0.845" Handguard Cap?

[Crazy Chaingun]

Hello Nutters,

Just received the barrel for my AR build (DD 10.3" with FSB), and I'm stumped by something.

The barrel diameter directly behind my FSB is 0.845" according to my calipers. All the handguard caps I've seen for sale were either 0.750, 0.625, or 0.936. Anyone know where to find the right size? Google is failing me.

Or am I missing something here? First AR, I have much to learn.

Edit: It's also a govt. profile barrel, should they not be a standard thickness?
https://www.wolverinesupplies.com/P...HF-5-56-1-7-10-3--Barrel-Government-with-FSB-

 

[F22_RaptoR]

The handguard cap goes on the gas block portion of the barrel, it's sandwiched between the gas block and the shoulder on the barrel (not behind it), so you'll want the .750 handguard cap if it's a Gov. profile barrel with a .750 gas block seat diameter!

ETA

In that picture, if you click on the image and blow it up you can see a small gap between the shoulder and the front sight base. And that's the gap that your handguard ring will fit into

 

[Crazy Chaingun]

The handguard cap goes on the gas block portion of the barrel, it's sandwiched between the gas block and the shoulder on the barrel (not behind it), so you'll want the .750 handguard cap if it's a Gov. profile barrel with a .750 gas block seat diameter!

ETA

In that picture, if you click on the image and blow it up you can see a small gap between the shoulder and the front sight base. And that's the gap that your handguard ring will fit into

Well that makes perfect sense.
I am nominating myself for "World's Worst Gunsmith". Thank you!