As for authenticity, this sport is a re-creation of those cowboy shows and movies that many of our members fondly remember from thier youth. We're not a group of historical re-enactors, nor do we strive to be period correct as a general rule.
Each participant shoots the match the way they want to shoot it. Some like to shoot it as fast as possible, some like to shoot it as accurate as possible (I'm one of these), some like to shoot with only blackpowder loads.
Some like double barrel shotguns (double external hammers or internal hammers), some like lever action shotguns (Winchester 1887), and some like pump action shotguns (Winchester 1897). Some like to shoot Henry 1860 rifles, some like Winchester 1866 rifles, some like Winchester 1873 rifles, some like Colt Lightning rifles (pump action), some like Winchester 1892 rifles, and then some prefer the Marlin 1894 rifles. The really dedicated riflemen like to shoot the Spencer Repeater rifle, as you have to reload this rifle on the clock to finish the rifle sequence in most stages (only holds 8 shots in the magazine).
Now for pistols, we have the lovers of the percussion cap 'n ball pistols (Colt Walkers, Colt Dragoons, Colt 1855, Colt 1860, Remington 1858), the cartridge conversion open-top Colt revolvers, the 1873 Colt SAA revolvers (and its many clones), while others prefer the break top S&W Schofield revolvers. And let's not forget the Wild Bunch shooters, and the Colt 1911 pistol (and it's many clones).
We have soldiers, we have shopkeepers, we have saloon girls, we have soiled doves, we have lawmen, we have outlaws, we have western stars of the silver screen, we have cowboys, and we even have indians. It all comes down to how the shooter wants to play his or her own game.
IAC '97 Shotgun, Marlin 1894CB, Ruger Vaquero's, stock actions on all
Ruger New Vaquero's (stock actions), Tombstone Territorial Gunleather Cheyenne Rig
Ruger New Vaquero, 1885 US Cavalry Holsters, San Pedro Saddlery Shotgun Belt
1885 US Cavalry Sergeant, Campaign Uniform
SA 1911A1 GI (stock action), San Pedro Saddlery Pike Holster