I have just completed one of Dennis' Mathew Gillespies I can't say enough good about it. The only trouble I have had have been my mistakes.
In building a rifle you have got to overcome your mistakes. When you choose your own locks and triggers, you better be prepared to work that stuff out.....Making all this stuff work together is just rifle building.
Mr. Glazener's Gillespie Rifle Works and most of David Keck's (Knob Mountain...Fred Miller Patterns) are not really kits, rather, they are the basic parts to build up an authentic rifle. A rifle that otherwise would only be possible though a blank build/bench copy with the original on hand as the pattern.
Briefly here is is how it worked for me.
I had a 44" Colerain Bivins Barrel, a C wt in .54. Originally I had planned on a Rev War era rifle thus the profile. I contacted Dennis and we discussed his Mathew stock. I had admired that rifle for a long time and it was more appropriate for the time I reenact (Redstick War of 1814-14).
The original rifle had a wide breech so the Colerain was a good match for the stock.
Your 13/16 barrel may be better suited for Mr. Glazeners Harvey Gillespie Pattern. Mr. Glazener/Dennis is the one who can tell you for sure. I chose what wood I wanted from what Dennis had available. I chose Black Cherry and I then sent Dennis my barrel.
A couple of weeks layer my parts arrived. In the box was a Cherry stock with my barrel inlet and the ramrod hole drilled. It was pre shaped from the mid point of the lock panels back. From there forward to the muzzle it was in the square. Included was a set of Davis triggers, the Gillespie triggerguard, brass to make the pipes, ramrod tips, some hickory rods and screws and pins. I also ordered his Harvey Gillespie print.
I already has his Gillespie book. Over the next few years the rifle parts lived in the closet. I chose different locks and I even had a Pete Allen Percussion for awhile. I sold the Allen and finally chose a Davis Common with the gooseneck cock. I reshaped this lock.
I filed the breech tang to a point. Thinned the tang, reinstalled to the barrel, inlet the plug, bent the tang, inlet the tang and plug down, made the under lugs, one at a time I dove tailed them into the barrel and inlet them into the stock.
I was stuck for a while, put it away then I made contact with a rifle builder. He gave me some advise and hands on instruction(drilling pins) and at a session at his shop I started the lock inlet. I finished the lock inlet at home. Shaped the stock closer to profile and inlet the triggers. Here I made a mistake. I was little too forward with my set triggers and the Davis had a high sear bar. The curve of the stock confused me. I should have went straight up instead by the curve of the stock I was slightly too far forward....rookie mistake.
I then inlet the guard....it required almost no bending and fit well after just a little tweak.
Then it was all shaping with a pattern makers rasp, scrapers, chisels, files, a broken glass window pane and even some cheater sand paper.
The rifle has three screws and a lock bolt. The guard holds the triggers in and the barrel tang is held by a screw per original Gillespies.
So maybe that give you an idea of what to expect.
I really recommend David Rase's drill jig. I have a drill press but it's cheap and incomplete and a PIA to use except for basic drilling. I did not have for this build except for the vent. It's great for pins and lock bolts.
I bought the set in 2009. Life ect ect got in the way but really I have been heavy on the rifle since April I took a month or so off this summer.....to make sure I was not rushing it
So if you got after it steady.....3-6 months.
Most used tools, files, rasps pattern makers 50 and rat tail, but by far the 1/4 chisel.
Consider Dennis. In addition to his Gillespies he has a new pattern. A neat old SW Virginia Rifle?? that was built with a musket's trigger and guard.