I have progressed a long way since the last post on this thread 6 months ago.
I have gotten the BPI Roll Crimp Tool to work very well now and it produces very nice consistent crimps with a nice taper on the front of the shell to aid in feeding.
I have settled on 200 RPM's as the best operating speed but it is not super critical. It seems to be a balance between rotational speed and feed speed.
I have also made a new shell vise/clamp and I have to confess that I stole the idea from a guy on Youtube, we all watched his video a few months ago and he had several good ideas. It was simple to make and works really well, and costs almost nothing.
I am using my Milling Machine Spindle to crimp simply because it is there and easy to setup for crimping. It also lets me control the speed and depth of the spindle easily so I can try different speeds which is what I did until I settled on 200 RPM's as the sweet spot.
A few observations:
1. Previously Fold Crimped Hulls don't crimp as nice as Previously Roll Crimped Hulls.
2. Strait Wall Hulls roll crimp better than tapered hulls. IE: Cheaper hulls like Rio Cheddite, Fiocchi, crimp better than Winchester AA or Remington STS Hulls. New strait walled hulls crimp the best of all,,, and if you notice pretty much all Factory Loaded Slugs are loaded in strait walled hulls. Save your AA's ad STS hulls for Your Trap Loads.
3.Having a flat place for the crimp to seat on makes for better finished shells. Slugs with Flat Noses or Steps allow for more consistent Crimps. See Brenneke Slugs and Gualandi Thug Slugs as good examples. This design gives the Roll Crimp a good place to seat and produces more consistent ammunition. Note in the pics below that all of those slugs have flat faces for the crimp to seat on. Also note that the Factory Brenneke and Lightfield Slugs were loaded into normal Rio hulls. Nothing special and yet they are considered to be the best shotgun slugs available.
Believe me "anyone" can load ammo this good!
4. Overall lengths of the completed shells needs to be consistent for best accuracy. Wad pressure seems to be the primary variable here. If all your components are the same then all your loaded rounds should end up the same length as long as when you seat the wad it gets the same amount of compression from round to round.
Obviously the best way to do this is on a loading machine, however you can do it by hand by using a bathroom scale to push down on. You insert your Rammer (piece of 5/8" dowel) and push down on the wad to the same amount of weight each time. (This idea came from the Lee Classic Shotshell Loader instructions and it works just fine.) This will insure that the base of the shot cup in the wad is at the same elevation with relation to the base of the hull, and after the slug is introduced and the crimp closed the result should be rounds that are very close to the same length.
We take it for granted that our loaded brass cartridges all look the same. We know there are fine points that must be considered and many of us go out of our way to make sure that all our loaded rounds are as close to identical as possible.
Got news for ya,,, The same holds true for shotgun ammunition, only the fine points are a little different. Just stuffing a spent hull full of powder and shot will certainly shoot, but if you want rifle like accuracy out of your slug gun you are going to have to pay attention to some details.
Bottom line is whomever makes the best ammo, will probably shoot the best.
Randy