nice tip sundance44s! i don't remember if it was on 1/2 cock when i dumped the powder down, i'll follow your advice next outing (using the pyrodex rs this time).
went to the local shop & picked up a tin of cci MAGNUM #11 caps this time & some of that aerosol spray gun cleaner, kinda smelly, dries fast & turns stuff white (like acetone). used that to clean out the gunk by the breech/nipple, it's squeaky clean/dry now.
btw - i put a bright led white light in the nipple hole & tried to peer down the muzzle to see if i could see light coming through, i didn't - but i know the area is clean & clear of obstruction.
i keep reading on the internet that the investarms should take the .75mm nipple. i have a knight red hot 75mm nipple but the threads really don't look like the original nipple threads...the knight .75mm nipple starts to thread on tight, i will not try to force/wrench it down further.
.50cal ball - investarms nipple - knight .75 nipple - t/c 10-31 ramrod ball puller
here are the threads up close: investarms nipple - knight .75 nipple
what size would the original nipple be? the investarms manual does not say but the lyman's trade rifle manual does say .75mm...
that original nipple is not .75mm (don't look like it to me anyways).
just for kicks, i tried to see if the t/c 10-31 ramrod ball puller thread would fit but it's too small/narrow & it just drops right into the hole.
thanks gang, i really appreciate the tips.