If anyone wants me to talk about more countries and make an article about my most recommended original antique guns, please comment below and I'll get to work with that article.
Info about antique firearms in the U.S.: http://www.rawles.to/Pre-1899_FAQ.html.
Laws on airguns and antique firearms:
Here, my top priorities are power and rate of fire, in that order. Your priorities may be a little different, but for me, practicality comes first.
For more details, and to see why I don't reccomend PCP or especially C02 for survival use, read http://www.ukpreppersguide.co.uk/best-air-rifle-for-hunting-and-survival-in-the-uk/.
For places that don't regulate types of airguns at all:
Most powerful spring rifles by caliber (smaller caliber rifles are legal in Illinois, South Africa, Finland and Estonia, all of which only have caliber restrictions, and they're also legal in New Zealand becuase they aren't PCP or full auto):
.177/4.5mm: Gamo Hunter Extreme SE.
.20/5.0mm: Beeman RX-2 Elite Series.
.22/5.5mm: Ruger Air Magnum Combo.
.25/6.35mm: Hatsan 125.
.30/7.62mm: Hatsan Carnivore 135.
Most powerful spring pistols:
.177/4.5mm: Browning 800 Express, Diana RWS LP8, Hatsan Model 25 Supercharger.
.22/5.5mm: Browning 800 Express.
As for how I find my most recommended airguns for places with power restrictions:
I use http://www.straightshooters.com/pellet-weights.html to make the following reference numbers:
.177: 15.74 grns.
.20: 25.00 grns.
.22: 27.50 grns.
.25: 31.02 grns.
Then I take this information and put it into http://www.airguns.net/calculators.php, then put in whatever critera, being caliber and muzzle velocity. With this system, you should be safe from legal consequences becuase these pellet weights are very heavy for their caliber.
For example, if I was looking for a Latvia legal rifle, I'd put in the 15.74 grn pellet weight and play with the FPS numbers until I get down into the legal energy limit. Then I put the information into Pyramidair.com that I'm looking for a rifle with a velocity between 450 and 500 fps. And that's how I found the Ruger Explorer
Rifles, caliber .177/4.5mm up to .25/6.35mm: Sumatra 2500, Air Arms S510 TC, Benjamin Trail NP XL, Ruger Magnum, Hatsan Model 125, SIG ASP MCX, AirForce Condor, Crosman Legacy 1000, Air Ordnance SMG-22.
Rifles, caliber .357/9mm to .50/12.7mm: Evanix Max-ML Bullpup, Evanix Rainstorm II PCP Air Rifle, Evanix Tactical Sniper Air Rifle, AirForce Texan, Hatsan Carnivore 135.
Pistols: SIG ASP P226, Browning 800 Express, Diana RWS LP8, Hatsan Model 25 Supercharger, Crosman 1377, the pistols listed on http://www.pyramydair.com/a/Air_guns/Air_pistols/162/cat_171/vel_400_0T410_0.
Machine gun: SMG 22.
Fully automatic BB guns I reccomend:
Compound: Excalibur Matrix 380 and Stryker StrykeZone 350, Hickory Creek Mini-crossbow.
Recurve: Excalibur Eclipse XT, Excalibur Matrix 330, Kodabow Takedown, .
Compound bows: Hoyt Carbon Spyder ZT Turbo, Hoyt Nitrum Turbo, and Mathews Monster Wake.
I would suggest using lighter weight bows if you are unable to effectively use these.
Canada (all spring rifles are in .22): Crosman M4-177 with Magpul storage stock, Weihrauch HW 95 in .22, Weihrauch HW 98 in .22 (does not come with iron sights), Cometa Fusion (does not come with iron sights), Webley Valumax, Hatsan Model 25 Supercharger in .22 caliber, Air Arms S410F Carbine Super-Lite .22 Cal,
Traditions arms sidelock, generic double-barreled flintlock shotgun.
Taiwan, France & India (4.5mm/.177 cal only) pellet guns:
.177/4.5mm: Walther Terrus, Walther Classus WS, Browning 800 express.
.22/5.5mm: Walther LGV Competition Ultra Air Rifle, Hatsan Model 25 SuperTact.
C02: Crosman 1077 Combo.
Germany flintlock musket: Traditions Arms .50 cal sidelock.
Ruger Explorer, Cometa Indian air pistol, Browning Buck Mark Air Pistol, Beeman HW70A, Gamo MP9.
.177: Crosman Raven, Cometa Indian air pistol.
.22: Hatsan Model 25 SuperTact, Hatsan Model 25 Supercharger.
United Kingdom & rifles for the Czech Republic: the airguns listed on https://duckduckgo.com/?q=%2212+ft%2Flbs%22+spring+site%3Awww.pellpax.co.uk&atb=v33-4__ . I would reccomend the Walther LGV, Crosman M4-177, and Weihrauch HW45.
United States, France, & South Africa antiques: Great Gun Eleanor, Uberti 1860 Army revolver, Uberti 1858 New Army carbine, 1863 Sharps rifle reproduction (not for South Africa), LeMat revolver reproduction.
Muzzleloading rifles and shotgun for South Africa: Pedersoli Coach Gun, Pedersoli Tryon Creedmoor, Pedersoli Gibbs Short Range Rifle.
Unfortinately, the Ultimate Firearms Tactical Muzzleloader (http://ultimatefirearms.com/tacticalmodels.php), modern shotguns fitted with muzzleloading barrels, the Thompson Center Encore, and other interchangeable barrel guns are not counted as an "antique" in the U.S. becuase the receiver can take rimfire and/or centerfire firing barrels.
Ultimate U.S. legal "antique" rifles:
Mauser 98, stripped down to nothing but the bare receiver, refurbished and has every other part replaced and .308 barrel installed in an Archangel AA98 stock.
But, becuase antique 1998 Mauser receivers is rare, I would suggest finding an antique Mosin-Nagant receiver (some Finnish Mosins have antique receivers) and doing the same to the Mauser rifle, with the addition of the Archangel AA9130 stock, using AA762R 02 magazines, and adding a muzzle break,
MINUS the .308 conversion becuase, from what I've read, .308 can not be safely fired in a Mosin Nagant (I'm not sure about custom aftermarket barrels though).
As for the barrel, I would reccomend getting it here: https://mcgowenbarrel.com/shop/full-custom-barrel/. Get it configured to be stainless steel, 16 inches long, bull barrel contour, flat dark earth cerakote finish, and muzzle break.
So I'd imagine that the rifle would look something like what you see in the video below. except with a stock that starts out OD green & barrel that is FDE brown then covered by multicam;
Delaware: IZH-Baikal MP-514K co2 BB rifle, Cybergun Jericho 941, Umarex Steel Force, Umarex Steel Storm.
Illinois: AirForce Condor (in .177), Benjamin Marauder, Benjamin Discovery, Gamo Hunter Extreme (all in .177 cal), Hatsan Edge in .25 cal, SIG ASP airguns, Evanix Max ML in .50 caliber.
Estonia, Finland & South Africa: whatever I listed that's BELOW .22/5.5mm.