That's the plan. Only one for everything.
44", .54 cal. swamped & medium crowned LC Rice barrel with a Jim Chambers Early Germanic flintlock on a curly maple stock with forged iron furniture done in the Lehigh style (some carving and engraving). It will be THE ONE mostly because the others were sold off to afford it. Why? Because the original J.Rupp it is based on makes my socks roll up and down when I look at it.
I suppose if I was truly restricted to only one firearm of any type (breechloading or otherwise) I would have gone with a .58 smooth rifle.
In my shooting bag I carry:
Tin of patch grease ("antiqued" Kiwi 1 oz w/side lever opener)
Eight flints (7/8" English)
Two 36" x 1-3/4" strips of cotton tick
One 36" x 1-3/4" strip of flannel bedsheet for cleaning/oiling
Small wad of tow flax (initial cleaning w/water or spit)
One oz glass bottle of homemade "Moose Milk" w/cork
Small oil bottle (brass - WWI era from SMLE M1)
Turnscrew to fit lock & top jaw
Two metal vent picks ('forged' coathanger)
Flint awl
2" x 8" strip of leather (BIG aid in pulling a ball)
Five holer loading block (purpleheart)
Small antler-handled patch knife (on strap)
Vent feather (on strap)
Six inch strip of tick for wiping flint & frizzen (on strap)
27 ft (?? 25 meters) of 1/8" jute cord
25 to 40 cast round balls
Ball puller
Tow worm
Cleaning jag
Small folding knife
Second 5-holer loading block (walnut) w/ 1-1/2" stub starter on neck lanyard.
11" powder horn on seperate strap w/ a pound +/- of FFg
42 gr bone powder measure (two scoops is 84 gr)
75 gr antler powder measure
That's what I carry hunting, target shooting, hiking, etc.
I also carry a canvas haversack with lunch, license/permits/tags, deer drag, canteen, misc toiletries (aka a smushed partial roll of TP - I ain't a barbarian).
Sheath knife (forged coulter steel w/antler crown handle) and small pouch w/tinderbox on belt.
In car? Extra water and a Thermos of black coffee.
Whew! That was some question.