Starting a new build & I'm curious if any of you true up all your uppers prior to attaching the barrel?
I built my 1st AR without this step & haven't noticed any measurable problems with the barrel seating or lining up correctly.
Is it worth the 30 bucks for the tool?

Would you make a jig & perform the work in a drill press?

Edit:
Lapping Tool

First question is why???
What is the intended use for your build??
Are you satisfied with 1.5 to 2 MOA for the intended use of the rifle? That type of accuracy is with in the capabilities of commonly found unaltered parts.

IMHO the lapping tool is most useful to remove very small amounts of material off the front of the receiver to allow barrel nut alignment for the gas tube without exceeding the 80 ft-lbs of torque limit.

I'm not sure what I might end up building with the receiver set. I wasn't sure if it is a needed step in the process.
The reply in the second post actually is a reasonable purpose to lap the receiver.

I use the lapping tool on every upper I build and I have done over 40.  The only thing lapping does, that I can tell, is to make sure your sights zero near their mid range of adjustment.  None of my scopes or BUIS need to be cranked way over to one side or the other to zero, and I have used the lapping tool to correct situations where the rifle would only zero with the sights cranked all the way over so I know it works,  As to improving accuracy and increasing bolt life?  Cannot proove it by me.

I suppose it's a good tool to have. The time to use it is minimal.
Thanks for the input.

I've done 2 builds so far and have 2 more in various stages of completeness. I didn't use the tool on my first 2 and I have no plans to use one on the other. That said, if I had one at my disposal, I'd use it on every build. Use quality parts and the need for one drops. Gunshow special...I'd damn sure use one.

I've never done it, and never had a reason to.  I'm not saying there isn't a reason to, just that I haven't run into such a reason personally.

One school of thought about this process is that sometimes the anodizing on the face of the upper is uneven or excessively thick, which can prevent getting a barrel nut on the upper with acceptable torque.  Lapping the face of the upper evens that front surface, allowing easier and more consistent contact between the rear of the barrel flange and the upper, and allowing for more consistent torquing.

Another school of thought is that truing the face of the upper allows for a more exact fit between the barrel and the upper, which is supposed to help get the barrel more precisely centered.  This is probably how Big-Bore is getting his barrels installed with well centered sights, and might potentially help with a precision build.

Since I've never had an upper that I couldn't get a good barrel installation with, I don't think the "uneven finish" theory applies to more than a bare handful of uppers.  And the conservative technician side of me says "why remove ANY material when a 'hard to torque' barrel nut issue can be fixed by simply changing out the barrel nut?"  If I had issues with my sights needing a LOT of windage or elevation adjustment, I might consider tearing down the upper and lapping the front, just to see if it makes any difference.  Further, I might also lap an upper that I was using for a precision barrel build, merely to ensure that I had minimized all of the tolerances I could have any affect on.

Do this on every single build and/or any factory rifles you have. But because why? Because why not. I'm a firm believer in not half @$$ing things (even though technically I only halfway spelled that word...). But seriously, buy a PTG or another quality tool and use it early and often. Anyone who builds, buys, or bargains for an AR will at some point spend the amount of money on a part they don't want or like that would of covered the cost of the tool. Does it work? There's no empirical data to support it 100%. However, from a engineering standpoint it's very sound logic. There's a multitude of factors that go into accuracy, why not remove one from from the equation?

My precision AR shoots sub MOA or much better if I'm having a good day. Is it only because I lapped the receiver? Absolutely not! Does it not shoot sub MOA because the receiver is squared? Absolutely not!

I picked up a lapping tool because my sights were cranked to one side. Now I lap them all.

PS:  I too was skeptical but finally broke down and bought this Wheeler tool for my last build.  Both my current Aero Precision upper receiver and an older Mega receiver turned out to be slightly out of square at the front edge.  Whether squaring this interface makes a difference accuracy-wise is hard to tell, but when you are building your own AR, its nice to know your FF handguard is close to perfectly concentric to the axis of the barrel.

The Wheeler tool is best used with a handheld drill motor.  You need to increase the speed until the wobbling disappears.  I had to apply some fine sandpaper to the exterior of the section that fits inside the receiver, since it was too tight for my Mega receiver.  The cutting face started out kind of rough, but by the time I had lapped two receivers, it was smooth as glass.  Highly recommended. - CW