I am looking to get a rifle to use during primitive weapon season. I currently live in Louisiana and if the rifle is a single shot, breech loading rifles or pistol, .35 caliber or larger, having an exposed hammer that use metallic cartridges loaded with black powder or modern smokeless powder it can take the place of a muzzle loader. I was contemplating getting a single shot 45-70 to use for hunting because I can use it through all of hunting season and can shoot any medium or large game in the US with that caliber. But I am graduating college in December and don't know what state I might end up getting a job in, so I wanted to know the laws for other states to see if it would be worth getting a single shot breach loading rifle or go with an inline muzzle loader.

Iowa - muzzleloaders have early and late seasons that are longer than the gun seasons. Gun seasons are shotgun but muzzleloader is OK and straight walled rifle like .45-70.  You can not use a 45-70 in the muzzleloader season even if you load the cartridge with 70 grains of black powder.  Rules will vary by state.  States may or may not allow in line muzzleloaders.  I have hunted with a TC muzzleloader  (Encore or Omega) for a long time with good success but run a wet patch down the bore after each shot because seating depth is critical to repeatability.  Gun seasons here are very short. Bow season last a long time.  To determine what to do you need to look at states you are considering.  If considering the Henry single shots I might go 44 mag rather than 45-70 because of a review where one gun had the stock replaced multiple times due to failure under recoil.
While you may think this will  be your buy once hunting rifle in all likelihood you will most likely buy others also.  Next a Tikka 30-06 or 300 WM or 300 WSM then a 22 mag and a Ruger American 7.62x39 because ammo is cheap and you get the idea....

In Idaho it's called "Primative Hunting Season". That refers to Muzzleloading season.

Why primitive you might ask,

No pelletized powder, loose grain only
No sabot, only minnie or round ball of lead only.
No 209 primers, musket caps, percussion caps or flintlock only
No inline rifles, only rifles where firing mechanism can be seen, such as flintlock or percussion.
No telescopic sights, only blade or peep.
No electronic sights allowed, fiber optic are OK.
Caliber for deer, mountain lion, antelope at least .45
Elk, Bear, Sheep at least .50

The “primitive weapon” season you are looking at is not going to be case with most other states.

Most “muzzleloader” seasons require, at a minimum, the projectile very loaded at the Bore, so any cartridge rifle is out.

Some states are more restrictive, not allowing things like sabots or enclosed primers or 209 primers or optics.

If you want something that will be most likely be acceptable for most Eastern muzzleloader hunting and a fair amount of Western muzzleloader hunting,  get a modern inline with 209 primer ignition.  You can shoot it with saboted projectiles in most places, and solid conicals in states that don’t allow sabots.  If you get a rifle like a CVA Accura, you can have both iron sights and mount a scope, so you have the option to hunt without optics.

If you buy a breechloading rifle, consider going in a caliber like .45-70 that would be legal in the rifle season for states that only allow straight wall cartridges.

Didn't they make a front-stuffer conversion for the 870 or 500?

That could be useful for a budget or space restricted hunter.

Then having a scattergun (possibly with rifled barrel) will allow gun hunting in any locale I've ever heard of for gun season.

I believe some parts of VA are buckshot only for example. But in NJ the go-to is 20ga lightfields (last I lived there). For most of ohio (and nj as far as I remember) you can get away with basic rifled slugs when in the woods.

In Ohio you can use anything for muzzleloader as long as you have to ram the projectile down the barrel. The ML season is only 2-3 days though, but of course can be used during the regular gun season (7 day) and the 2 day bonus weekend.

Honestly, I think archery equipment would be your best option. I'm not aware of any states that have legal issues with bows, and usually the season is plenty long. When woods hunting from a stand or blind, the firearm doesn't really do much more, IMO. It's just convenient.

I would think that it could be assumed that any .50 cal side hammer percussion/flintlock loaded down the muzzle using either a patched round ball or Miniball  would be legal in all states with a muzzleloader season.

NC states it has to load from the muzzle, no cartridge case, optics and inline are legal.  Can also hunt with muzzleloading pistols/revolvers.  I carry a 1851 .36 cal pistol with my side hammer, iron sight .50 cal Hawken type.  The Navy is for dispatching the water moccasins that are still out in the swamps I hunt.


CD

To the best ofmy knowledge your current muzzleloader/black powder season is very "liberal" and unusual.  Most such seasons require, at a least, an actual muzzle loader.  Details vary.   However, the vast majority are going to require something on the lines of an inline fronts stuffer.

a single shot breech loading 45-70 would be fine in regular rifle season in most states.  But its not going to fly for use in a primitive/muzzlloader/blackpowder season in the vast majority of states

Louisiana is the only state i've ever heard of that allows the use of metallic cartridge rifles to be used during "primitive weapons" season.  I have read on several other gun forums of guys using 35 Whelen out of TC Encore rifles or other single shot rifles.  The 35 Whelen would be great if you're going to live in states where you can hunt animals larger than Whitetail deer as well.  Nothing wrong with a 45-70 either other than the rainbow trajectory.  It's a great shorter range cartridge and works great in heavily wooded areas.  

Many western states are pretty strict when it comes to the definition of Muzzleloader.  It's why many non residents opt out of Muzzleloader season because their states allow inlines, sabots, pellet powders, and optics.

Pa has 2 different muzzleloader seasons.
Early October season is doe only. We can use inlines with scopes

The late December/January season is flintlock only. This season is fun but sucks if the weather isn't just right.

Here is what we are stuck with in our late season for firearms -

(1) Permitted devices. It is lawful to hunt deer during the flintlock muzzleloading deer season with a flintlock muzzleloading firearm. The firearm must be an original or similar reproduction of muzzleloading firearm manufactured prior to 1800. The firearm’s ignition mechanism must consist of a hammer containing a naturally occurring stone that is spring propelled onto an iron or steel frizzen which, in turn, creates sparks to ignite a priming powder. The firearm must have open sights and be a .44 caliber or larger single-barrel long gun or a .50 caliber or larger single-barrel handgun that propels single-projectile ammunition..

Us, and Mississippi (where we stole the idea from).

I use a CVA Scout in .35 Whelen, topped with a Weaver K6. It's a heavy booger, but quite accurate and has a great trigger. One day, I'd like to venture further into actual muzzleloaders; the current setup really just nets me an extra week on each end of the season.