I need some help. I am going to start reloading slugs. I reload for my rifles and hand guns, but I have never loaded slugs. I am looking for a slug mold and reloading information for a 12 gage 100 yard load. I just got a new 870 with a rifled barrel so I don't have to use my smoth bore any more for Deer. The smoth bore gave me 5" groops at 50 yards off hand. I am looking for the same at 100 yards. Any help you can offer will be greatley help full. Thank you all for your time.

I have two suggestions for you.
First give Lyman's website a look I know for a fact that thay did sell the components to reload slugs such as a saboted slug mold and wads as well.
Second give Lightfield Slugs website a look. I know at one time thay also sold the components for reloading some of thier slugs.

Hope this proves helpfull.

I'd look into the Lee slug mold. It's designed to be used with a wad and have a star crimp.

I used to have a Lyman slug mold, it worked ok, but I wansn't too keen on having to try to roll crimp it. They also left a lot of lead in the barrel (mossberg - the barrels are pretty rough).

Another thing to consider is a round ball, my Lyman manual had data for them ages ago, but I don't have the manual anymore.

http://shop2.mailordercentral.com/bpicart/departments.asp?dept=198

http://www.ballisticproducts.com/

Check these guys out. I used to use a lot of their products, they have almost anything you can imagine for shot shell loading.

The Lee key drive slug in 12ga., 1oz is what i cast and loaded. First the lead has to be pure or the slug is hard to get out of the mould. I tried 2 load/wad loadings. The load data comes with the mould, and many different combinations of wads and powder. On average, group were in the 7" range at 100yards. I would get a flyer sometimes as much as 18" from point of aim, hurting the group averages. All slugs were checked for weight and flaws.Factory sabots in my mossberg cantilever scoped barrel run around 4" @ 100yds. I did notice one thing, once fired hulls were not as accurate as hulls fired a few times. It seems the hull can form to the chamber making a better, more accurate load. Shooting 5 shot groups at 100 yards.

http://xsorbit28.com/users5/slugshooting/index.php

Link to slug shooting/reloading. Hope it helps.