Have you thought about casting the chamber with "cerosafe"? I purchased it from midwayusa to cast a t/c 357max barrel but a old off the barrel before using it. Once cast you can give the dimensions to ch for comparison.

After reading this old thread and having my buddy pull his hair out for a set of 257 TCU dies I figured I'd chime in.
Wes Ugalde didn't include the .308 in his TCU lineup.
Others did that after him.
Reeder has designed a line of Raptor cartridges utilizing the resurgence of 'longer' 204 Ruger brass.
I have been lucky enough to snag a 30 Raptor barrel for my contender.
Not a TCU but close
Here's the round next to a Blackout

I'm really impressed with it's performance and can't wait to do a little hunting with it

Sooooo, how many 30-223 variants does that make?
I recall (short to long):
Whisper/Blackout
Hamm'R
TCU
Raptor

Don't forget Joe Apache's 30 Apache!