Don't forget, a lot of the guys getting tight groups are pretty experienced and know their guns, loads, etc. How often you "swab" between shots (every shot? skip a shot?), the powder you use, how accurately you measure it out, how consistent you are with the depth and pressure you tamp in the bullet... there are a lot of variables. Little things like leaving your powder exposed to humidity longer than you should, or shooting old powder that's absorbed some over time... There's a lot to it.
I would say for a beginner, starting at 6" at 100yds is actually a decent start. I only got into this myself a few years ago and I'm down to 3" or so. I try to shoot at least 10 rounds a week, which doesn't sound like a lot but IMO, I think it's better to be very consistent about practicing over time rather than trying to sort it all out in a big day at the range. I know that's a common piece of advice for any firearm, but IMO muzzleloader benefits from more research than almost anything else. I'd shoot for a few days, then literally come here and comb through threads from folks talking about loads, swabbing, etc, then pick an adjustment to make in what I was doing and try that for a few more days.
