Love the dedication you obviously have there! however do you have some emotional attachment to that Lee Loader? It must take hours. I have a MEC 600jr and I have it down to 45 min/25 regular shot shells - I can only imagine how long it takes with the slugs. BTW if you're interested in a progressive I know a guy...
2nd - do you know of anyone that makes slugs? Hummason maybe?
3rd - should the slugs be smooth or have rifling on them - unless you have a rifled barrel
4th - is it necessary to do the drill press thing? I know it looks more professional, but does it have any bearing on the ballistics? I'm thinking that you could use your stash of red AA for the slugs and the greys for the shot.
5th - have you ever tried Buckshot - I know a guy that has - but says it's very labour intensive..
Not OP but from my experience...
1. I have a MEC600JR and a Lee LA2; neither is any faster for slugs or buckshot since it still has to be hand placed. Even for birdshot the MEC will only be a little faster. The big advantage of the MEC is that it is so much better built and will last longer.
2. Several US companies make them, often with special wads specifically for them, but they are expensive and can't be exported from the US personally. Ballistic Products has a good selection and a Canadian distributor but it isn't much cheaper (if at all) than factory slugs. Finding someone who casts and is willing to sell you slugs is probably your best bet.
3. As said above the rifling is so they can swage through a choke. The pressure cone on the front of a super sonic slug (1100+ fps) will cause a low pressure area around the body with greatly reduced drag so even if the rifling is curved it wont cause much spin. Once the slug slows down it can cause very slight spin but this usually means doughnut patterns on target.
4. I have read that a roll crimp (which is what is done on the drill press) is superior to a star crimp but I've never noticed any difference. I use a normal star crimp on my slugs and can group just as good as factory roll crimped slugs out of a smooth bore.
5. I have loaded around 500 slugs and maybe 700 buckshot shells with cast 1oz Lee slugs and 00 buckshot. It's slightly more labour intensive to load buckshot than slugs. I can do a box of 25 shells in about an hour including buffer (powder mixed with the shot to prevent deformation; I use cream of wheat from Bulk Barn). Handloading buckshot also opens up a lot of options for your loads. I can load 8, 9, or 12 00 size pellets with or without buffer. My tests produced the best results with 8 pellets and buffer (pellets stacked by 2's in a shot cup). The pattern was about .8" per yard. With the pellets stacked by 3's (9 or 12 pellet loads) the pattern is about 1" per yard.
lee markets the slugs for rifled barrels
In my experience they work like crap in rifled barrels. I have tried all kinds of loads and things and have never gotten Lee key drive slugs to group even close to decent through a rifled 870. My guess is they just aren't big enough. Rifled 12ga barrels usually have a groove diameter of .730" and normal 12ga wads which Lee slugs are designed to go into only measure .705" to .710" so don't engage the rifling properly. Even if the base expands a little to engage, the part of the wad between the slug and barrel doesn't. At least that is my guess.
Most people who reload for rifled barrels use oversized single balls, full bore slugs, or buy plastic sabots that take jacketed bullets (usually large pistol bullets like .44 or .45). After trying everything I can think of and have found through hours of searching online and reading I just ordered a full bore slug mould. Only cost me USD$75 and shipping to Canada was all of USD$5 from Accurate Molds (handles extra, like all mould makers except Lee).