I thought I would try switching over to 9mm today. I have an original Guide Lamp 9mm bolt and magwell insert along with an Indy Ordnance 9mm barrel assembly.
It did not work. Way too much headspace with this combo. Here's a short video showing the excessive space issue:
It appears that the barrel is just pressed into the trunnion (I see no pins or weld beads), so possibly I can take some measurements and have the barrel pressed farther into the trunnion to correct the issue?
Does that seem like a practical fix?