So, after years of waiting for Armalite to actually make some flat top AR-10B uppers, I got tired of waiting, and cut mine off with a hack saw.
From there it went to my mill, using a custom upper holding mandrel.
Cut it down far enough to add a length of universal picatinny rail, that I machined to fit down over the upper.
And after drilling & tapping a bunch of little bitty threaded holes, I now have a flat top that matches the rail height of my other upper/barrel.

Was all the time worth it ?
Not if Armalite would have ever made some uppers.......But they never did.

Still have to LocTite all the screws.
The refinishing will come after I do a FAL charge handle conversion.
Have the handle, and just ordered the T-slot cutter.
Just need to order in some W1 tool steel to make the track that the handle will slide in.

Fantastic work and Holy Screws Batman!

Wow!

Sorta glad Armalite didn't get around to making the flat top.

Awesome job but not sure what the point of it is... you could have just bought something else. Armalite never made good rifles.

I don't have a unlimited budget.
Besides, I've always been able to take a black sheep, and turn it into a golden fleece.
That is why I have a machine shop in my garage, and why I became a machinist back in the early '70s in the first place.

And you are so right.
The barrel crown I found on this thing after removing the pinned muzzle brake was hideous.
Looked like a 12 year old had put it in using a 1/4" hand drill, and a countersink made for wood.
Only wish I had taken pictures before throwing the barrel in the lathe, and re-machining it.
So anyone with an Armalite that has a pinned on muzzle brake, should consider having it removed to check the crown.

Wow! Screws for days!

8 screws would've held just as well. Goodness, my base in my Rem 700 only has 4 screws...

Well, not quite.
The web between the lugs is only 1mm thick.
Had to be that thin in order to match the height of my other 'B' flat top, and still get a full 2mm of threads in the receiver.
Any hit to an optic which didn't end up right on top of a lug with screws in it, would have broken the rail.
So I had to secure each of the 22 lugs.

Anything worth doing, is worth over doing.  Better to be sure its solid than to half admit and take chances.  I like it!

That's the way Olympic Arms made flat-tops in the 80s, except with fewer screws.

Wow that is a nice job...how many hours do you have in it?

Hell, didn't even keep track.
Probably way more time figuring out how to do it, than actual machine work on the receiver.
Maybe a full day on the fixture to hold the receiver, then getting it indicated in, so the rail would end up parallel with the bore.
Kept running into road blocks, like finding a chunk of universal picatinny rail that fit my requirements, and how the heck to get the rail to the same height as my other -B receiver.

Wow, that's some great work. Reminds me of my old drag racing days when a part may not have existed or was way to much $$$. There was a guy at a local speed shop who was a wizard.

I'd say "can you make me one of those but to fit one of these" and he'd say "lemme think about it" A short time later there it would be, but better than I expected.

I don't have any milling equipment, etc. but more importantly I don't have the skills.

Didn't Oly leave a post of material to act as a recoil lug?

Pretty sure that was to keep the stock rear sight assembly.