Nice gun at a good price. The date code is likely 2 letters near the proof marks on the underside of the barrel or on the barrel flats. It might be there by the serial #, I just can't see for sure in your photo. If it weighs just under 6-pounds it would be a 1970's era up to maybe early 80's. A bit over 7-pounds and it's mid-80's to current production. Since Replica Arms with the OH address dissolved in the mid-late 70's your gun must be from before that.
I have several, one is indeed marked Replica Arms. There's lots of info on how to load it. In short, you'll need powder, cards and shot. Ideally, you should get a shotgun scoop/measurer. I like the adjustable kind - Lee makes an inexpensive plastic adjustable one. For starters, use the same scoop for powder and shot. Very common in the 12-gauge is to set the scoop to 7/8, 1 or 1 1/8 ounce. Put a level scoop of powder in, a card or 2 or 3, then the same heaping scoop full of shot, followed by another card. The nipples use #11 percussion caps. Those are somewhat hard to find right now, but you can buy musket cap nipples in 1/4x28 thread. The old nipples should come out with a nipple wrench or the right sized small box wrench. Musket caps are more widely available than #11 right now in the market.
Lot of folks us different arrangements of wadding. You can literally take a 1/4 sheet of newsprint, crumble it up and mash it down over the powder, then add shot and put another wad of paper over the shot. Sometimes the paper will smolder on the ground after firing so beware. A couple of large green leaves would also work. A 3/4- inch round punch will make usable wads that you can punch out of a milk carton, posterboard or similar material, or leather or cork.
Use the SEARCH function here, check out V.M. Starr on a web-search or ask more questions for advice and opinions.
You can buy components at Track of the Wolf, Powder Valley, Midway USA, and plenty of other sources. Circle Fly is brand of pre-made wads. There's "nitro cards", "over-powder" cards, "fibre wads" and "over-shot" cards. You might want to eventually experiment with some combination of them, but it you just buy over-shot cards, you can put 3 or 4 on the powder and 1 on the shot. That'll get you shooting and then if you want to pattern the gun and tweak things you can play around with components. I load two 13-gauge .125 cards over the powder and 1 thin over-shot card on the shot in my Replica Arms Pedersoli for the best patterns.
Shotguns are not too picky about powder, so any black powder, Pyrodex or Triple 7 and others will work, just make sure it is BLACK POWDER or a bona fide BLACK POWDER SUBSTITUTE. The only brand that doesn't seem to work that good is Blackhorn 209, as it is made to be ignited by a primer, not a cap and it has a different formulation than the others.
