He pm'ed me with questions but can't post pics in pm, so here's the best I have from many combos.
1) Lyman data: I use 37 gr Longshot in new clear Fed. primed hulls from BPI
2) Use SOFT lead to cast. The harder the lead the worse your accuracy. Overfill bases with hot glue then trim even with base with warm blade after they solidify. Eliminates need for cards in wad. Use either Nobel Sport GTT1 or Trap commander wad. They are the same length and shotcup. The Nobel has a stiffer crush section and minimizes tilting, also cheaper and these are the ones I prefer but either will work.
3) 37 gr hand weighed Longshot powder. The book calls for up to 39. Here's what they look like in the charged hull.
4) top load with 1 clear plastic frangible OS card from BPI, and mine are started and finished on a Lee load all. The plastic is soft enough to make the crimp perfectly. You cannot set pressure with a load-all so get the feel of it. Easy.
5) Both loads fired at 50 yds. You absolutely cannot tell the hulls have been fired except for the spent primer. Perfect clean burn, no blow-by. Try as I might could not find the trap commander base but would look the same. Yes, petals ARE stripped but how could it be otherwise with thin shotgun wads in a rifled barrel? Base is perfect.
6) Out of 3" 870, 20" hasting cantilever rifled barrel, Nikon Slug Hunter bdc recticle at 50 yds. Typical crummy shotgun trigger. These loads drop about 6" at 100 yds, perfect for 1st ring down with this scope. Shot a 3" group at 100 yds last week in 10-15 mph crosswind, moved the slug about 8".
Good luck, that's the best I have. A deer or hog will not hold them.