Yeh. I'm gonna grab the shiney new barrel with a pipe wrench!
Actually, the barrel flats must be there, and in the correct place, so the rear sight block will clear that collar and the barrel and receiver will sit down into the stock on the stock crossbolt.
The barrel must be torqued onto the receiver with the collar intact and then marked at the receiver indexing mark. Then removed and machined.
I will post some photos. I will be working on it again this weekend.