Lyman 12 gauge slug mold question

[boltaction308]

I got a Lyman 12 gauge slug mold recently that is missing the plug used to make the hollow base. I bought it because I have a lathe so making a new plug should not be a problem. The original plug has a round profile. Making a round profile is a bit tricky. Does anyone have a suggestion for a good profile other than the round one? I was thinking about making a truncated cone. I do have a complete mold as well. I got this one to experiment with and I am looking for where to start the experiments.

Thanks

[GabbyM]

Machinist tip.
Just rough your bar out with a 45 degree tool then use a 2nd cut mill file hand held to round it. Do not wear long sleeve shirt when doing hand work on a lathe. I ripped one off my Back once. Once was enough.

For the plug dimensions. I’d make it shorter than original to give a bit heavier nose.
As soon as the head length is bore diameter. Thus creating a situation where the choke has to crush a solid section of lead. You’ll have to size the slug loading as you would a round ball. Or else your choke would get opened up. Straight bore rifled barrel would be best. We were discussing this a few week ago in a thread.

[longbow]

If that is the Lyman Foster slug mould you have, I wish you luck! I have never been able to get mine to shoot well at all.

Just recently though after some discussions with a fellow who asked to remain nameless, I was advised that the biggest problem is that the wad column has to be "solid". His recommendation is to use a copper washer under the slug and on top of a hard card wad column. The extra support forces the slug to expand evenly into the hull/bore and center up properly. In case you have not checked these slugs cast well under bore size ~ mine casts at 0.705 and I have read of some people reporting more like 0.685". Now 0.685" could fit in a wad but 0.705" is too big for wad and too small for the bore.

Slugs recovered from snow show that the slugs obturate unevenly with the trailing edge of the skirt and nose being "cocked". SluggerDoug did a good write up on how he "knurled" slug up to bore diameter and got them to shoot quite well.

I couldn't find copper or brass washers of appropriate size so turned down some pennies to bore size and cast up some more Lyman Fosters to try one last time...

I would agree with a tapered TC profile for the pin and a little heavier nose being a benefit. Also, if you can machine driving bands on the slug I would open the mould up to bore size and thicken the skirt some.

As long as you don't make the nose too solid or thicken the skirt too much I don't think I would worry about a choke but GabbyM is right if you do make a solid thick nose down past the radius and thicken up the skirt especially if you open the mould up to bore diameter, that could be hard on a choke.

All in all, I have found that loading slugs into shotcups seems to give me better accuracy and is easier to load so that is the route I have gone. I was actually thinking of making a sizer for my Lyman Fosters to swage them down to shotcup diameter of about 0.680" but it was easier just to buy a Lee Drive Key slug mould. I haven't shot many yet but so far they shoot much better than the Lyman Fosters ever did and almost as well as round ball to 50 yards.

My $0.02.

Longbow