First off JN just because the manual says 79 grs is the most accurate that ain't necessarily so. Also what size balls are you shooting and what thickness are your patches? I would suggest using a .490" round ball and .015" thick patches to start. Also start with 80 gr (by volume) and work up in 10 grain increments. Swab the bore between each shot. You can use regular blue Windex on a patch and follow with a dry patch. Honestly you should be getting no less than 5" groups with your rifle if you're doing your part.

Watch this video for consistent ignition: