BRN-16A1 upper, Brownells retro 20" A1 barrel, flat slip ring, etc. Seated barrel, greased threads on the upper, tightened the barrel nut snug, loose, snug, loose, snug, then put the torque wrench on and set it for 35ft/lb...torqued until it clicked, checked gas tube alignment and while the tube did go in, it was canted to the left. Too far. Loosening it and setting it to 30ft/lb and trying again...still a little too far. I figure around 25-28lb got it lined up perfectly.

So...what do

I have another upper I can use instead, and it lines up at around 40ft/lb easy...but, the color doesn't match the lower, so I don't want to use that upper

I would turn that bitch to the next notch.  I doubt you'll exceed 80 ft./lbs.

There's almost no way it's going to get to the next notch at less than 100ft/lb...I can try, but that's how I warped one upper already, I think The upper that this was to replace, requires the rear sight be pinned all the way to the left and the front sight post bottomed out in the upper to get it near zero at 50 (not AT zero, NEAR zero...) That upper, I had overtorqued (I think) at least once

But, I'll give it a shot..I'll set my wrench to 80 and see how far it can get...

Use barrel shims, or lap the face of the receiver, and use the next hole in the existing barrel nut.   You may want to try a different brand of barrel nut.

Lapping the the receiver should also make the rear sight center up better, however why would you want a 50 yard zero ?   To remedy a bottomed out sightpost, I would simply file the front sight post shorter.

You can either face the receiver or shim it.  I've done both, but I prefer shimming since you don't run the risk of taking too much material off the reciever.  If your receiver is already on the short end of spec and your extension on the long end, you could end up with feed ramp overhang.  You can reprofile the barrel extension feed ramps but then that's another step.  You also keep the receiver original so you don't run into the same issue if you ever swap out the barrel.  Shims are quick and easy.  Just remember to cut a 1/16th of an inch section out of the shim.  The diameter of the shim will constrict under the pressure of the barrel nut and you need that 1/16th inch gap to allow the shim to constrict without bending or pinching itself.  This allows the barrel nut and shim to apply even pressure against the barrel shoulder.

Edit: I would not try wrenching it farther and risk over torquing it if you think you may have warped a different receiver that way.  I've torqued uppers to 100 ft/lbs and over without warping them and it is possible but I don't know your set up and it sounds like you may have had it happen once already.

A spare bolt carrier makes for a good gauge to test if a receiver is warped.  Just slide it in and see if it binds anywhere.  A tool like a Midwest Industries URR is even better since it's a tighter fit and can help detect more subtle warping.

Yep, send it.  Tighten, hold, loosen....a little more each time.  I expect 80# might be exceeded tho.

If OP has access to an upper lapping tool, it wouldn't hurt.

I doubt it will go to the next notch without going pasts 80 ft pounds. Shim, go past, or 4oo grit sand the receiver face anodizing a half thousandths or so if it wouldn't is what I have always done. It is surprising how taking some of the anodizing off without removing it all can change the torque value and alignment.

Because my range is only 100 yards, and a 50 yard zero pretty much gives you a 200 meter zero? Which I can't really check anyway?

I have the Brownells lapping tool and whatnot...I may as well give that a try later

I had the wrench set to 85ft/lb and it still didn't line up with the next hole, so it looks like I'll be lapping the receiver instead.

It takes very very little removal and it is extremely easy to remove more than necessary to get to the next notch at under 80. The tighten loosen and repeat method can work if there are just some high edges on the outside edge cuts on the upper receiver face.

This is why I like trying a shim first.  It doesn't permanently alter anything and if it doesn't work, you can still lap the receiver.

You guys are right on with the other options.  I never think about the shims because I've never used any, never needed them.  

But that, or lapping the face a bit, is probably a better technical approach to the problem.

OP, since you already have the lapping tool, yes, go for it.

And yes, you are right on track with the 50 yard zero.  It is most useful.

Shims are a lot simpler, if you have faith in the quality of your receiver.

Nice, ok, thank you all - I'll order a shim kit from Brownells...worst case, it's a good thing to have in the "what do" box anyway.

Even good receivers can have uneven ano on the face that only needs a slight touchup to clean up.  It isn't a bad idea to lap them all just for that.

Shims are good to have, tho.