the trick, hit on the side that the rear aperture is furthest away from. In other words, try to move the receiver towards the rear sight. Be careful, you don't have to kill it, just a firm tap will usually do the trick[/b]. If the barrel is straight, aligning the receiver forging with the front sight forging will usually put the windage adjustment right in the middle, and it takes about a minute to do it. Simple! One other trick we should mention is for when you are torquing on a barrel nut and everything locks up. A squeaking noise, then it's like it's welded right there. The surest way to break something is to keep trying to loosen it. This trick is so simple, we couldn't believe it. Put the whole assembly in the freezer, and leave it overnight. This gets some differential expansion working for you. Pull it out the next day, and it will almost always come loose. We recommend using an action block, like the one we sell, and clamping on the receiver to prevent breaking the index pin when doing this. A really good wrench, like the heavy duty one we sell, will prevent ruining the barrel nut.[/red]

Mike

im not sure what the proper tools are but ive tied fishing line to my front sight post then threaded it though the peep sight. clamp or tie something on the end of the line to hold it taught. then add a sinker or two to the line above the barrel to bow the line down so that a eye from above can easily see if the line runs down the center of the handle channel or off to one side.
-rifle must be level in a clamp :)

the above worked good for me

It could be the bbl is misaligned.  But I purchased this 'built' upper from one of the Arfcom Industry Partners because he has such a good rep, so my first inclination was that it was just an out of spec carry handle.  I will check for alignment tonight.  In the mean time, any other ideas?