Are you properly following through on your shots? That is, ignoring that small explosion right in front of your face.
Check out
www.muzzleloadingforum.com. Be aware, these boys are hardcore traditional, don’t even bring up inlines or scopes. Best forum I’ve come across. X2 to order a copy of Dutch’s system. He’s a great guy and has forgotten more than most people will ever learn. He can be found on the above forum as well (known as Dr5x). Send cash, postal money orders don’t work when he tries to cash them and for some reason Canadians can’t use a credit card. When corresponding use large font, capitals or even bold type. He's having the dickens of a time reading with very poor eyesight.
I think you’ll find these are excellent sources to get started and I recommend you check them out before getting too far into it. I started off with my own research and learning on my own and while it was hugely enjoyable, these will help with the learning curve. If you can find a Black Powder match, a number of people who can give you more information than possible through posts or e-mails. You can find them in the Alberta Black Powder Association newsletter.
As far as shooting supplies, I’ve yet to find a truly great online supplier in Canada. Hillfolks in Saskatchewan seems to be well regarded but last time I checked they weren’t online. I have purchased from
https://www.trackofthewolf.com/Index.aspx and
www.thegunworks.com and can recommend both. Rustywood in Mission seems to be a good supplier of powder, never shopped with them.
Like reloading cartridges, a lot of variables to play with. Patch thickness, lube, type of powder and amount and even ball size as is relates to patch thickness.
For a .50, .490 is the most common size ball but you can get .495 as well. Get into casting or find somebody who does, commercial balls are not highly regarded and I've had no luck with them.
Spit patches can work quite well. Grease lubes like Bore Butter seem to be an iffy thing but some people are happy using them. Consistent lubing of the patch is necessary which is why something like Dutch's dry-lube system work well. Pre-lubed commercial patches may or may not work for you. Pre-cut patches are convenient but if you go to strips of patch material and cut at the muzzle you don't need to worry about an off-center patch.
Try different types, granulations and amounts of powder until you get results that satisfy you. GOEX seems to be the most common in North America but there are a few different ones out. FOR A FLINTLOCK,
ONLY USE REAL BLACK. Substitutes, even Pyrodex can lead to issues.
Blowing down the muzzle is a controversial subject. It helps any ember burn out out before throwing the next charge down. Safer method is to wipe with a spit patch and two dry patches which will also help remove fouling. I was also taught to wipe the bore after loading which makes no sense but again helps to minimize fouling build up. I've ended up wiping after every shot.
Have fun and make good smoke.