.410 slug weight

the barrels on my 410(s) measure .387-.388 at the muzzle , full choked .
They are single shots and I use only brass hulls.
I have worked up loads using #9 shot in weights from 9/16- 7/8 oz weights.
All shoot well and are not in no way overpowered.
I use 2400 powder in different grains for different shot weights up to 14.5 gr.
I want to cast some RN slug loads for it and am thinking about a rifle type slug perhaps with a hollow base.
I see that the factory loadings for 410 slugs are very conservative from 1/5 oz up to less than 1/2 oz.
using a calculator or my digital weight scale a 9/16oz shot comes in at only 246 gr. 1/2oz is 219 gr.
What would a good slug load be and not be too much?
RT

.390 round ball of pure lead is the largest which you can depend upon going through the choke without bursting the barrel. I cut the muzzle off my .410 after I split the choke trying stuff like this. The remaining cylinder bore is .427" and .425" round balls shoot better in it than .44-40 Cowboy loads. You can load three .390 balls in a 2-1/2" shell with normal powder charge for your 9/16 oz. shot load. Any elongated, hollowbased projectile much heavier than the ball will be unstable from the smooth bore and you will have no hope of normal accuracy.

Attachment 190594
Attachment 190595

I ut open a Western 1/5 oz slug today and it was rifled and came in @.390 in diameter, the rifling was cast as lines at an angle around the sides with a rim around the bottom that was the large O.D.
It was hollow almost to the round nose.
I just wonder why such a light round? and I wonder what type of cherry cut such a mold?

Foster type slugs are form-stable like a badminton shuttlecock so the weight is forward and the finned hollow skirt provides drag to keep the nose forward and to ease the projectile extruding through the choke without bursting the barrel. These are not cast, but are cold swaged. The angled rifling does not rotate the slug, and is almost totally obliterated in the slug upsetting to fill the bore upon discharge and then being squeezed down through the choke.

I have seen high speed video of the rifled slugs spinning. Not much spin but just enough to make a little improvement in the accuracy dept. Fully rifled or even a rifled choke barrel would be better but the options for .410 are limited.

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Originally Posted by Outpost75

Foster type slugs are form-stable like a badminton shuttlecock so the weight is forward and the finned hollow skirt provides drag to keep the nose forward and to ease the projectile extruding through the choke without bursting the barrel. These are not cast, but are cold swaged. The angled rifling does not rotate the slug, and is almost totally obliterated in the slug upsetting to fill the bore upon discharge and then being squeezed down through the choke.

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Hollow base slugs fired from smoothbore shotguns usually have a length that is almost the same as the diameter. The short length coupled with the weight forward design allows the slug to fly without tumbling. If you want a longer/heavier 410 slug you will need an attached wad slug or a rifled barrel. Breneke sells loaded attached wad slugs for the 410, not sure if you can buy them as reloading components.

BB