Brian your contribution is well received here. Well done. I might suggest some alternative views/methods only FWIW.
--obturation is the effect of ignition, inertia and accelleration on the slug. Depending on alloy hardness, this is realized on most cast bullets to some degree. BLK for instance does obturate thru 11-12 bhn [or 10/1 alloy]. It's a function of the time frame from first slug movement till muzzle exit against the profile of the pressure curve.
--lube cookies, methinks forget them. Yes some do manage to use them effectively-- but in the end all they do is cushion the initial combustion sequence adding another variable. BLK IMO is just a game of making the ignition sequence the SAME for each shot. Methinks the cookie complicates loading more than necessary.
--IMO use the newpaper wads IN those straight wall cases, especially if compression is major. Use hot primers too-- WLRM's, WLR, Fed 215 and Fed 210's.
--partial size your brass to the extent that loading that slug into the leade/rifling origin does not vary the loaded OAL. Important here-- that'd vary the ignition sequence of course affecting groups. I do believe setting that slug into the leade aligns the forward end of the slug also.
--lube....is the game in BLK. It has to flow. Beeswax is a nothing agent-- just the carrier of the stuff that does the work and helps plug the gaps per gas seal. JP works for some-- try beeswax with unsalted lard to the consistency needed for your temp conditions. Straight crisco works fine at colder temps.. The lube that flows and stays on the slug in 35 degree weather is about useless melting off that slug at 95 degrees. Lube for the most needs formulation to suit the conditions at hand.
--blow tubing is another critical factor for consistent accuracy. Can't be an afterthought process, refining the amount for the conditions at hand means good grouping. Too much the bullet wanders-- too little under tough conditions means fouling out and bullets everywhere.
--BLK cleanup is simple with water. If your load is working right, fouling is minor anyways. I normally fire a follow up shot or two with fad powder for removal of the most, wet with H20 and wipe and coat with Kroil-- a lite coat. Works for me and no rustin' yet.
--compression of the fuel depends, on how that lot number responds to your loading conditions. BLK will settle just fine metering the stuff straight into your case-- then hold that case tight to the metering mouth and tap that shell to settle. I use a hard composite screwdriver handle with the same sequence of taps each shell. The powder settles to the same point as if you'd used a tube... I compress with the seating die-- using a hard slug [heat treated in my case] with the driving band dia turned down. Compress- remove the dummy and seat. Simple and repeatable for OAL which is very important.
--the wad's job is gas seal- period. The breath of BLK is no different to the bullet base than 4759 or any other fuel. Keeping those combustion gases from going up the bullet sides is the thang. Tablet backing cut to a tight fit in the case is every bit as effective as any plastic wadding-- maybe BETTER. For it obturates also under the pressure more readily than harder plastic wads.
--beveling the cast bullet base is a refinement I'm trying. Some slugs come out depending on how the plate is fitting the mold block just a mite off level at the edges. It's minor-- but MAJOR at muzzle exit. I use a case deburring tool to lightly bevel that base edge. Don't affect wt-- if it shakes out as useful long term I'll see. High end mold would help this for sure.
-- just ENJOY the BLK... IT AIN'T COMPLICATED--- SOME JUST MAKE IT APPEAR SO.
