I'm a few steps ahead of you guys on my first gun, also a Chambers Isaac Haines. I removed the breech plug, inlet the barrel, then reinstalled the breech plug and inlet it again.
I ended up moving my barrel back 1/8 or so to be sure the touch hole liner would be just in front of the plug face, and the barrel went down just a hair as I inlet it. I used Prussian blue ink mixed in vasoline to do my inletting so far, but just ordered some inletting black as well.
I got all those videos and books but I'm still very nervous. I have the barrel in and pinned. The lock inlet and with working clearance, and the brass lock plate inlet, drilled, and lock drilled and tapped. Now I'm working on getting the trigger in and started moving thd buttplate forward the other day. I've been moving very, very slow. I have so many other things going on to boot, you guys will probably be done before I am.
I got the Davis double set trigger to put in instead of the one supplied with the kit. I don't know if you guys did this or not, but if you did, you may want to order a trigger guard with more room for the double triggers. Mine didn't look like enough so I ordered a wax cast Haines/Bivins trigger guard from Track of the Wolf yesterday.... upon the suggestion of an experienced gun builder friend. If anyone thinks they might run into the same situation, I'll get the exact model number when I get home.