Sure.
The barrel gets pressed into the trunion with the bolt and a headspace gauge in the trunion.
Then, headspace is checked.
Then, the barrel gets drilled/reamed for a pin.
Now, you remove the barrel so that you can rivet the trunion into the receiver.
After that, you press the barrel back into the trunion until the pin hols is aligned perfecty, install the pin and do one final headspace check.