davidsng you asked for any tips or advice in your video I can offer 3 solid tips.
# 1 use a single shot tray when trying for 100 yard groups a magazine can
load your pellet or slug off center so that it is not centered in the bore, sometimes
it is better to hand load a slug and push it in with your finger.
# 2 Have someone with a lath cut the riffling in the breach end of your barrel if
your shooting a .217" slug use a chambering reamer at .217" cut it deep enough
that the riffling will just touch the slug when the bolt is in and locked into place.
# 3 Check and double check the crown make sure it is smooth and perfect sometimes
we hit the crown when we clean our barrels, with a perfect crown this ensures that
the slug leaves the barrel as true as possible, All of the things that I've mentioned can
make a difference in a barrel shooting ok or a barrel that shoots fantastic. Good luck,
very good shooting in your video the 24 gr Varmintknockers looked to be doing very well.