Without seeing it or shooting it I can't tell you much about your particular rifle-musket. But, I had one years ago and it shot about as well as any open sight rifle - that is, it shot as well as I could shoot. I seem to remember printing groups at 100 yards within the 4" range. There is a pretty wide range of results you can expect when trying to figure your best load, though. The "old style" 213 Minie ball (460 grns, I think) has a rather delicate skirt and it would deform easily at 70 - 80 grns. This caused some "keyhole" impacts that were well off the mark. I forget which bullet worked best but I think it was a 505 grn mammoth with a thick rear skirt ring. That one printed the best with 55-60 grns of 2F.
I imagine you could do better. Typically, these guns are more accurate with lighter charges. They can be extremely accurate for target work. Historically, the Remingtons didn't get too much service and I'm not sure why - maybe Mr. Chamberlin would know. But, reports of 600 yard shots during the Civil War included hits on any part of the enemy's anatomy. I doubt if very many of us could hit a garbage can at that range with a typical Zouave-type. However, at under 200 yards men would be slaughtered by the score. If, under 100 yards, you were in someone's sights - you were dead or dying. This is why they loaded and fired as fast as they could - whittle 'em down quick. I hope this gives you a view as to accuracy and power. These guns can shoot - some better than others, but they can shoot. Sharpshooters had their pick of rifles and usually they had a Springfield or an Enfield. The infantry was also armed with these but the sniper rifles were the pick of the litter.