.073 for a carbine gas 16''? That is pretty huge

What size did you end up ordering? I believe you order a size or 2 smaller than what you would want at the port due to the way gas drive works. I would think .060-.062 would be around where you want to be. Betting h2 or even h will run smooth.

Let us know how it works out. I love the inserts, might be ordering a tube for my uncle's gun