OK partner, the first concern...
"Tennessee" style rifles are a sort of hybrid (imho) of the "Southern, Iron Mounted, Po' Boy" rifle. Traditionally they have a few characteristics. The obvious one is the slender stock with an elongated tang. Some have the "lollipop" tang, others simply have a long, thin tang, longer than any of the other rifle styles. They are simple, iron shod guns, often without a butt plate, and they tend to be at the small end in caliber, but with barrels from 42" or longer.
So one in .45 (with a 42" barrel) as was suggested is right.
Shorter and really large caliber isn't a "Tennessee" rifle..., now a Southern style possibly, but not really a Tennessee. I have found that .54 is very adequate for large game, and I like my 38" swamped barreled "Mountain Rifle".
What I'm talking about above though is strictly COSMETICS. It only applies IF...you want something that "fits" into the traditional styles as we group stuff today. That is up to you. Nobody can "forbid" you from doing what you want or need in your rifle.
IT IS NOT in any way intended to criticize your desires for a rifle. You are the fellow who has to carry it in the woods. You are the fellow who is going to target shoot with it, and perhaps hunt with it. You are the fellow who is going to handle the recoil when shooting, and finally you are the one who is going to pay for the parts and build it. :grin:
So yes, you can show up some place with a 36" .58 caliber, full stock, iron mounted rifle (yowza! :shocked2: ), and you may get some odd looks. Just remember, odd looks turn to smiles and pats-on-the-back when you shoot well at the range or down the deer. So get good parts, assemble them well, and then shoot that rifle a lot!
:thumbsup:
Now about barrels, calibers, and twists....
For the over-the-counter barrels that most of us buy to build, or have built into rifles... a 1:48 or slower twist rate is fine for patched round ball. 1:48 was very popular long before the conical bullet was popular; it's not a "compromise" twist rate. The slower twist rates can give you the ability to shoot some really stout loads, plus make cleaning a bit easier in some situations. I have barrels from 1:48 up to 1:66 and they all shoot patched round ball very well.
As for conical bullets, those same over-the-counter barrels tend to be a poor choice when the twist rate is slower than 1:48, but it's not just the twist rate, it's the manner of how the rifling was machined that counts. Since we're all buying from the same list of barrel choices, it's a good rule-of-thumb that slower than 1:48 isn't a good idea for a conical bullet.
I mention this detail as some folks get confused when they learn this rule, THEN they look at the specs of say a factory rifle like the Pedersoli Enfield, Richmond, or Springfield muskets. Reproductions of famous Civil War military "rifled muskets"..., they shoot conical bullets very well...and have twist rates as slow as 1:76 :shocked2: So... some guys get perplexed, as they learned slower than 1:48 = bad for conical; Pedersoli makes great conical shooting rifles in 1:66 and 1:76...and confusion sets in. Somebody is wrong....NOPE....the rifling in those Pedersoli rifles is designed for a specific conical bullet of a specific range of dimensions. :wink: The rule of thumb that we use still applies, but like all rules of thumb, it's not absolute....
So those are some of the consideration, and it's up to you to be pleased with the end result, not "us".
LD